Scientists can finally figure out the mass of the North Star, or Polaris, after the Hubble Telescope has captured the first image of a hidden second companion of the North Star, U.S. astronomers said on Monday.

With the image of Polaris Ab, astronomers estimated the mass of the North Star at about four times that of our sun. The North Star, more than 2,000 times brighter than the sun, has been used by men as a navigation aid.

The image released Monday displayed a little, faint dwarf star, which is just 3.2 billion km from the North Star. Scientists have detected its presence from its gravity effect upon the North Star, but never seen it.

North Star's first companion, Polaris B, has been known since 1780 and can easily be seen with a smaller telescope.

Astronomers presented the results at the 207th meeting of the American Astronomical Society on Monday.

Source: Xinhua