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The 2006 Leonid Meteor Shower: A Viewer's Guide

Fri, 17 Nov 2006 12:46:26 -0500

Mid-November brings us the return of the famous Leonid meteor shower, which has a storied history of producing some of the most sensational meteor displays ever recorded.

These meteors travel along the orbit of periodic comet 55P/Tempel-Tuttle, and whenever that comet is passing through the inner solar system, the Leonids have a chance to provide us with a dramatic show.

But the most recent passage of the comet to the Sun came back in 1998. We are now well past the favored time frame when, for several years running, observers in various parts of the world were witnessing very strong, even storm-level Leonid activity.

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The most recent Leonid storms occurred in 2001 and 2002.

That's why this weekend, when the Leonids traditionally should be at their most numerous, we normally would expect to see no more than 10 meteors per hour, even with the promise of excellent viewing conditions thanks to a New Moon on the 20th.

Still, for parts of Europe, Africa and eastern North America, a far more prolific Leonid show could be in the offing this year.

Judging the future by the past

On the morning of Nov. 17, 1969, an unexpected burst of Leonid activity was observed from parts of the eastern United States.

Meteor rates had been rather lackluster that morning until quite suddenly at around 8:50 GMT, Leonids began falling fast and furiously, with some observers reporting an average of two to four meteor sightings per minute. Peak activity apparently occurred within a few minutes of 9:00 GMT.

Then, just as abruptly as the surprising display began, it rapidly diminished until by around 9:20 GMT, things had pretty much returned to normal.

Most of the meteors that were observed were relatively faint, although as is typical of the ultrafast Leonids, there were several brilliant meteors, leaving persistent trains in their wake that lasted for many seconds.

What caught observers off guard on that morning thirty-seven Novembers ago was the Earth's passage through a very narrow trail of dust that had been ejected from comet 55P/Tempel-Tuttle back in 1932.

The densest part of that trail was probably about 30,000 miles (48,000 kilometers) wide, yet the Earth, traveling in its orbit around the Sun at 18.5 miles per second (29.8 kilometers per second), swept through it in only about a half an hour.

What to expect

In 1999, astronomers Robert McNaught and David Asher published a report concerning Leonid dust trails and cited the case of the 1969 outburst. They also forecast that in 2006 the Earth would encounter an adjoining section of that very same dust trail from 1932.

The time of this year's encounter is predicted for Nov. 19 at 4:45 GMT — 11:45 p.m. EST on Saturday, Nov. 18.

Other reputable meteor forecasters such as Thomas Van Flandern of the United States, Esko Lyytinen of Finland and Jeremie Vaubaillon of France confirmed in their own Leonid studies (to within minutes of McNaught and Asher's) that the Earth would indeed encounter the 1932 dust trail again in 2006.

But while another short-lived outburst seems probable this year, it likely will not be of the same intensity as what was seen in 1969. In that year, it had been about 4.5 years since comet 55P Tempel-Tuttle swept past the Sun.

But this November will be almost nine years since the comet last passed this way. So when Earth interacts with that same 1932 trail this year, the particles probably won't be as thickly clustered together as they were in 1969 and the resultant display might only be about half as strong.

Indeed, most forecasters are indicating that a sharp peak of perhaps 100 to 150 (mostly faint) Leonids per hour might be seen this year.

Where to see it

Those regions of the Earth that are in prime position to see another potential Leonid outburst are western Africa and western and central Europe, where the constellation Leo will ride high in the southeast sky as the peak of the shower arrives. Morning twilight will begin shortly thereafter.

In North America, for the Maritime Provinces of Canada, New England, eastern New York and Bermuda, the Sickle of Leo (from where the Leonids appear to emanate) will be above the east-northeast horizon just as the shower is due to reach its peak.

But because Leo will be at a much lower altitude compared to Europe, meteor rates correspondingly may be much lower as well.

However, this very special circumstance could lead to the appearance of a few long-trailed Earth-grazing meteors, due to meteoroids that skim along a path nearly parallel to Earth's surface.

Seeing even just one of these meteors tracing a long, majestic path across the sky could make a chilly night under the stars worthwhile.

Unfortunately, for the central and western United States and Canada, the Leonid outburst will likely have passed before Leo rises; at best, nothing more than the usual 10 or so Leonids per hour will likely be seen.

Keep in mind that for New England and U.S. East Coast, the peak is due locally on the previous calendar day, Saturday, Nov. 18, at 11:45 p.m. Eastern Standard Time.

For the Canadian Maritimes and Bermuda, the corresponding time is 12:45 a.m. on Sunday, the 19th. For Newfoundland it is also on the 19th, but at 1:15 a.m.

Preparing for your meteor watch

No two observers prepare for a meteor vigil the same way. It helps to have had a late-afternoon nap and a shower, and to wear all-fresh clothing.

Be sure to keep this in mind: At this time of year, meteor watching can be a long, cold business. Expect the ambient air temperature to be far below what your local radio or TV weathercaster predicts.

When you sit quite still, close to the rapidly cooling ground, you can become very chilled. You wait and you wait for meteors to appear.

When they don't appear right away, and if you're cold and uncomfortable, you're not going to be looking for meteors for very long! Therefore, make sure you're warm and comfortable.

Heavy blankets, sleeping bags, groundcloths, auto cushions and pillows are essential equipment. Warm cocoa or coffee can take the edge off the chill, as well as provide a slight stimulus.

It's even better if you can observe with friends. That way, you can keep each other awake, as well as cover more sky. Give your eyes time to dark-adapt before starting.

Probably the best bet is to rest on a lawn lounge chair, all the way back, so you can look up and see the whole sky.

When you see a streak, mentally run it backwards across the sky. Do the same with the second and third and note where their paths cross.

Right there will be the Sickle of Leo (with the bright planet Saturn also shining in that same general vicinity), and that's where the Leonid radiant will be.

Great Chance to Spot Planet Mercury

Mon, 27 Nov 2006 08:49:58 -0500

If there ever was a planet that has gotten an unfair reputation for its inability to be readily observed it would have to be Mercury, known in some circles as the "elusive planet."

Often cited as the most difficult of the five brightest naked-eye planets to see, because it’s the planet closest to the Sun, Mercury never strays too far from the Sun’s vicinity in our sky.

Mercury is called an "inferior planet" because its orbit is nearer to the Sun than the Earth’s. Therefore, it always appears from our vantagepoint to be in the same general direction as the Sun.

Thus relatively few people have set eyes on it; there is even a rumor that the great Polish astronomer, Copernicus, never saw it. Yet it’s not really hard to see. You simply must know when and where to look, and find a clear horizon.

And during these next two weeks we will be presented with an excellent opportunity to view Mercury in the early morning dawn sky.

In fact, if you’ve been an early riser this past week, it’s quite possible you might have stumbled across Mercury on your own.

Since Nov. 20, it has been rising at least 90 minutes before sunrise, which is also just about the same time that morning twilight is beginning.

If you scan low along the east-southeast horizon about 45 minutes before sunrise, Mercury has been visible as a distinctly bright, yellowish-orange "star."

The best views of Mercury, however, are reserved for this weekend, as Mercury will be rising more than 100 minutes before the Sun. This is even before the break of dawn, so for a short while at least, Mercury will be visible against a completely dark sky.

Its greatest western elongation—or greatest angular distance from the Sun in the sky—will come on the morning of Nov. 25, with Mercury standing a full 20-degrees from the Sun.

Mercury, like Venus, appears to go through phases like the Moon. Soon after it moved into the morning sky, Mercury was just a skinny crescent.

Currently, it’s appears roughly half-illuminated and the amount of its surface illuminated by the Sun will continue to increase in the days to come.

So although it will begin to turn back toward the Sun’s vicinity after Nov. 25, it will brighten a bit more, which should help keep it in easy view over the next couple of weeks.

By month’s end, Mercury will have increased in brightness to magnitude –0.6. On this astronomers scale, smaller numbers represent brighter objects and negative numbers are reserved for the brightest of all. Among the stars only Canopus and Sirius are brighter. And Mercury should still be relatively easy to find, low in the east-southeast sky about 45 minutes to an hour before sunrise.

In early December, Mercury will be joined by the planets Mars and Jupiter, resulting in an unusually tight gathering of the three planets on Dec. 10. On Friday, Dec. 1 SPACE.com will present a viewer's guide to this planetary trio.

Baseball Diamonds in the Night Sky

Fri, 20 Oct 2006 16:54:02 -0400

We're coming up on World Series time once again, so it may be of interest to baseball fans that there are two star patterns that very much resemble two baseball diamonds in our current evening sky.

Some sky watchers might immediately think of the Great Square of Pegasus , landmark of the autumn sky, as one of these celestial ball fields, and they would be right.

This week at around 8:00 p.m., the Square is high in the eastern sky. I know that many planetarium lecturers over the years have always referenced the Great Square as a baseball diamond (even though the "diamond" itself is in rather banged-up condition).

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The star Scheat in the upper right corner of the Square, would mark home plate. The star Alpheratz in the upper left corner of the Square marks first base (Alpheratz, in fact, actually belongs to the constellation of Andromeda, the Princess).

Algenib, in the lower left corner of the Square is second base, while Markab in the lower right corner is third base.

If your skies are reasonably dark, you'll be able to see two fourth magnitude stars — Tau and Upsilon Pegasi — both inside of the Square, and roughly one-third the distance from Scheat to Algenib.

Perhaps we might imagine this stellar pair as the pitcher having a conference with his catcher just out in front of the mound.

Meanwhile, waiting behind home plate is the umpire, marked by the star Eta Pegasi.

Finally, another pair of stars — Lambda and Mu Pegasi — can be found just off of the third base line. Perhaps we could imagine that here is the batter getting some instructions from the third base coach.

But a far better configuration for baseball can be found in stars that lie overhead and toward the west.

Astronomer Henry Neely (1879-1963), who worked at the Hayden Planetarium and who was known as the "Dean of New York Stargazers", invented this pattern nearly sixty years ago.

Study the stars of Cygnus, then check the map to find Neely's baseball game.

The batter (Deneb) is facing the pitcher (Sadr) and has hit a fly to center field. Albireo is running in to get it and second baseman Phi is also out after it. Shortstop Eta has run over to cover second for Phi.

Perhaps Deneb is a left-handed power hitter, since left fielder Vega plays normal depth, but Altair is quite deep in right-center. Meanwhile Epsilon is at first base, while Delta patrols the "hot corner" at third.

Of course, if you ever point out either of these celestial ball fields to members of your family or friends, you might want to substitute the star names for the names of the players on your own favorite baseball team.

You can even embellish the concept of this star pattern by doing a little play-by-play.

As an example, when describing the baseball game to his planetarium audiences, Neely would sometimes point to a close pair of stars near to Deneb (Omicron and 32 Cygni) commenting:

"Well, it looks like there's some controversy brewing ... I see the manager having an argument with the home plate umpire."

Neely would always finish his baseball discussion by sweeping his electric pointer around the sky with a flourish and noting, "It must be an important game being played tonight ... Why, just look at all the people who showed up!"

Astronomers Patiently Wait for Star to Go Nova

Fri, 22 Dec 2006 15:22:25 -0500

At this time of year it seems almost traditional for stargazers to ponder the age-old question of the origin of the Star of Bethlehem.

The star's appearance some 2,000 years ago is quite possibly one of the best-known celestial events in all of recorded history.

Many planetariums are currently running sky shows interwoven with a Christmas theme.

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Utilizing special effects projectors, audiences are transported back in time to see the night sky as the Magi may have seen it and are then asked if perhaps an unusual gathering of planets might have been the fabled star.

Or was that "sign" a comet, a nova or something supernatural?

The topic has universal fascination, and is why Christmas Star shows still play to packed planetarium houses.

Perhaps the simplest answer that can be offered is that the Star might have been a nova — a "new star" suddenly blazing forth where no star had previously been seen.

While for the most part such objects are really dying stars having a final fling of glory before descending the long road to ultimate extinction, there are some stars that go through such contortions more than once.

One such star is long overdue to "pop," and could do so at anytime.

The star in question is T Pyxidis, in the constellation of Pyxis, the Mariner's Compass, a dim southern constellation that never gets very high for skywatchers in the United States.

For instance: As seen from Philadelphia, Indianapolis and Denver, it reaches a maximum altitude of just 18 degrees above the southern horizon (your clenched fist, held at arm's length, is roughly 10 degrees in width).

Currently, Pyxis is crossing the meridian around 2:30 a.m. By the end of January it will be there just after midnight and by early March, just before 10 p.m.

T Pyxidis is about 6,000 light years away and belongs to a small and seemingly "exclusive" group of cataclysmic variable stars called recurrent novae, of which there are currently less than 10 confirmed members.

T Pyxidis is composed of a dense white dwarf and a close companion star.

An outburst occurs when the temperature and density of the surge of matter dumped from the companion onto the surface of the white dwarf reach the nuclear flash point for hydrogen.

While material is violently blown off in all directions, the white dwarf itself is not disrupted. It soon begins to accumulate more matter from its companion and repeats the cataclysm some years later.

Astronomers have been patiently waiting for T Pyxidis's next outburst for more than 20 years.

Normally this star shines at magnitude 14 — that's about a thousand times dimmer than the faintest star that can be perceived by most human eyes on a dark, clear night.

But on five occasions, in 1890, 1902, 1920, 1944 and 1967, this star brightened dramatically to magnitudes between 6.5 and 7 — a 1,000-fold increase in brightness in the most extreme case — making T Pyxidis just bright enough to be glimpsed without any optical aid.

These eruptions came at an average of just over 19 years apart, and the longest stretch of time between them was 24 years.

But this month marks 40 years since the last outburst.

It was back on Dec. 7, 1966 that the most recent eruption was first noticed by New Zealand amateur astronomer Albert Jones.

The star had more than doubled in brightness to magnitude 12.9.

Just two nights later it was almost four magnitudes brighter, and after a month it was glowing at magnitude 6.3 before slowly fading back to normal.

Nobody knows exactly why T Pyxidis has remained quiet for so long, but the general consensus is that it may have accumulated an extra-thick coating of nuclear fuel on its surface over these past 20 years, which would make it appear extra bright when it finally blows its next surge of gaseous debris out into space.

Who knows? That night could be tonight!

Week-Long Geminid Meteor Shower Starts Sunday

Fri, 08 Dec 2006 15:09:58 -0500

The annual Geminid meteor shower is expected to produce a reliable shooting star show that will get going Sunday and peak the middle of next week.

The Geminid event is known for producing one or two meteors every minute during the peak for viewers with dark skies willing to brave chilly nights.

If the Geminid meteor dhower occurred during a warmer month, it would be as familiar to most people as the famous August Perseids.

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Indeed, a night all snuggled-up in a sleeping bag under the stars is an attractive proposition in summer. But it's hard to imagine anything more bone-chilling than lying on the ground in mid-December for several hours at night.

But if you are willing to bundle up, late next Wednesday night into early Thursday morning will be when the Geminids are predicted to be at their peak.

Most satisfying shower

The Geminids are a very fine winter shower, and usually the most satisfying of all the annual showers, even surpassing the Perseids.

Studies of past displays show that this shower has a reputation for being rich both in slow, bright, graceful meteors and fireballs as well as faint meteors, with relatively fewer objects of medium brightness.

Many appear yellowish in hue. Some even appear to form jagged or divided paths.

Unfortunately, as was the case this year with its summertime counterpart, this year's December Geminids will be hindered somewhat by moonlight, although to a much lesser degree than the brilliant gibbous Moon that wreaked havoc with the Perseids.

On Thursday morning, the Moon — a fat waning crescent, two days past last quarter — will come up over the east-southeast horizon by 1:30 a.m. for most locations and will light up the sky in its general vicinity through the rest of the overnight hours.

On Friday morning, the Moon will come up about an hour later and will be less of a factor for meteor watching.

Where to look

These medium speed meteors appear to emanate from near the bright star Castor, in the constellation of Gemini, the Twins, hence the name "Geminid."

The track of each one does not necessarily begin near Castor, nor even in the constellation Gemini, but it always turns out that the path of a Geminid extended backward passes through a tiny region of sky about 0.2-degree in diameter (an effect of perspective).

In apparent size, that's less than half the width of the Moon. As such, this is a rather sharply defined radiant as most meteor showers go; suggesting the stream is "young" — perhaps only several thousand years old.

Generally speaking, depending on your location, Castor begins to come up above the east-northeast horizon right around the time evening twilight is coming to an end.

As Gemini is beginning to climb the eastern sky just after darkness falls, there is a fair chance of perhaps catching sight of some "Earth-grazing" meteors.

Earth-grazers are long, bright shooting stars that streak overhead from a point near to, or even just below, the horizon.

Such meteors are so distinctive because they follow long paths nearly parallel to our atmosphere.

By around 9 p.m., Gemini will have climbed more than one-third of the way up from the horizon. Meteor sightings should begin to increase noticeably thereafter.

By around 2 a.m., Gemini will stand high overhead.

Because Geminid meteoroids are several times denser than the cometary dust flakes that supply most meteor showers, and because of their relatively slow speed with which they encounter Earth (22 miles/35 kilometers per second), Geminid meteors appear to linger a bit longer in view than most.

As compared to an Orionid or Leonid meteor that can whiz across your line of sight in less than a second, a Geminid meteor moves only about half as fast.

On a personal note, their movement reminds me of field mice scooting from one part of the sky to another.

When to watch

The Earth moves quickly through this meteor stream, producing a somewhat broad, lopsided activity profile. Hourly rates will start increasing on Sunday night (Dec. 10), appearing roughly above one-quarter peak strength.

Late Wednesday night up until early Thursday morning when the Moon rises, a single observer might average as many as 60 to 120 meteors per hour.

After Wednesday night, the rates are expected to drop off more sharply: The rates on Thursday night/Friday morning will have diminished to about 30 to 60 per hour.

Yet, there is good reason to keep watching for Geminids even after their peak has passed, for those "late" Geminids tend to be especially bright. And renegade late stragglers might be seen for a week or more after the night of maximum activity.

I brought this up this point earlier, but certainly it should be addressed again: Make sure you're warm and comfortable. Likely your local weather will be more appropriate for taking in a hot bath as opposed to a meteor shower!

Warm cocoa or coffee can take the edge off the chill, as well as provide a slight stimulus.

A final point to note are that Geminids stand apart from the other meteor showers in that they seem to have been spawned not by a comet, but by 3200 Phaeton, an Earth-crossing asteroid.

Then again, the Geminids may be comet debris after all, for some astronomers consider Phaeton to really be the dead nucleus of a burned-out comet that somehow got trapped into an unusually tight orbit.

Best Meteor Shower of 2007 Peaks Dec. 13

Tue, 11 Dec 2007 07:22:31 -0500

What could be the best meteor display of the year will reach its peak on the night of Dec.13-14.

Here is what astronomers David Levy and Stephen Edberg have written of the annual Geminid Meteor Shower: "If you have not seen a mighty Geminid fireball arcing gracefully across an expanse of sky, then you have not seen a meteor."

The Geminids get their name from the constellation of Gemini, the Twins, because the meteors appear to emanate from a spot in the sky near the bright star Castor in Gemini.

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Also in Gemini this month is the planet Mars, nearing a close approach to the Earth later this month, and shining brilliantly with yellow-orange hue.

To be sure, Mars is certain to attract the attention of prospective Geminid watchers this upcoming week.

Reliable shower

The Geminid Meteors are usually the most satisfying of all the annual showers, even surpassing the famous Perseids of August.

Studies of past find the "Gems" have a reputation for being rich both in slow, bright, graceful meteors and fireballs as well as faint meteors, with relatively fewer objects of medium brightness.

They are of medium speed, encountering Earth at 22 miles per second (35 kps). They are bright and white, but unlike the Perseids, they leave few visible trails or streaks.

They are four times denser than most other meteors, and have been observed to form jagged or divided paths.

Geminids also stand apart from the other meteor showers in that they seem to have been spawned not by a comet, but by 3200 Phaethon, an Earth-crossing asteroid.

Then again, the Geminids may be comet debris after all, for some astronomers consider Phaethon to really be the dead nucleus of a burned-out comet that somehow got trapped into an unusually tight orbit.

Interestingly, on Dec. 10, Phaethon will be passing about 11 million miles (18 million kilometers) from Earth, its closest approach since its discovery in 1983.

The prospects for this year

The Geminids perform excellently in any year, but British meteor astronomer, Alastair McBeath, has categorized 2007 as a "great year."

Last year's display was hindered somewhat by the moon, two days past last quarter phase. But this year, the moon will be at new phase on Dec. 9.

On the peak night, the moon will be a fat crescent, in the south-southwest at dusk and setting soon after 8 p.m. That means that the sky will be dark and moonless for the balance of the night, making for perfect viewing conditions for the shower.

According to McBeath, the Geminids are predicted to reach peak activity on Dec. 14 at 16:45 GMT.

That means those places from central Asia eastwards across the Pacific Ocean to Alaska are in the best position to catch the very crest of the shower, when the rates conceivably could exceed 120 per hour.

"But," he adds, "maximum rates persist at only marginally reduced levels for some 6 to 10 hours around the biggest ones, so other places (such as North America) should enjoy some fine Geminid activity as well."

Indeed, under normal conditions on the night of maximum activity, with ideal dark-sky conditions, at least 60 to 120 Geminid meteors can be expected to burst across the sky every hour on the average. (Light pollution greatly cuts the numbers.)

The Earth moves quickly through this meteor stream producing a somewhat broad, lopsided activity profile.

Rates increase steadily for two or three days before maximum, reaching roughly above a quarter of its peak strength, then drop off more sharply afterward.

Late Geminids, however, tend to be especially bright. Renegade forerunners and late stragglers might be seen for a week or more before and after maximum.

What to do

Generally speaking, depending on your location, Gemini begins to come up above the east-northeast horizon right around the time evening twilight is coming to an end. So you might catch sight of a few early Geminids as soon as the sky gets dark.

There is a fair chance of perhaps catching sight of some "Earth-grazing" meteors.

Earth grazers are long, bright shooting stars that streak overhead from a point near to even just below the horizon. Such meteors are so distinctive because they follow long paths nearly parallel to our atmosphere.

The Geminids begin to appear noticeably more numerous in the hours after 10 p.m. local time, because the shower's radiant is already fairly high in the eastern sky by then. The best views, however, come around 2 a.m., when their radiant point will be passing very nearly overhead.

The higher a shower's radiant, the more meteors it produces all over the sky.

But keep this in mind: At this time of year, meteor watching can be a long, cold business. You wait and you wait for meteors to appear.

When they don't appear right away, and if you're cold and uncomfortable, you're not going to be looking for meteors for very long!

The late Henry Neely (1878-1963), who for many years served as a lecturer at New York's Hayden Planetarium, once had this to say about watching for the Geminids: "Take the advice of a man whose teeth have chattered on many a winter's night — wrap up much more warmly than you think is necessary!"

Hot cocoa or coffee can take the edge off the chill, as well as provide a slight stimulus. It's even better if you can observe with friends. That way, you can keep each other awake, as well as cover more sky. Give your eyes time to dark-adapt before starting.

Bundle up and good luck!

'Great Show': Perseid Meteor Shower Peaks Sunday Night

Fri, 10 Aug 2007 17:55:16 -0400

Every August, just when many people go vacationing in the country where skies are dark, the best-known meteor shower makes its appearance.

The annual Perseid meteor shower is expected to be at its best this year, producing one or two meteors per minute during peak hours.

"It's going to be a great show," said Bill Cooke of NASA's Meteoroid Environment Office at the Marshall Space Flight Center in Alabama.

History of fiery tears

August is also known as the month of "The Tears of St. Lawrence."

Laurentius, a Christian deacon, is said to have been martyred by the Romans in 258 AD on an iron outdoor stove. It was in the midst of this torture that Laurentius cried out:

"I am already roasted on one side and, if thou wouldst have me well cooked, it is time to turn me on the other."

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The Saint's death was commemorated on his feast day, Aug. 10. King Phillip II of Spain built his monastery place, the "Escorial," on the plan of the holy gridiron.

And the abundance of shooting stars seen annually between approximately Aug. 8 and 14 have come to be known as St. Lawrence's "fiery tears."

The reality

We know today that these meteors are actually the dusty remains left behind by the comet Swift-Tuttle.

Discovered back in 1862, and most recently observed in 1992, this comet takes approximately 130 years to circle the Sun. And in much the same way that the Tempel-Tuttle comet leaves a trail of debris along its orbit to produce the Leonid Meteors of November, Comet Swift-Tuttle produces a similar debris trail along its orbit to cause the Perseids.

Indeed, every year during mid-August, when the Earth passes close to the orbit of Swift-Tuttle, the material left behind by the comet from its previous visits rams into our atmosphere at approximately 37 miles per second (60 kps) and creates bright streaks of light in our midsummer night skies.

Perfect prospects

According to the best estimates, in 2007 the Earth is predicted to cut through the densest part of the Perseid stream sometime around 2 a.m. ET on Monday, Aug. 13. That corresponds to 11 p.m. PT on Aug. 12 for those living in the Western United States or Canada.

The interval when the meteors will be falling at their highest rates will likely last several hours or more on either side of these times.

As a result, it is the late-night hours Sunday, on through the first light of dawn Monday that holds the greatest promise of seeing a very fine Perseid display.

The moon, whose bright light almost totally wrecked last year's shower, will have zero impact this year. The moon will be new on Sunday, meaning that there will be no interference from it at all.

Perfect!

What to expect

A very good shower will produce about one meteor per minute for a given observer under a dark country sky. Any light pollution or moonlight considerably reduces the count.

The August Perseids are among the strongest of the readily observed annual meteor showers, and at maximum activity nominally yields 90 or 100 meteors per hour.

However, observers with exceptional skies often record even larger numbers.

Typically during an overnight watch, the Perseids are capable of producing a number of bright, flaring and fragmenting meteors, which leave fine trains in their wake.

On the night of shower maximum, the Perseid radiant is not far from the famous "Double Star Cluster" of Perseus (hence the name, "Perseid").

Low in the northeast during the early evening, it rises higher in the sky until morning twilight ends observing.

Shower members appearing close to the radiant have foreshortened tracks; those appearing farther away are often brighter, have longer tracks, and move faster across the sky.

About five to 10 of the meteors seen in any given hour will not fit this geometric pattern, and may be classified as sporadic or as members of some other (minor) shower.

Plan your time

Making a meteor count is as simple as lying in a lawn chair or on the ground and marking on a clipboard whenever a "shooting star" is seen.

Watching for the Perseids consists of lying back, gazing up into the stars, and waiting.

It is customary to watch the point halfway between the radiant (which will be rising in the northeast sky) and the zenith, though it's perfectly all right for your gaze to wander.

Counts should be made on several nights before and after the predicted maximum, so the behavior of the shower away from its peak can be determined.

Usually, good numbers of meteors should be seen on the preceding and following nights as well. The shower is generally at one-quarter strength one or two nights before and after maximum.

A few Perseids can be seen as much as two weeks before and a week after the peak.

The extreme limits, in fact, are said to extend from July 17 to August 24, though an occasional one may be seen almost anytime during the month of August.

In addition to the Perseids, some skywatchers will have an opportunity to view another potentially strong meteor display at the beginning of September: the Aurigid meteors. We'll have more details on this in next week's Night Sky, so stay tuned!

August Meteor Showers Provide Treat for Skygazers

Mon, 06 Aug 2007 14:13:56 -0400

For Northern Hemisphere skywatchers, August is usually regarded as "meteor month," with one of the best displays of the year reaching its peak near mid-month.

That display is, of course, the annual Perseid meteor shower beloved by everyone from meteor enthusiasts to summer campers.

This year experts predict an excellent Perseids display, as peak activity will coincide with a new moon, meaning dark skies that allow the meteors to shine.

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Meanwhile, there are other lesser-known summer meteor displays to check out right now.

When to watch

In general, the Earth encounters richer meteoric activity during the second half of the year. And you're more likely to see twice as many meteors per hour in the predawn hours as compared to the evening hours.

Here's why: During the pre-midnight hours, we are on the trailing side of the Earth as it moves through space. Any meteoric particle generally must have an orbital velocity greater than that of the Earth to "catch" us.

After midnight, when we have rotated onto the Earth's leading side, any particle that lies along the planet's orbital path will enter our atmosphere as a meteor.

In these head-on collisions, meteors hit our atmosphere at speeds of 7 to 45 miles per second. Their energy of motion rapidly dissipates in the form of heat, light and ionization, creating short-lived streaks of light popularly referred to as "shooting stars."

Summertime meteors are especially noticeable between mid-July and the third week of August. Between Aug. 3 and 15, there are six different minor displays. When they run (and peak):

— Southern Delta Aquarids, July 12-Aug. 19 (July 28), 15 per hour, faint, medium speed.

— Alpha Capricornid, July 3-Aug. 15 (July 30), 4-5 per hour, slow, bright, a few fireballs.

— Southern Iota Aquarids, July 25-Aug. 15 (Aug. 4), 1 to 2 per hour, faint, medium speed.

— Northern Delta Aquarids, July 15-Aug. 25 (Aug. 8), 1 to 4 per hour, faint, medium speed.

— Kappa Cygnids, Aug. 3-Aug. 25 (Aug. 18), 1 to 3 per hour, slow moving, sometimes brilliant.

— Northern Iota Aquarids, Aug. 11-31 (Aug. 20), 1 to 3 per hour, faint, medium speed.

How to watch

The only equipment you'll need is your eyes and a modest amount of patience. Telescopes and binoculars are of no use for fast-moving meteors.

The actual number of meteors a single observer can see in an hour depends strongly on sky conditions.

The rates above are based on a limited star magnitude of +6.5 (a really good sky), an experienced observer and an assumption that the radiant is directly overhead.

The radiant is the place in the sky where the paths of shower members, if extended backward, would intersect when plotted on a star chart.

Your clinched fist held at arm's length is equal to roughly 10 degrees on the sky.

So if the radiant is 30 degrees ("three-fists") above the horizon, the hourly rate is halved; at 15 degrees it is a third.

While the hourly rates from these other meteor streams are but a fraction of the numbers produced by the Perseids, combined overall they provide a wide variety of meteors of differing colors, speeds and trajectories.

The Southern Delta Aquarids, for example, can produce faint, medium speed meteors. The Alpha Capricornids generate slow, bright, long trailed yellowish meteors. And the Kappa Cygnids are classified as slow-moving and sometimes producing brilliant flaring fireballs.

Note that five of the six showers listed come from the region around the constellations of Aquarius and Capricornus. These constellations are highest in the southern sky between roughly 1 and 3 a.m. local daylight time, so that's generally the best time to watch.

And don't forget to reserve the overnight hours of Aug. 12-13 for observing the Perseids, which under clear, dark skies will produce one or two meteors every minute.

How to See Tuesday Morning's Lunar Eclipse

Fri, 24 Aug 2007 13:53:44 -0400

Tuesday morning, Aug. 28, brings us the second total lunar eclipse of 2007. Those living in the Western Hemisphere and eastern Asia will be able to partake in at least some of this sky show.

The very best viewing region for viewing this eclipse will fall across the Pacific Rim, including the western coasts of the United States and Canada, as well as Alaska, Hawaii, New Zealand and eastern Australia.

All these places will be able to see the complete eclipse from start to finish.

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Europeans will miss out on the entire show, as the Moon will be below the horizon during their mid and late morning hours.

What to look for

The eclipse will begin when the Moon enters the faint outer portion, or penumbra, of the Earth's shadow about an hour before it begins moving into the umbra.

The penumbra, however, is all but invisible to the eye until the Moon becomes deeply immersed in it. Look for a slight hint of shading or smudginess on the eastern (left) edge of the lunar disk about 40 minutes after the Moon first enters the penumbral shadow.

The most obvious part of the eclipse will be when the Moon is passing through the dark umbral shadow of the Earth.

On this occasion, the full Moon will track just to the south of the center of the Earth's umbra, a deep path almost through the center of the umbra, which will result in a total phase lasting an unusually long 1 hour and 30 minutes (the maximum possible is 1 hour and 47 minutes).

Because some of the sunlight striking our planet is diffused and scattered by our atmosphere, the Earth's shadow is not entirely dark. Enough of this light reaches the Moon to give it a faint orange or reddish glow even when it's totally eclipsed.

At greatest eclipse, the Moon's southern limb will pass 1,039 miles (1,672 kilometers) from the outer edge of the dark shadow.

This should produce a relatively dark eclipse, with the Moon glowing a dull coppery color along its lower portion and a deep brown or gray over its upper portion.

SPACE.com encourages viewers to estimate the Danjon value — a five-point scale of lunar luminosity ("L") to classify eclipses — at mid-totality.

Timetable

The beginning and ending of a lunar eclipse happens simultaneously for every viewer, unlike an eclipse of the Sun. Hence the simple schedule below holds for all places:

Where you can see it

As for the region of visibility for this eclipse, it pretty much is the "flip side" of the last eclipse, in March.

Whereas Africa, Europe and western Asia had ringside seats for that late-winter spectacle, this time they are completely out of luck.

The timing of the eclipse comes during their late morning and early afternoon hours, with the eclipsed Moon below the horizon.

Conversely, almost the entire Pacific Ocean is turned toward the Moon during this August eclipse.

In fact, at mid-totality the Moon will appear directly overhead a spot over the open waters of the Pacific, roughly 1,800 mi. (2,900 km.) south of Hawaii.

And whereas for the March lunar eclipse those near and along the Pacific Rim could catch a brief view at dawn, while the Americas view coincided with moonrise, in August we are presented with the converse of these circumstances.

The eclipse will already be underway at moonrise for Japan and much of Australia on the evening of Aug. 28.

The rest of eastern Asia will either have the Moon rise during totality, or will see it as it is exiting the Earth's shadow.

But from North America, the eclipse occurs during the early morning hours of Aug. 28.

The Canadian Maritimes will miss totality, as the Moon will set in partial eclipse before it begins.

Across the eastern third of the United States, moonset arrives in the midst of the total phase. So, less than six months after easterners watched the Moon rise during totality, now comes the opportunity to be treated to the sight of the Moon setting during totality!

However, thanks to advancing morning twilight, plus horizon haze, for those living in the Northeastern and Middle Atlantic States it is likely that the dim Moon (some 10,000 times fainter than a normal full Moon) will more-or-less vanish from view near or just after the onset of totality.

Over the central states, the Moon will set in partial eclipse, while emerging from the umbra; the farther west, the less of the Moon will be so covered.

An interesting observation for watchers in this zone who have an unobstructed eastern and western horizon is to attempt seeing the partially eclipsed setting Moon and the rising Sun at the same time. The Moon will remain above the horizon for a few minutes after sunup.

From the western states, all umbral stages will be visible before moonset affording the best views of totality (in a dark sky) within the contiguous states and more than making up for being completely shut out of last March's eclipse.

Alaska and Hawaii will see the eclipse happen in the middle of their night. Mid-totality for Anchorage comes at 1:37 a.m. Alaskan Daylight Time and for Honolulu at 12:37 a.m. Hawaii Standard Time.

Coming attraction

Should clouds interfere with your attempt to view Tuesday's eclipse, you won't have very long to wait for the next opportunity. That will come just under six months from now, on the night of Feb. 20-21.

Another total lunar eclipse (the third in less than a year's time) will be visible throughout much of North and South America as well as Europe, Africa and parts of western Asia.

The Moon and Saturn Get Together, at Least From Earth

Fri, 02 Feb 2007 16:44:46 -0500

Watching the full Moon rise over the east-northeast horizon on Friday evening, Feb. 2, you will probably notice a rather bright yellowish-white "star" shining sedately just above and to the Moon's right.

That object is not a star, however, but the planet Saturn.

Currently, Saturn is at its best for 2007. It can be found to the west (right) of the famous "Sickle" of Leo — a backwards question mark-shaped star pattern, which contains Leo's brightest star, Regulus, at the Sickle's base.

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On Feb. 10, Saturn will be at opposition to the Sun, meaning it will be rising at sunset, reaches its highest point in the southern sky at midnight then drops down below the west-northwest horizon at sunrise. In other words, it's now available for viewing all night long.

Galileo's footsteps

Saturn is the telescopic showpiece of the night sky, thanks to its great ring system in all of their icy, glimmering elegance.

In small telescopes, they surprise even veteran observers with their chilling beauty even though it is expected.

Certainly they will delight anyone this winter who received a telescope as a holiday gift. Any telescope magnifying more than 30-power will show them.

Galileo Galilei (1564-1642) was the first to view the rings in 1610, although what he saw through his crude telescope left him completely baffled; his crude, imperfect "optick tube" revealed Saturn as having an odd pair of appendages or companion bodies on either side.

He couldn't make them out clearly and thought that Saturn was a triple body, two small orbs on either side of a large one.

Galileo announced this discovery in 1610 with an anagram written in Latin.

The jumbled letters could be transposed to read: Altissimum planetam tergeminum observavi ("I have observed the highest planet to be triple.") Later, when the rings turned edgewise to Earth and the two companions disappeared, Galileo invoked an ancient myth when he wrote, "Has Saturn swallowed his children?"

Galileo lamented that his mind was too weak to comprehend this strange phenomenon.

Actually, it was his telescope that was too weak; a better telescope would have revealed Saturn's companions as rings.

It wasn't until nearly a half-century later that telescope lenses improved to the point where the ringlike nature of these "appendages" became apparent.

On March 25, 1655, a young Dutch mathematician, Christian Huygens (1629-1695) utilized a much better telescope, and on March 25, 1655 saw the rings for what they really were.

Today, we know they are composed of a myriad of small solid particles and are likely the icy fragments of a satellite that probably ventured too close to Saturn and was torn apart by tidal forces.

Slow orbit

The ancients regarded Saturn as the "highest" planet, occupying the outermost or highest sphere before that of the fixed stars.

Since Saturn requires 29.5 years to orbit the Sun, its progress through the zodiacal constellations is quite slow, averaging about 2.5 years per constellation. The last time this planet was located in Leo was in 1979.

In mythology, Saturn closely resembled the Greek god Cronus, but he's more usually recognized as the Roman god of agriculture.

The name is related to both the noun satus (seed corn) and the verb serere (to sow).

But why would the planet Saturn be linked to agriculture? Perhaps a clue can be found from the ancient Assyrians, who referred to Saturn as lubadsagush, which translated, meant "oldest of the old sheep."

Possibly this name was applied because Saturn seems to move so very slowly among the stars; it may have also reminded sky watchers of the slow gait of plowing oxen or cattle.

Newly Visible Comet Brightens Northern Skies

Mon, 05 Nov 2007 11:09:04 -0500

Skywatchers throughout the Northern Hemisphere report the newly visible Comet Holmes is a remarkable sight even under city lights.

The comet, described in glowing terms by many observers, should continue to be visible to the naked eye for at least the next few weeks.

Only a couple comets each decade are this easy to see.

Holmes is actually an old comet. First seen in November 1892 by British observer Edwin Holmes, it has since made 16 circuits around the Sun and should have fizzled out a long time ago.

It made its closest approach to the Sun last May, yet never came closer to it than 191 million miles (307 million kilometers).

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The comet is actually moving away from the Sun now, almost midway between the orbits of Mars and Jupiter. Not exactly a recipe for an outbust, since solar heating is typically what triggers comets to brighten.

But sometime on Oct. 23, this comet underwent an explosive outburst and within just 24 hours increased its brightness almost a million-fold.

Since then, Holmes has been putting on a unique display, looking very different than any other comet of our generation: It has yet to sprout a noticeable tail, while its head — called the coma — appears like a round, yellowish fuzz ball in the constellation Perseus, and is visible for most of the night.

Since its outburst, Holmes has shone almost consistently between magnitudes 2 and 3, making it similar in brightness to the stars that make up the famous Big Dipper. (On this astronomer's scale, smaller numbers represent brighter objects.)

Use the 'W' as a guide

You can find Comet Holmes by using the "W" of Cassiopeia as your guide. The five stars in a conspicuous zigzag pattern are high in the northeast sky during the mid-evening hours.

Draw an imaginary line from the star Gamma Cass down to Delta Cass (known also as Ruchbah).

Extend the line downward about five times the distance between these two stars and you'll come very close to where Comet Holmes is.

The comet itself forms a triangle with Alpha Persei (known also as "Mirfak") and Delta Persei.

If you have binoculars, you'll know the comet immediately when you see it: a small, albeit distinct, circular lemon-yellow cloud of light. A small telescope will help bring out the fuzzy details.

The moon, which was full on Oct. 26 and whose brilliant light hindered comet viewing to a degree, is now diminishing in phase and rising later in the night, allowing viewers an increasing window of dark sky before the moon interferes.

By Nov. 4, it was rising around 1:20 a.m. (standard time), having shrunk to a crescent, and leaving more than half of the night dark for comet watchers.

Reports from around the world

Long Island, N.Y. amateur, Bryan Bradley writes: "I went out the past two nights and observed the comet from my driveway observatory. Very interesting how bright it has become. My daughters also saw it with me and commented that it looked like a big fuzzy ball, but where is the tail?"

Percy Mui photographed the comet from Illinois, capturing the fuzzball appearance reported by many.

Another Long Island amateur observer, Rich Tyson, relates that "My wife Antoinette described Comet Holmes as looking like a 'fried egg.' Can we call it the 'Fried Egg Comet?'"

Well-known comet observer John Bortle, of Stormville, N.Y., has carefully scrutinized the comet on a number of nights with a variety of different instruments.

He saw the comet on the evening of Oct. 28 without the glaring Moon in the sky. "So much info was recorded I can't begin to report more than a fragment of it here. A double envelope feature surrounding the comet is truly spectacular in the darker sky."

Similar raves were coming in from other places around the globe.

Eddie Guscott from Essex, England had been trying to see Comet Holmes since it exploded into view, but "the weather here has been dire: 100-percent cloud. So it was a great surprise to finally get an hour of clear weather enabling me to observe this wonderful sight. I have never seen anything like it before."

Robert McNaught, discoverer earlier this year of a spectacular daylight comet that bears his name, observed Comet Holmes from Siding Spring, Australia.

"The comet was a surprisingly easy naked eye object despite the near-full moon sitting above it," McNaught said of comet Holmes. "Lovely views in the Uppsala's 6-inch finderscope at 80x showing the faint stellar condensation and 'an' within the large 'planetary nebula'-like coma. Very impressive."

Also during the night of Oct. 28, there was a brief flurry of excitement as many observers thought they had seen the comet's nucleus split in two.

What had actually happened, however, was that the comet passed very near to a faint background star that had virtually the same brightness as the inner coma, giving the impression that a splitting had occurred. But as of this writing, the entire comet remains intact.

What caused the outburst?

More than a week after Comet Holmes erupted, astronomers are still debating what caused it.

Some think it might be due to a rich vein of volatile ices on the comet's nucleus that was suddenly exposed to sunlight. This is actually the second time that Holmes has flared up in this manner, the last time coming in its discovery year of 1892.

Bortle suggested the nucleus of Comet Holmes might consist of low-density material that, over time and through outgassing, develops a large region with a very tenuous structure, perhaps honeycomb-like.

"Cometary nuclei being irregular in shape, rotation or perhaps even the minute gravity of the nucleus itself will create increasing shear forces if the area is remote from the center of rotation," Bortle said. "At some point, the highly fragile bonds connecting the honeycomb of material will reach the failing point and a collapse, or more likely a sudden crushing/consolidating event on a grand scale perhaps covering several square kilometers wide and deep, will occur. This crushing collapse would expel a truly gigantic volume of dust in the process."

Another outburst possible?

The show could have a reprise later this year.

"Those who are familiar with terrestrial structural collapse situations are aware that the primary event often leaves a large amount of instability in the material involved," Bortle said. "This remaining instability will only remain for a short time before a further adjustment toward stability occurs, resulting in a major second collapse, with an outward physical appearance very similar to that of the initial event."

Back in 1892, Comet Holmes underwent a second outburst about 75 days after the first.

Will there be a "cosmic aftershock" that will again cause the comet's brightness to again spike a similar number of days after the big Oct. 23 outburst this year? Bortle thinks it's a possibility.

"I would urge everyone to watch very carefully for a possible repeat of this secondary event about the turn of the year," he said.

Leonid Meteor Shower Peaks This Weekend

Mon, 19 Nov 2007 07:56:35 -0500

This weekend brings us the return of the famous Leonid Meteor Shower, a meteor display that in recent years has brought great anticipation and excitement to skywatchers around the world.

While the Leonids have been spectacular in years past, this year a modest display is expected.

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Solely from the standpoint of viewing circumstances, this will be a favorable year to look for these meteors, since the Moon will be at first quarter phase and will have set in the West long before the constellation Leo (from which the meteors get their name) has climbed high in the sky.

What they are

The Leonid meteors are debris shed into space by the Tempel-Tuttle comet, which swings through the inner solar system at intervals of 33.25 years.

With each visit the comet leaves behind a trail of dust in its wake.

Lots of the comet's old dusty trails litter the mid-November part of Earth's orbit and the Earth glides through this debris zone every year.

Occasionally we'll pass directly through an unusually concentrated dust trail, or filament, which can spark a meteor storm resulting in thousands of meteors per hour.

That's what happened in 1999, 2001 and 2002, because Tempel-Tuttle had gone through the inner solar system in 1998.

But now, the comet — and its dense trails of dust — have all receded far beyond Earth's orbit and back into the outer regions of the solar system. So this year there there is little if any chance of heightened activity.

Peak activity

In the 2007 Observer's Handbook of the Royal Astronomical Society of Canada, meteor experts Margaret Campbell-Brown and Peter Brown indicate that this year's peak activity should occur on the night of Nov. 17-18.

They cite 4:00 GMT on Nov. 18, which corresponds to 11 p.m. EST and 8 p.m. PST on the evening of Nov. 17.

This is the moment when the Earth will be passing closest to the orbit of the long-departed comet, and when our planet seemingly is most likely to encounter some residual comet material.

This time is highly favorable for those in Europe and Africa. But for North American observers, Leo will still be below the horizon; they will have to wait until later in the night to catch a view of the Leonids.

While Leonid rates are unpredictable, it is unlikely that more than about 15 meteors per hour will be seen this year.

Other meteor researchers concur that Leonid activity will be modest at best.

In the 2007 Astronomical Calendar, British meteor astronomer Alastair McBeath also cites the night of Nov. 17-18 as the best night for Leonid viewing: "This year may see a return to more typical meteor numbers, perhaps 15+?"

McBeath gives 3:00 GMT on Nov. 18 for this year's Leonid peak and states that observing conditions "should be impressive for covering this likely maximum, especially from Europe, North Africa and the Near East."

Possible brief outburst over Asia?

Other meteor researchers, however, such as NASA's Peter Jenniskens, Jeremie Vaubaillon of France, Esko Lyytinen of Finland, David Asher of Ireland and Mikhail Maslov of Russia have examined Leonid prospects for this year and also suggest watching for some meteor activity also on Nov. 18, but much later in the day.

For instance: sometime between 22:36 and 23:03 GMT, the Earth might interact with material that was shed by comet Tempel-Tuttle back in the year 1932.

But even in this case, the intensity of the shower will fall far short of the memorable Leonid displays that occurred as we transitioned from the 20th to the 21st century.

"Unfortunately it isn't possible to have a 'once in a lifetime' chance every year," Asher notes.

It is possible the dusty material from 1932 will create a brief bevy of 30 to 60 Leonids per hour. But the time frame when these meteors are predicted to be most numerous only favors observers in central and eastern Asia (where it will be the early morning hours of November 19).

And unfortunately, for Japan and Australia, the sun will have already risen!

How to watch

The meteors will appear to emanate from out of the so-called "Sickle" of Leo. Prospective viewers should not concentrate on that area of the sky around Leo, but rather keep their eyes moving around to different parts of the sky.

Because Leo does not start coming fully into view until the after midnight hours, that would be the best time to concentrate on looking for the Leonid meteors.

The hours after midnight are generally best for watching for "shooting stars" anyway, because before midnight we are riding on the back side of the Earth in its orbit around the sun, whereas after midnight we are on the front or advancing side.

After midnight the only meteoroids escaping collision are those ahead of the Earth and moving in the same direction with velocities exceeding 18.5 miles (29.8 kilometers) per second. All others we will either overtake or meet head-on.

But before midnight, when we are on the backside, the only meteoroids we encounter are those with velocities high enough to overtake the Earth.

Therefore, on the average, morning meteors appear brighter and faster than those we see in the evening.

And because the Leonids are moving along in their orbit around the sun in a direction opposite to that of Earth, they slam into our atmosphere nearly head-on, resulting in the fastest meteor velocities possible: 45 miles (72 kilometers) per second.

Such speeds tend to produce bright meteors, which leave long-lasting streaks or trains in their wake.

New Green Comet Set for April Show

Mon, 02 Apr 2007 03:14:12 -0400

A new comet has recently been discovered, and like the brilliant Comet McNaught from earlier this year, this latest discovery belongs to an Australian: Comet Lovejoy (C/2007 E2).

On March 15, Terry Lovejoy of Thornlands, Queensland, Australia, discovered a 9th-magnitude comet in the southern constellation Indus the Indian. In reporting the find to the Central Bureau for Astronomical Telegrams (CBAT), in Cambridge, Mass., Lovejoy described the comet as having a coma that appeared distinctly green in color, with a slight extension to the southwest.

Remarkably, Lovejoy made the discovery not with a telescope but using an off-the-shelf digital camera! In fact, it appears to be the very first case of the discovery of a comet discovered in this manner.

Lovejoy was using a Canon 350D with a zoom lens set to 200-mm focal length at f/2.8. Lovejoy spotted the object near the frame edge in 16 exposures of 90 seconds each. The images were obtained during a comet-hunting survey that Lovejoy has been conducting for more than two years.

The first independent confirmation was obtained by John Drummond (Possum Observatory, Gisborne, New Zealand) on March 16. He used a 41-cm reflector and visually estimated the magnitude as 9.5 — about 15 times dimmer than the faintest sky objects that can be seen without optical aid. Drummond estimated the coma diameter as 2.6 arc minutes (roughly equal to about 1/12 that of the apparent width of the Moon).

The green comet is too dim to see with the naked eye, but it’s a nice target for backyard telescopes. The first official orbit was calculated by Brian G. Marsden of the CBAT on March 19. He took 36 precise positions spanning a three day interval and determined the comet's perihelion date (when it will sweep closest to the Sun — a distance of 101.3 million mi/163 million km.) as March 27. The comet's distinctive greenish hue seems to suggest that it is rich in cyanogens and diatomic carbon.

Unlike Comet McNaught, which took a southerly route after passing the Sun, Comet Lovejoy will be progressing north during April and will soon become favorably placed for observation for observers in the Northern Hemisphere. Also unlike Comet McNaught, Comet Lovejoy will (unfortunately) not become a naked-eye object; it probably will get no brighter than magnitude +7.5. That's still about two and a half times fainter than the faintest naked-eye star. But it still should continue to be an interesting object to follow with binoculars and small telescopes as it moves north during April.

For most northern observers, it will not be until the second week of April that Comet Lovejoy will emerge from out of the dawn twilight and be positioned low in the southeast sky.

It will be located between the constellations of Capricornus the Sea Goat and Sagittarius the Archer [sky map]. During April 20-25, the comet will appear to cross the Milky Way while passing through the southern half of Aquila the Eagle. This is also about the time when it will be passing closest to Earth (41 million mi/66 million km, Apr. 24-26) and should appear at its brightest. Toward month's end, it will glide between Lyra the Lyre and Hercules, and appearing to pass almost directly overhead at around 3 a.m. local daylight time.

On Comets ml — an Internet forum dedicated to the discussion of comets — Terry Lovejoy posted his thoughts after he made his discovery: "After a very intense search effort in 2006 without success, I had wound back my efforts in 2007 (partly because of fatigue!). March 15 was only the second time this year I had done any searches in the morning sky. All told I estimate I have examined about 1000 image fields since late 2004, which would equate to about 1000 hours. 2007 has been a good year with two lifetime astronomy goals finally achieved. The first goal was to see a daylight comet (McNaught) and the second to discover a comet."

"Mission accomplished!"

Bits of Halley's Comet to Rain Down Sunday Morning

Fri, 19 Oct 2007 21:03:59 -0400

A junior version of the famous Perseid meteor shower is scheduled to reach its maximum before sunrise on Sunday morning, Oct. 21.

This meteor display is known as the Orionids because the meteors seem to fan out from a region to the north of Orion's second brightest star, ruddy Betelgeuse.

Weather permitting and under very dark skies away from light pollution, skywatchers could see several meteors per hour. Rates will be significantly lower in cities and suburban areas.

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Interestingly, this year, brilliant Mars is nearby and the apparent source of these meteors, called the radiant, will be positioned roughly between Mars and Betelgeuse.

When and where to watch

Currently, Orion appears ahead of us in our journey around the Sun, and has not completely risen above the eastern horizon until after 11:00 p.m. local daylight time.

Expect to see few, if any Orionids before midnight — especially this year, with a bright waxing gibbous Moon glaring high in the western sky.

But moonset is around 1:30 a.m. local daylight time on Sunday, and that's a good time to begin preparing for your meteor vigil.

At its best several hours later, at around 5:00 a.m. when Orion is highest in the sky toward the south, Orionids typically produce around 20 to 25 meteors per hour under a clear, dark sky.

"Orionid meteors are normally dim and not well seen from urban locations," said meteor expert Robert Lunsford, adding, ". . . it is highly suggested that you find a safe rural location to see the best Orionid activity."

According to Lunsford, Orionid activity has been increasing noticeably since Oct. 17 when they were appearing at roughly five per hour in dark-sky conditions.

After peaking on Sunday morning, activity will begin to slowly descend, dropping back to around five per hour around Oct. 26. The last stragglers usually appear sometime in early to mid Nov.

Halley's Legacy

In studying the orbits of many meteor swarms, astronomers have found that they correspond closely to the orbits of known comets.

The Orionids are thought to result from the orbit of Halley's Comet; some of the dust which has shaken loose from this famous object as it runs its gigantic loop from the Sun out to Neptune, ram our atmosphere to create the effect of these "shooting stars."

There are actually two points along Halley's path where it comes relatively near to our orbit.

One of these points corresponds to early May and causes a meteor display that emanates from the constellation Aquarius, the Water Carrier.

The other point lies near the late October part of our orbit and produces the Orionids.

In May we meet the "river of rubble" shed by the comet on their way outward from their nearest approach to the Sun, while in October we encounter the part of the meteor stream moving inward toward the Sun.

The meteors are moving through space opposite or contrary to our orbital direction of motion.

That explains why both the Aquarids and the Orionids hit our atmosphere very swiftly at 41 miles (66 kilometers) per second — only the November Leonids move faster.

Another distinguishing characteristic that the October Orionids share with the May Aquarids is that they start burning up very high in our atmosphere, possibly because they are composed of lightweight material.

This means they likely come from Halley's diffuse surface and not its core.

What to expect

Last year, there was an unexpected surprise when the Orionids put on a display more worthy of the Perseids.

Observers saw meteors falling at double the normal rate, or 40 to 50 per hour. In addition, many Orionids were much brighter than normal; a few even rivaled Venus in brilliance.

Two meteor researchers, Mikaya Sato and Jun-ichi Watanabe of Japan's National Astronomical Observatory, recently announced in a paper released by the Astronomical Society of Japan that the unusual concentration of large particles that produced last years Orionids, were probably ejected from Halley's Comet almost 3,000 years ago and are being held together by interactions with Jupiter about every 71 years.

Apparently, there may also have been unusual Orionid activity during the years 1933 through 1938, so perhaps after an absence of seven decades this concentration of comet material has returned, implying another rich Orionid display might be in offing this year.

The only way to know is to step outside just before the break of dawn on the morning of Oct. 21 (try the mornings of Oct. 20 and 22 as well). Almost certainly, you should sight at least a few of these offspring of Halley's Comet as they streak across the sky.

How a Lunar Eclipse Saved Columbus

Fri, 08 Feb 2008 14:23:17 -0500

On the night of Feb. 20, the full moon will pass into Earth's shadow in an event that will be visible across all of the United States and Canada.

The total lunar eclipse will be made even more striking by the presence of the nearby planet Saturn and the bright bluish star, Regulus.

Eclipses in the distant past often terrified viewers who took them as evil omens. Certain lunar eclipses had an overwhelming effect on historic events. One of the most famous examples is the trick pulled by Christopher Columbus.

Shipwrecked

On Oct. 12, 1492, as every schoolchild has been taught, Columbus came ashore on an island northeast of Cuba. He later named it San Salvador (Holy Savior). Over the next ten years Columbus would make three more voyages to the "New World," which only bolstered his belief that he reached the Far East by sailing West.

It was on his fourth and final voyage, while exploring the coast of Central America that Columbus found himself in dire straits. He left Cádiz, Spain on May 11, 1502, with the ships Capitana, Gallega, Vizcaína and Santiago de Palos. Unfortunately, thanks to an epidemic of shipworms eating holes in the planking of his fleet, Columbus' was forced to abandon two of his ships and finally had to beach his last two caravels on the north coast of Jamaica on June 25, 1503.

Initially, the Jamaican natives welcomed the castaways, providing them with food and shelter, but as the days dragged into weeks, tensions mounted. Finally, after being stranded for more than six months, half of Columbus' crew mutinied, robbing and murdering some of the natives, who, themselves grew weary of supplying cassava, corn and fish in exchange for little tin whistles, trinkets, hawk's bells and other rubbishy goods.

With famine now threatening, Columbus formulated a desperate, albeit ingenious plan.

Almanac to the Rescue

Coming to the Admiral's rescue was Johannes Müller von Königsberg (1436-1476), known by his Latin pseudonym Regiomontanus. He was an important German mathematician, astronomer and astrologer.

Before his death, Regiomontanus published an almanac containing astronomical tables covering the years 1475-1506. Regiomontanus' almanac turned out to be of great value, for his tables provided detailed information about the sun, moon and planets, as well as the more important stars and constellations by which to navigate. After it was published, no sailor dared set out without a copy. With its help, explorers were able to leave their customary routes and venture out into the unknown seas in search of new frontiers.

Columbus, of course, had a copy of the Almanac with him when he was stranded on Jamaica. And he soon discovered from studying its tables that on the evening of Thursday, Feb. 29, 1504, a total eclipse of the moon would take place soon after the time of moonrise.

Armed with this knowledge, three days before the eclipse, Columbus asked for a meeting with the natives Cacique ("chief") and announced to him that his Christian god was angry with his people for no longer supplying Columbus and his men with food. Therefore, he was about to provide a clear sign of his displeasure: Three nights hence, he would all but obliterate the rising full moon, making it appear "inflamed with wrath," which would signify the evils that would soon be inflicted upon all of them.

Bad Moon Rising

On the appointed evening, as the Sun set in the West and the moon started emerging from beyond the eastern horizon, it was plainly obvious to all that something was terribly wrong. By the time the moon appeared in full view, its lower edge was missing!

And, just over an hour later, as full darkness descended, the moon indeed exhibited an eerily inflamed and "bloody" appearance: In place of the normally brilliant late winter full moon there now hung a dim red ball in the eastern sky.

According to Columbus' son, the natives were terrified at this sight and ". . . with great howling and lamentation came running from every direction to the ships laden with provisions, praying to the Admiral to intercede with his god on their behalf." They promised that they would gladly cooperate with Columbus and his men if only he would restore the moon back to its normal self. The great explorer told the natives that he would have to retire to confer privately with his god. He then shut himself in his cabin for about fifty minutes.

"His god" was a sandglass that Columbus turned every half hour to time the various stages of the eclipse, based on the calculations provided by Regiomontanus' almanac.

Just moments before the end of the total phase Columbus reappeared, announcing to the natives that his god had pardoned them and would now allow the moon to gradually return. And at that moment, true to Columbus' word, the moon slowly began to reappear and as it emerged from the Earth's shadow, the grateful natives hurried away. They then kept Columbus and his men well supplied and well fed until a relief caravel from Hispaniola finally arrived on June 29, 1504. Columbus and his men returned to Spain on Nov. 7.

Another Side to the Story

In an interesting postscript to this story, in 1889, Mark Twain, likely influenced by the eclipse trick, wrote the novel, "A Connecticut Yankee in King Arthur's Court." In it, his main character, Hank Morgan, used a gambit similar to Columbus'.

Morgan is about to be burned at the stake, so he "predicts" a solar eclipse he knows will occur, and in the process, claimed power over the sun. He gladly offers to return the sun to the sky in return for his freedom and a position as "perpetual minister and executive" to the king.

The only problem with this story is that on the date that Mark Twain quoted — June 21, 528 A.D. — no such eclipse took place. In fact, the moon was three days past full, a setup that can't generate an eclipse.

Perhaps he should have consulted an almanac!

Brief, Intense Meteor Shower Set for Thursday Night

Fri, 04 Jan 2008 07:32:11 -0500

The Quadrantid meteor shower is due to reach maximum in the predawn hours of Friday, Jan. 4. The Quadrantids are notoriously unpredictable, but if any year promises a fine display, this could be it.

Indeed, this may end up being the best meteor shower of 2008.

The Quadrantid (pronounced KWA-dran-tid) meteor shower provides one of the most intense annual meteor displays, with a brief, sharp maximum lasting but a few hours.

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The timing of peak activity favors Western Europe and eastern North America.

Weather permitting, skywatchers in rural locations could see one or two shooting stars every minute during the peak.

Annual challenge

Each year, many factors combine to make the peak of this display difficult to observe.

— Peak intensity is exceedingly sharp: meteor rates exceed one-half of their highest value for only about 8-hours (compared to two days for the August Perseids). This means that the stream of particles that produce this shower is a narrow one — apparently derived within the last 500 years from a small comet.

— As viewed from mid-northern latitudes, we have to get up before dawn to see the Quadrantids at their best. This is because the radiant — that part of the sky from where the meteors to emanate — is down low on the northern horizon until about midnight, rising slowly higher as the night progresses. The growing light of dawn ends meteor observing usually by around 7 a.m. So, if the "Quads" are to be seen at all, some part of that 8-hour active period must fall between 2 and 7 a.m.

— In one out of every three years, bright moonlight spoils the view.

— Over northern latitudes, early January often sees inclement/unsettled weather.

It is not surprising then, that the Quadrantids are not as well-known as some of the other annual meteor showers, but 2008 may prove to be an unusual exception.

Exception this year

According to the International Meteor Organization, maximum activity this year is expected on Friday 1:40 a.m. Eastern Standard Time.

For those in the eastern United States, the radiant will be about one-quarter of the way up in the east-northeast sky. The farther to the north and east you go, the higher in the sky the radiant will be. To the south and west the radiant will be lower and the meteors will be fewer.

From Western Europe, the radiant will soar high in the east as the peak arrives just as morning twilight intervenes.

Quadrantid meteors are described as bright and bluish with long silvery trains. Some years produce a mere handful, but for favorably placed observers, this could be a shower to remember; at greatest activity, Quadrantid rates will likely range from 30 to 60 per hour for eastern parts of the U.S. and Canada, to 60 to 120 per hour for Western Europe.

Across central and western parts of North America, the shower's sharp peak will have already passed and meteor activity will be rapidly diminishing by the time the radiant has a chance to get very high in the northeastern sky. Nonetheless, hourly rates of perhaps 15 to 30 may still be seen.

The moon will be a waning crescent, not rising until after 4 a.m. and will add very little light to the sky.

History and mystery

Adolphe Quetelet of Brussels Observatory discovered the shower in the 1830's, and shortly afterward it was noted by several other astronomers in Europe and America.

The meteors are named after the obsolete constellation Quadrans Muralis, the Mural or Wall Quadrant (an astronomical instrument), depicted in some 19th-century star atlases roughly midway between the end of the Handle of the Big Dipper and the quadrilateral of stars marking the head of the constellation Draco. (The International Astronomical Union phased out Quadrans Muralis in 1922.)

Meteor showers are generally caused by debris from comets. Most of the "shooting stars" result from bits the size of sand grains, which vaporize as they streak through Earth's atmosphere.

The parentage of the Quadrantids was long a mystery, however.

Then Peter Jenniskens, an astronomer at the SETI Institute in Mountain View, Calif., noticed that the orbit of 2003 EH1 — a small asteroid discovered in March 2003 — ''falls snug in the shower.''

He believes that this 1.2-mile-wide (2 kilometers) chunk of rock is the source of the Quadrantids; possibly this asteroid is the burnt out core of the lost comet C/1490 Y1.

Western U.S. to Have Best Glimpse of Next Week's Perseid Meteor Shower

Fri, 08 Aug 2008 13:43:29 -0400

Every August, just when many people go vacationing in the country, where skies are dark, the best-known meteor shower makes its appearance.

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It is also the month of "The Tears of St. Lawrence," more commonly known as the Perseid Meteor Shower.

Laurentius, a Christian deacon, is said to have been martyred by the Romans in 258 AD on an iron outdoor stove. It was in the midst of this torture that Laurentius cried out:

"I am already roasted on one side and, if thou wouldst have me well-cooked, it is time to turn me on the other."

The saint's death was commemorated on his feast day, Aug. 10. King Phillip II of Spain built his monastery place, the "Escorial," on the plan of the holy gridiron. And the abundance of shooting stars seen annually between approximately Aug. 8 and Aug. 14 have come to be known as St. Lawrence's "fiery tears."

Viewing Prospects

In 2008, the Perseids are expected to reach their maximum on Aug. 12.

The exact time of maximum should be about 7 a.m. EDT on Aug. 12, according to Margaret Campbell-Brown and Peter Brown in the 2008 Observer's Handbook of the Royal Astronomical Society of Canada.

If so, the timing is very good for meteor watchers observing before dawn in North America, especially in the western states. And that morning, the waxing gibbous moon sets around 1:30 a.m. local daylight-saving time, leaving a dark sky for the next 3 hours.

Take full advantage of that moonless period. Next year, a last-quarter moon will illuminate the after-midnight sky with its light and will hinder observation of the Perseids.

Comet Bits

We know that these meteors actually are the dross of the Swift-Tuttle comet. Discovered in 1862, this comet takes approximately 130 years to circle the sun. In much the same way that the Tempel-Tuttle comet leaves a trail of debris along its orbit to produce the Leonid meteors of November, comet Swift-Tuttle produces a similar debris trail along its orbit to cause the Perseids.

Indeed, every year during mid-August, when the Earth passes close to the orbit of Swift-Tuttle, the material left behind by the comet from its previous visits rams into our atmosphere at approximately 37 miles per second and creates bright streaks of light in our midsummer night skies.

Comet Swift-Tuttle made its most recent appearance 16 years ago, in December 1992. For several years before and after its 1992 return, the Perseids were a far more prolific shower, appearing to produce brief outbursts of as many as several hundred meteors per hour, many of which were dazzlingly bright and spectacular.

The most likely reason was that the Perseids parent comet was, itself, passing through the inner solar system and that the streams of Perseid meteoroids in the comet's vicinity were larger and more thickly clumped together — hence, the reason for the brighter meteors and much-higher-than-normal meteor rates.

But with the comet now far back out in space, Perseid activity has pretty much returned to normal.

Meteor Clumps

A very good shower will produce about one meteor per minute for a given observer under a dark country sky. Any light pollution or moonlight considerably reduces the count.

The August Perseids are among the strongest of the readily observed annual meteor showers, and at maximum activity nominally yield 50 or 60 meteors per hour; however, observers with a wide-open view of exceptionally dark skies often record even larger numbers on the order of 90 or even 100 per hour.

But while 60 meteors per hour correspond to one meteor sighting every minute, keep in mind that this is only a statistical average. In reality, what usually is seen is what some have called "the clumping effect." Sometimes you'll see two or even three Perseids streak across the sky in quick succession, all within less than minute.

This is usually followed by a lull of several minutes or more, before the sky suddenly bears fruit once again.

When and Where to Look

Typically during an overnight watch, the Perseids are capable of producing a number of bright, flaring and fragmenting meteors, which leave fine trains in their wake.

On the night of shower maximum, the Perseid radiant is not far from the famous "Double Star Cluster" of Perseus. Low in the northeast during the early evening, it rises higher in the sky until morning twilight ends observing.

Shower members appearing close to the radiant have foreshortened tracks; those appearing farther away are often brighter, have longer tracks and move faster across the sky. About five to 10 of the meteors seen in any given hour will not fit this geometric pattern and may be classified as sporadic or as members of some other (minor) shower.

Watching for the Perseids consists of lying back, gazing up into the stars and waiting.

Perseid activity increases sharply in the hours after midnight, so plan your observing times accordingly. We are then looking more nearly face-on into the direction of the Earth's motion as it orbits the Sun, and the radiant is also higher up. Making a meteor count is as simple as lying in a lawn chair or on the ground and marking on a clipboard whenever a "shooting star" is seen.

Counts should be made on several nights before and after the predicted maximum, so the behavior of the shower away from its peak can be determined. Usually, good numbers of meteors should be seen on the preceding and following nights as well. The shower is generally at one-quarter strength one or two nights before and after maximum.

A few Perseids can be seen as early as two weeks before and a week after the peak. The extreme limits, in fact, are said to extend from July 17 to Aug. 24, though an occasional one might be seen almost anytime during the month of August.

How to Watch This Week's Leonid Meteor Shower

Fri, 13 Nov 2009 17:22:40 -0500

When people hear about an impending meteor shower, their first impression may be of a sky filled with shooting stars pouring down like rain.

Such meteor storms have actually occurred with the annual Leonid meteor shower of November, such as in 1833 and 1966, when meteor rates of literally tens of thousands per hour were observed.

In more recent years, most notably 1999, 2001 and 2002, lesser Leonid displays of up to a few thousand meteors per hour thrilled skywatchers. This year will be not set any records, but the Leonids — set to peak early Tuesday morning, Nov. 17 — should offer a better-than-average display.

Tricky forecasting

The Leonid meteors are debris shed into space by Comet Tempel-Tuttle, which swings through the inner solar system at intervals of 33.25 years, looping around the sun then heading back into the outskirts of the solar system. With each visit the comet leaves behind a trail of dust in its wake.

Plenty of the comet's old dusty trails litter the mid-November part of Earth's orbit and the Earth glides through this debris zone every year. But predicting exactly what's out there is tricky.

On special occasions we'll pass directly through an unusually concentrated dust trail, or filament, which can spark a meteor storm resulting in thousands of meteors per hour. That indeed is what transpired in 1999, 2001 and 2002. Since Comet Tempel-Tuttle comet passed near the sun (and in doing so crossed Earth's orbit) in 1998, it was in those years immediately following its passage that the Leonids put on their best show.

But the comet has since receded out to some 1.8 billion miles from the sun, having taken most of those dense filaments of dust with it. That's why this year, during the predawn hours of Nov. 17, when the Leonids traditionally should be at their most numerous, we now expect to see no more than 10 meteors per hour, even with the promise of this year's excellent viewing conditions thanks to a New moon.

Still – for some parts of the world, a far more prolific Leonid show could be in the offing this year. For although Comet Tempel-Tuttle is now far removed from the inner solar system, independent studies by several noted meteor scientists suggest that the Earth will pass through several notable trails of meteor activity in 2009. We'll list these encounters below in chronological order, including the prime regions of visibility.

Nov. 17, early a.m., Europe, western Africa/North America

The first cloud of comet dust was released from the nucleus of Tempel-Tuttle back in the year 1567. North America will be turned toward the constellation Leo when these particles begin pelting the upper layers of our atmosphere, some 80 to 100 miles above us. Earth's encounter with the comet dust is going to be brief – possibly no more than several hours long.

Unfortunately, we won't be going directly through the center of cloud, but rather skim through its outer edge on Nov. 17, chiefly between about 4:30 and 10:30 GMT. As a consequence, the meteor rate is not expected to get much higher than 20 or 30 per hour (on average about one meteor sighting every two or three minutes). Still, this is about two to three times the normal Leonid rate.

At the beginning of this window, it will still be dark across Europe and western Africa with Leo high up in the southeast sky, but within an hour the sky will be brightening as sunrise approaches, soon putting an end to meteor watching.

North Americans – especially those living near and along the Atlantic Seaboard – will be able to watch for Leonids from after 1 a.m. local time right on until the first light of dawn, which comes soon after 5 a.m. local time.

Those in the eastern U.S. and Canada are especially favored because Leo will be high in the southeast sky between 3:30 and 5:30 a.m. EST, just before Earth is expected to exit the meteor cloud. For the West Coast, this translates to 12:30 to 2:30 a.m. PST, when Leo is much lower down in the eastern sky.

From Hawaii, Leo will be coming up above the east-northeast horizon right around the time that Earth is exiting the meteor cloud (12:30 a.m. Hawaii Time). However ... this circumstance could lead to the appearance of a few long-trailed Earth-grazing meteors, due to meteoroids that skim along a path nearly parallel to Earth's surface.

Although the overall meteor numbers are expected to be modest at best, the particles that produce them might be larger than the usual flecks of dust that comprise the Leonid swarm. Recall that this cloud of comet particles was released into space in 1567. When such "comet bits" circle the sun for many hundreds of years, the tinier (dust grain) material tends to be pushed away from the sun and dispersed by the pressure of solar radiation. Conversely, because they are relatively unaffected by radiation pressure and leave the comet nucleus with less velocity than their smaller brethren do, the larger pebble-to-marble sized particles tend to linger for a much longer time.

The result could be meteors that are predominantly bright. Watch for the possibility of catching sight of a fireball or bolide (a meteor that silently explodes like a strobe along its path). About half might leave luminous trains lasting anywhere from a few seconds to a few minutes. Indeed, catching sight of even one such meteor will make the vigil of a cold November night worthwhile!

Nov. 18 early a.m., Asia/India/Indonesia

The "Main Event" in 2009 is expected to take place when the Earth has rotated about 12 to 14 hours after passing through the first round of comet dust from 1567. Astronomers Jeremie Vaubaillon (France), Mikhail Maslov (Russia), David Asher (Ireland), and Bill Cooke and Danielle Moser (NASA's Meteoroid Environment Office/MEO) are all in agreement that material that was ejected from the nucleus of Tempel-Tuttle during the years 1466 and 1533 will likely produce a very strong meteor display over much of Asia, India and Indonesia.

There is a high level of confidence that an outburst of bright meteors will occur. This is based mainly on the fact that last year, Earth encountered material that was shed by the comet in 1466 produced about 100 Leonids per hour. This year, Earth will cross through that same 1466 stream again, but much closer to the center of that particular comet cloud. In addition, at about the same time, the Earth will also be passing through dust ejected by the comet in 1533. The consensus forecast among the astronomers for this year suggests rates of anywhere from 130 to perhaps 300 Leonids per hour, but trying to hash out a specific number when two different streams literally coalesce with each other makes a forecast much more difficult to make; it could even be less or it could be much more.

The Earth is expected to pass through the densest parts of the two dust clouds at around 21:40 GMT on Nov. 17, though heavy meteor activity is possible for about an hour or two on either side of this time.

From much of Asia, India and Indonesia, the corresponding calendar date will be Nov. 18. It will be 12:40 a.m. in Moscow; 3:10 a.m. in Mumbai; 4:40 a.m. in Jakarta and 5:40 a.m. in Beijing, Unfortunately from Tokyo and across Australia, the sun will have already risen, effectively hiding the meteor outburst. Conversely, from Europe it will be after sunset on Tuesday evening, but although it will be nighttime, Leo will have not yet risen above the horizon, so the outburst will not visible.

Nov. 18 predawn hours, Europe/western and central Africa

As a late addition, Jeremie Vaubaillon also suggests that some Leonid activity "might" be generated by a very old trail of comet debris dating back to the year 1102. This material, however, is more than 900 years old and has made no less than 27 revolutions around the sun.

As a result, it could very well be almost completely dispersed and not provide any activity at all.

But at 3:29 GMT on Nov. 18, Earth will pass within 30,000 mi. (48,000 km) of the center of this trail. "The position of this very old trail is highly uncertain," notes Vaubaillon, "but if confirmed it may produce a noticeable activity. As a consequence, any event related to this one is highly valuable." Europeans, as well as western and central Africa are in the best viewing position should there be anything to see.

Preparing for your meteor watch

No two observers prepare for a meteor vigil the same way. It helps to have had a late afternoon nap, a shower, and to wear all fresh clothing.

Be sure to keep this in mind: at this time of year, meteor watching can be a long, cold business. Expect the ambient air temperature to be far below what your local radio or TV weathercaster predicts.

Watching a meteor shower consists of lying back, looking up at the sky ... and waiting.

When you sit quite still, close to the rapidly cooling ground, you can become very chilled. You wait and you wait for meteors to appear. When they don't appear right away, and if you're cold and uncomfortable, you're not going to be looking for meteors for very long! Therefore, make sure you're warm and comfortable. Heavy blankets, sleeping bags, groundcloths, auto cushions, and pillows are essential equipment.

Warm cocoa or coffee can take the edge off the chill, as well as provide a slight stimulus. It's even better if you can observe with friends. That way, you can keep each other awake, as well as cover more sky.

Keep in mind that any local light pollution or obstructions like tall trees or buildings will reduce your making a meteor sighting. Give your eyes time to dark-adapt before starting. Probably the best bet is to rest on a lawn lounge, all the way back, so you can look up and see the whole sky. When you see a streak, mentally run it backwards across the sky. Do the same with the second and third and note where their paths cross. Right there will be the Sickle of Leo, and that's where the Leonid radiant will be. The constellation of Leo does not come fully into view above the east-northeast horizon until after 1 a.m. local time, so that would be the best time to concentrate on looking for Leonids.

Lastly, because the Leonids are moving along in their orbit around the sun in a direction opposite to that of Earth, they slam into our atmosphere nearly head-on, resulting in the fastest meteor velocities possible: 45 miles per second. Such speeds tend to produce meteors with hues of white, blue, aquamarine and even green.

Blazing Rocket Launch Could Surprise East Coast

Tue, 05 May 2009 07:35:16 -0400

Should a rocket blast off on schedule early Tuesday evening from NASA's Wallops Island Flight Facility in Virginia, a potentially spectacular sight might be visible across a wide swath of the U.S. Eastern Seaboard, weather permitting.

It would be only the third attempt at launching an orbital rocket from this coastal Virginia range — located just south of Assateague Island — in the last 13 and a half years.

The first time NASA attempted an orbital launch from Wallops, in October 1995, the liftoff of a 50-foot-tall Conestoga rocket ignited normally, but the vehicle exploded over the Atlantic just 46 seconds later. A problem with the rocket's guidance system was blamed.

Then in December 2006, a 69-foot-long, 5-foot wide, 35-ton, four-stage Minotaur I rocket successfully launched the TacSat-2 satellite, carrying a semisecret payload from the Pentagon's Missile Defense Agency.

Now another Minotaur I rocket awaits liftoff from the Wallops Flight Facility Tuesday, May 5, no earlier than 8 p.m. EDT. A home video of a Minotaur launch out West in 2005, shot by Doc Searls with his son, shows they can be spectacular crowd-pleasers.

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While many Westerners are fairly familiar with such sightings, they are all but unknown in the East and so may end up surprising millions of people should the Minotaur I lift off on schedule.

The chief goal of this flight is to place the 880-pound TacSat-3 satellite with its trio of payloads that will offer real-time imagery (within 10-minutes of collection), sea-based information transmitted from ocean buoys and plug-and-play avionics to assist warfighters in keeping one step ahead of their adversaries.

In addition, three "cubesats" will be launched as secondary payloads on the TacSat-3 mission.

A launch window from May 5 to 9, from 8:00 p.m. to 11:00 p.m. EDT each day, has been established to take into account bad weather or equipment glitches (see "Final Points" below). A launch after 8:00 p.m. EDT would occur just after sunset along the entire Atlantic coastline.

What to expect

Over the years, similar rocket firings have routinely taken place from California's Vandenberg Air Force Base.

Rocket launches that have occurred around the time of sunrise or sunset have left long, glowing contrails in their wake that have been seen for a few hundred miles across the desert Southwest, often becoming contorted by high level winds into strange and exotic patterns and sometimes, prismatic colors.

Based on a very similar launch from Wallops Island in December 2006 and similar dusk and dawn launches from Vandenberg as a guide, I've determined that it should be possible that Tuesday's post-sunset launch may be visible as far north as southern Maine, as far south as northeastern Florida and as far west as eastern Kentucky.

The rocket will be launched on a southeast trajectory. Approximately six minutes after launch it will be passing north of Bermuda. Three minutes later it will reach orbital altitude over the middle of the North Atlantic.

Observers who are situated within about 800 statute miles of the Wallops Island Flight Facility appear to have a reasonable chance of catching a view of the Minotaur I contrail within the first few minutes after launch.

The key to making a sighting is to have a clear, unobstructed view of the horizon in the direction of Wallops Island.

For example, a viewer in Raleigh, North Carolina should look toward the northeast; in Boston, Massachusetts look southwest; in Wheeling, West Virginia it will be due east.

Areas farther to the northeast (toward southern New England) have an advantage since skies will be darker — sunset will come somewhat earlier than it will along the Mid-Atlantic Coast. At Wallops, it's at 7:57 p.m., but from Boston it's at 7:49 p.m.

Farther to the west across the Ohio Valley, the sun will still be above the horizon, so the launch may only be barely visible, if at all, against the blue daytime sky. But should the launch be delayed by just 30 minutes, sunset will arrive, sufficiently darkening local skies.

Final points

The Minotaur I is a launch vehicle sometimes called "half man and half beast" because it combines features of the Minuteman missiles and Pegasus rockets. It also merges space technologies designed for both military and commercial ventures.

Another factor in this launch is the upcoming May 11 launch of the Space Shuttle Atlantis at Cape Canaveral, Florida.

According to Wallops Public Affairs officer Keith Koehler, the Wallops tracking systems are needed to support a shuttle Launch. "We have to stand down because of the Space Shuttle launch. We have assets that support the launch. Then I believe there is another launch at the Cape that will be using assets that we use."

Wallops is NASA's cynosure for tracking orbital payloads and receiving meteorological information relating to North America.

And although it has never been used for this purpose, Wallops can also boast that its 8,750-foot runway, usually reserved for winged-aircraft safety tests, is an approved shuttle emergency-landing site.

The latest launch updates are available from NASA here.

Night Shuttle Launch to Be Visible From Most of East Coast

Wed, 11 Mar 2009 08:36:07 -0400

People in the eastern United States will get a great opportunity, weather permitting, to see the Space Shuttle Discovery launched into orbit Wednesday evening.

The shuttle flight (STS-119) will be the 28th to rendezvous and dock with the International Space Station (ISS), and the glow of its engines will be visible along much of the Eastern Seaboard of the United States. A SPACE.com map shows the area of visibility.

To reach the ISS, Discovery must be launched when Earth's rotation carries the launch pad into the plane of the station's orbit. For mission STS-119, that will happen at 9:20:10 p.m. ET on Wednesday, resulting in NASA's second consecutive nighttime launch (the most recent coming on Nov. 14).

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As has been the case with other launches to the ISS, this upcoming launch will bring the shuttle's path nearly parallel to the U.S. East Coast.

What to expect

In the Southeast United States, depending on a viewer's distance from Cape Canaveral, the "stack" (shuttle orbiter, external tank and solid rocket boosters) can be easily followed thanks to the fiery output of the solid rocket boosters.

The brilliant light emitted by the two solid rocket boosters will be visible for the first 2 minutes and 4 seconds of the launch out to a radius of some 520 statute miles from the Kennedy Space Center.

Depending on where you are located relative to Cape Canaveral, Discovery will become visible anywhere from a few seconds to just over 2 minutes after it leaves Pad 39-A.

For an example of what all this looks like from Florida, see video of a night launch made by Rob Haas from Titusville, FL, on Dec. 9, 2006 (the STS-116 mission).

After the solid rocket boosters are jettisoned, Discovery will be visible for most locations by virtue of the light emanating from its three main engines.

It should appear as a very bright, pulsating, fast-moving star, shining with a yellowish-orange glow.

Based on previous night missions, the brightness should be at least equal to magnitude -2; rivaling Sirius, the brightest star in brilliance.

Observers who train binoculars on the shuttle should be able to see its tiny V-shaped contrail.

James E. Byrd shot video of the shuttle from Virginia after a November 2000 night launch. The bright star Sirius briefly streaks through the scene giving a sense of scale and brightness to the shuttle's glow.

By location

Southeast U.S. coastline: Anywhere north of Cape Canaveral, I suggest viewers initially concentrate on the south-southwest horizon. If you are south of the Cape, look low toward the north-northeast. If you're west of the Cape, look low toward the east-northeast.

Mid-Atlantic region: Look toward the south about 3 to 6 minutes after launch.

Northeast: Concentrate your gaze low toward the south-southeast about 6 to 8 minutes after launch.

For most viewers, the shuttle will appear to literally skim the horizon, so be sure there are no buildings or trees to obstruct your view.

Depending upon your distance from the coastline, the shuttle will be relatively low on the horizon (5 to 15 degrees; your fist on an outstretched arm covers about 10 degrees of sky). If you're positioned near the edge of a viewing circle, the shuttle will barely come above the horizon and could be obscured by low clouds or haze.

If the weather is clear the shuttle should be easy to see. It will appear to move very fast; much faster than an orbiting satellite due to its near orbital velocity at low altitudes (30-60 mi). It basically travels across 90 degrees of azimuth in less than a minute.

Discovery will seem to "flicker," then abruptly wink-out 8 minutes and 23 seconds after launch as the main engines shut-down and the huge, orange, external tank (ET) is jettisoned over the Atlantic at a point about 870 statute miles uprange (to the northeast) of Cape Canaveral and some 430 statute miles southeast of New York City.

At that moment, Discovery will have risen to an altitude of 341,600 feet (64.7 statute miles), while moving at 17,579 mph and should be visible for a radius of about 770 statute miles from the point of Main Engine Cut Off (MECO).

Following MECO and ET separation, faint bursts of light caused by reaction control system (RCS) burns might be glimpsed along the now-invisible shuttle trajectory; they are fired to build up the separation distance of the orbiter from the ET and to correct Discovery's flight attitude and direction.

Lastly: before hoping to see the shuttle streak across your local sky, make sure it has left the launch pad!

What happens in case of a scrub?

Because Russia plans to launch a Soyuz spacecraft carrying the next space station commander and flight engineer on Mar. 26, the docked phase of the shuttle mission must be done by then to avoid a conflict.

To get in a full-duration four-spacewalk mission, Discovery must take off by Mar. 13. Should the launch be postponed to Mar. 12, liftoff would come at 8:54 p.m. EDT; on Mar. 13, it would come at 8:32 p.m.

By giving up one or two of the mission's planned spacewalks, along with off-duty time, Discovery could launch as late as Mar 16 or 17 in a worst-case scenario. But that would coincide with bright twilight or sunset for parts of the Eastern Seaboard.

After that, the flight would slip to April 7, which would make it a daytime launch.