Astronomers using the Hubble Space Telescope have revealed something just as constant as the North Star: a hidden companion.

Astronomers now have photographic proof that Polaris, as the bright star and navigational aid is formally called, has two stellar companions.

The first, Polaris B, has been known since 1780 and can easily be seen with even a smaller telescope; the presence of the second, Polaris Ab, has been inferred but eluded direct detection because it was close to Polaris and relatively faint.

The North Star is a super-giant more than 2,000 times brighter than the sun, while its newly photographed second companion is a dwarf star just 2 billion miles from it, astronomers said. They presented the results Monday at the 207th meeting of the American Astronomical Society.

"With Hubble, we've pulled the North Star's companion out of the shadows and into the spotlight," said Howard Bond, of the Space Telescope Science Institute. The Baltimore institute conducts science operations for the orbiting Hubble.