Astronomers discover helium-burning white dwarf

A white dwarf star can explode as a supernova when its mass exceeds the limit of about 1.4 solar masses. A team led by the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching and involving the University of ...

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 ...

Scientists discover planetary system orbiting Kepler-47

News flash: The Milky Way galaxy just got a little weirder. Back in 2011 astronomers were amazed when NASA's Kepler spacecraft discovered a planet orbiting a double star system.  Such a world, they realized, would have double ...

Pulsating star mystery solved

(PhysOrg.com) -- By discovering the first double star where a pulsating Cepheid variable and another star pass in front of one another, an international team of astronomers has solved a decades-old mystery. The rare alignment ...

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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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