![]() ![]() GALEX, which we attribute at least in part to cosmic variance in the small We find that the FUV galaxy number counts are higher than those reported by (spectroscopic or photometric) for the detected sources are in the range 0<1, by H. "Our ultimate goal is the get an accurate mass for Polaris," said Evans. ![]() In that time, the movement of the small companion in its 30-year orbit around the primary should be detectable. The researchers plan to continue observing the Polaris system for several years. "With the best instruments like Hubble, we can push farther into space and study more of them up close." "We only have the binary stars that nature provided us," added Bond. "Studying binary stars is the best available way to measure the masses of stars," said science team member Gail Schaefer of STScI. Knowing their mass is the most important ingredient in this understanding. Cepheids' brightness variations are used to measure the distances of galaxies and the expansion rate of the universe, so it is essential to understand their physics and evolution. Measuring the mass of a star is one of the most difficult tasks facing stellar astronomers.Īstronomers want to determine the mass of Polaris accurately, because it is the nearest Cepheid variable star. "With Hubble, we've pulled the North Star's companion out of the shadows and into the spotlight."īy watching the motion of the companion star, Evans and her colleagues expect to learn not only the stars' orbits but also their masses. Polaris is a supergiant more than two thousand times brighter than the Sun, while its companion is a main-sequence star. "The brightness difference between the two stars made it even more difficult to resolve them," stated Howard Bond of the Space Telescope Science Institute (STScI). At the system's distance of 430 light-years, that translates into a separation of about 2 billion miles. The companion proved to be less than two-tenths of an arcsecond from Polaris - an incredibly tiny angle equivalent to the apparent diameter of a quarter located 19 miles away. "The star we observed is so close to Polaris that we needed every available bit of Hubble's resolution to see it," said Smithsonian astronomer Nancy Evans (Harvard-Smithsonian Center for Astrophysics). They presented their findings today in a press conference at the 207th meeting of the American Astronomical Society in Washington, D.C. And while one companion can be seen easily through small telescopes, the other hugs Polaris so tightly that it has never been seen - until now.īy stretching the capabilities of NASA's Hubble Space Telescope to the limit, astronomers have photographed the close companion of Polaris for the first time. The North Star is actually a triple star system. But there is more to the North Star than meets the eye. We tend to think of the North Star, Polaris, as a steady, solitary point of light that guided sailors in ages past. Four Successful Women Behind the Hubble Space Telescope's Achievements.Characterizing Planets Around Other Stars.Measuring the Universe's Expansion Rate. ![]()
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