Pluto Gets 14 New Neighbors

Astronomers have discovered a cache of 14 large space rocks beyond the orbit of Neptune while sifting through archival observations from the Hubble Space Telescope.

Icy rocks like the newfound objects are known as trans-Neptunian objects because they typically reside outside Neptune's orbit. These objects include the former planet Pluto, now classified as a dwarf planet, as well as comets like the famed Halley's comet.

The newfound objects range from 25 to 60 miles across (40 to 100 kilometers), said the researchers.

Most trans-Neptunian objects are faint and hard to spot. To find the new group, researchers searched through Hubble photos for the telltale streaks of light that images of these rocks leave as they move through space during time-lapse exposures. After its initial success, this method could reveal hundreds more trans-Neptunian objects over time, hopeful scientists say.

"Trans-Neptunian objects interest us because they are building blocks left over from the formation of the solar system," said study leader Cesar Fuentes of Northern Arizona University.

These objects are similar to asteroids but lie farther from Earth. Asteroids generally orbit in the inner solar system, out to the orbit of Jupiter.

By measuring the trans-Neptunian objects' motion across the sky, the astronomers were able to calculate each object's orbit and distance from the sun. The researchers were able to estimate the size of each object by combining observations on their distance, brightness and reflectivity,

This initial study examined only one-third of a square degree of the sky, meaning that there is much more area to survey, researchers said. Fuentes, who formerly was with the Harvard-Smithsonian Center for Astrophysics, said he and his colleagues intend to continue their search for trans-Neptunian Objects.

"We have proven our ability to detect and characterize TNOs even with data intended for completely different purposes," Fuentes said.

The findings will be described in an upcoming issue of the Astrophysical Journal.

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