Hubble captures cosmic fireworks in ultraviolet

Hubble offers a special view of the double star system Eta Carinae's expanding gases glowing in red, white, and blue. This is the highest resolution image of Eta Carinae taken by the NASA/ESA Hubble Space Telescope.

Arp 299: Galactic Goulash

What would happen if you took two galaxies and mixed them together over millions of years? A new image including data from NASA's Chandra X-ray Observatory reveals the cosmic culinary outcome.

Astronomers find a star with a record variation period

Three years ago, Lomonosov Moscow State University astronomers detected a bright star TYC 2505-672-1 that has now faded significantly. The scientists assume that TYC 2505-672-1 is actually a double star system, though the ...

Final kiss of two stars heading for catastrophe

Using ESO's Very Large Telescope, an international team of astronomers have found the hottest and most massive double star with components so close that they touch each other. The two stars in the extreme system VFTS 352 ...

Largest yellow hypergiant star spotted

ESO's Very Large Telescope has revealed the largest yellow star—and one of the 10 largest stars found so far. This hypergiant has been found to measure more than 1,300 times the diameter of the Sun, and to be part of a ...

Bright star reveals new exoplanet

An international team of astronomers at Stellar Astrophysics Centre in Aarhus, Denmark, have discovered a new exoplanet, christened "Kepler-410A b." The planet is about the size of Neptune and orbits the brightest star in ...

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Double star

In observational astronomy, a double star is a pair of stars that appear close to each other in the sky as seen from Earth when viewed through an optical telescope. This can happen either because the pair forms a binary system of stars in mutual orbit, gravitationally bound to each other, or because it is an optical double, a chance alignment of two stars in the sky that lie at different distances. Binary stars are important to stellar astronomers as knowledge of their motions allows direct calculation of stellar mass and other stellar parameters.

Since the beginning of the 1780s, both professional and amateur double star observers have telescopically measured the distances and angles between double stars to determine the relative motions of the pairs. If the relative motion of a pair determines a curved arc of an orbit, or if the relative motion is small compared to the common proper motion of both stars, it may be concluded that the pair is in mutual orbit as a binary star. Otherwise, the pair is optical. Multiple stars are also studied in this way, although the dynamics of multiple stellar systems are more complex than those of binary stars.

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