Two dying stars, spinning around each other every 39 minutes, have just been discovered by astronomers. In a few million years, they will collide and merge, to be born again as a new single star.
The two stars, located 7,800 light-years away in the constellation Cetus, are white dwarfs: they are dying stars, in their final evolutionary state.
“These stars have already lived a full life. When they merge, they’ll essentially be ‘reborn’ and enjoy a second life,” said Smithsonian astronomer Mukremin Kilic (Harvard-Smithsonian Center for Astrophysics), lead author on the paper announcing the discovery. This paper will be published in the Monthly Notices of the Royal Astronomical Society.
Only a few similar systems are known in our Milky Way Galaxy, home to 100 billion stars. Most of them were found by Kilic and his colleagues. The latest system, with the catchy name of SDSS J010657.39 – 100003.3, will be the first one to merge and be reborn.
It consists of a visible star and an unseen companion, both believed to be made of helium. The presence of the latter is betrayed by the visible star’s motion around it. The visible one weighs approximately 17% as much as the Sun, while the other weighs about 43% as much. The two white dwarfs orbit each other at a distance of about 225,000 kilometers (140,000 miles), at an incredible speed of 1.6 million kilometers per hour (1 million miles per hour). They are closer to each other than the Moon is to the Earth, completing one orbit in only 39 minutes.
Because they whirl around so close to each other, they produce a huge amount of gravitational waves, or “ripples” in the spacetime continuum. As these waves are carrying away orbital energy, the stars are getting closer and closer together in a spiral movement: in about 37 million years, they will collide and merge.
As the pair of white dwarfs is too light, they will not explode as a supernova whan they collide. Instead, they will start a new life as a single star fusing helium, shining like its “parents” once did, a very long time ago.