The pulsar and white dwarf pair emit gravitational waves and the binary star system gradually loses energy.
Thus it is that a neutron star in a binary star system gets to spend its retirement years as a millisecond radio pulsar.
Secondly, the detection of multiple planets demolishes once and for all the lingering doubts of some astronomers that the single planets found around other stars are not planets at all, but small, faint components in otherwise conventional binary star systems.
This follows the discovery last year by Maciej Konacki, of the California Institute of Technology, of a gaseous giant orbiting a star that is itself orbited by a binary-star system.
Even stars that are born far away from a giant are still likely to be part of a binary or triple star system.
The discovery of exoplanets in binary and triple-star systems raises the prospect that the galaxy houses many more such objects than was previously thought.
These might include, for example, binary stars, where one star orbits another, blocking some of the light as the stars transit each other.
Now, an international team of astronomers has trained the Fermi space-based gamma ray telescope on V407 Cygni, a "binary" system comprising a white dwarf star and a red giant companion, 9, 000 light-years away.
Standard Type Ia supernovae are binary systems in which a white dwarf star draws so much matter from its companion (often a red giant) that it undergoes a kind of energy overload and detonates.
Astronomers using the United Kingdom Infrared Telescope (UKIRT) in Hawaii discovered the four star pairs, each of which is a binary system in which two stars circle each other in less than four hours.
MSN: 'Impossible' stars found in our galaxy - Technology & science - Space - Space.com | NBC News
KELT-2Ab orbits a star that is slightly bigger than the sun, within a binary system called HD 42176.
MSN: Newly discovered alien planet 'resets the bar for weird'
It may be that the binary pair stops the oscillations on the red giant by tugging on the star's surface at just the right times.
Most stars in the galaxy are, in fact, in binary systems, and astronomers have been wondering whether the gravity of a second star nearby might disrupt a dust disc too much for planets to coalesce.
Our sun does not orbit another star, but roughly half of the stars in our Milky Way galaxy do, as part of a binary system.
MSN: 'Impossible' stars found in our galaxy - Technology & science - Space - Space.com | NBC News
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