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Jan 9, 2006

Hubble Telescope Captures Polaris' Companion Star For The First Time

Long before the invention of the telescope revolutionized navigation, mankind was guided by the ever-present North Star, or Polaris. Now, astronomers working with NASA's Hubble Space Telescope have photographed the close companion of Polaris for the first time. Their findings were presented today at the meeting of the American Astronomical Society in Washington, D.C.

Instead of being a single, stationary point of light as it appears to the naked eye, Polaris is actually a triple star system. One of it's companion stars can be seen easily through small telescopes. But until now, the other star had never been seen.

Two factors made the close companion to Polaris, called, "Polaris Ab"so difficult to see:

  • Proximity -The companion is less than two-tenths of an arcsecond from Polaris. While that translates to 2 billion miles out in space, it is the equivalent to the apparent diameter of a quarter located 19 miles away here on Earth.
  • Brightness - "The brightness difference between the two stars made it even more difficult to resolve them," Howard Bond of the Space Telescope Science Institute said. Polaris is a supergiant, more than two thousand times brighter than our Sun. The companion is a main-sequence star.

Astronomers plan to study the Polaris system's orbits as a way of measuring their masses, one of the toughest tasks for astronomers. Such measurements may someday help measure the distances of galaxies and the expansion rate of the universe.