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

Polaris, as the bright star and navigational aid is formally called, now has two known stellar companions. The first, Polaris B, has been known since 1780 and can easily be seen with even a smaller telescope; the second, Polaris Ab, had long 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 3.2 billion kilometres from it, astronomers said. They presented the results Monday at the 207th meeting of the American Astronomical Society.

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Originally posted by Agent 204:
Cool. I presume the line about the second companion star having "long evaded direct detection" means that it was detected spectroscopically a long time ago and that it's only now that we've been able to actually see it.

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Polaris Ab, an otherwise nondescript solar-type star, had only been recorded by spectrometers and managed to avoid being photographed — until now....

Polaris Ab was a tricky star to spot. While spectroscopic studies had told astronomers much about the object, including its orbit, those same observations failed to reveal the separation between the primary and Polaris Ab. The new Hubble images show the companion to be just 3.2 billion kilometers away (2 billion miles), translating to a scant angular separation of 0.2 arcsecond. Further hampering the detection was the brightness difference between the two, as the light from much smaller Polaris Ab is nearly overshadowed by its supergiant big brother.

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