Remnant of stellar collision revealed as new type of pulsating star

 A team of astronomers from the UK, Germany and Spain have observed the remnant of a stellar collision and discovered that its brightness varies in a way not seen before on this rare type of star.
By analyzing the patterns in these brightness variations, astronomers will learn what really happens when stars collide. Stars like our Sun expand and cool to become red giant stars when the hydrogen that fuels the nuclear fusion in their cores starts to run out.

Many stars are born in binary systems so an expanding red giant star will sometimes collide with an orbiting companion star. As much as 90 percent of the red giant star's mass can be stripped off in a stellar collision, but the details of this process are not well understood. Only a few stars that have recently emerged from a stellar collision are known, so it has been difficult to study the connection between stellar collisions and the various exotic stellar systems they produce.

When an eclipsing binary system containing one such star turned up as a by-product of a search for extrasolar planets, Dr. Pierre Maxted and his colleagues decided to use the high-speed camera ULTRACAM to study the eclipses of the star in detail. These new high-speed brightness measurements show that the remnant of the stripped red giant is a new type of pulsating star.
The discovery is published in the journal Nature.