Astronomers Spot Massive Blue Stars Beginning To Merge
by Janet Fang
Photo credit: Artistic rendering of MY Cam system. The proportions between the components reflect the analysis results. The stars are deformed by its very fast rotation and the gravitational pull of the companion / Javier Lorenzo, Universidad de Alicante
In the Giraffe constellation 13,000 light-years away, MY Camelopardalis is a massive binary system made up of two blue (that is, very hot and very bright) stars. They’re so close, they’re about to merge into a supermassive star—a process no one has ever seen before. Even though MY Cam is the first known example of a supermassive merger progenitor, astronomers studying the system say that most massive stars are created through mergers with smaller ones. The findings were published in Astronomy & Astrophysics last week.
Stars that move alone like our sun are the minority. Most stars in our galaxy were formed in binary or multiple systems, where they’re tied by gravity to a companion star. In some of these systems, the stars might appear to eclipse one another if their orbital planes face Earth. For that reason, MY Cam was thought to be a single star up until a decade ago.
Using observations from the Calar Alto Observatory in Spain, a team led by Javier Lorenzo from the University of Alicante found that the eclipsing binary MY Cam is made up of one star that’s 38 times the mass of our sun, and another that’s 32 solar masses. The two jumbo stars are very close together: Their orbital period is just under 1.2 days, making it the shortest orbital period known for these types of stars. In order to complete a full turn so quickly, the stars must be in extremely close contact (pictured above)—so close that they’re actually touching and their outer layer material are mixing together in what’s known as a common envelope.
The members of this contact binary are moving around each other at a speed of over one million kilometers an hour. Additionally, the tidal forces in between make them rotate about themselves in just over a day—almost like Earth, except they each have a radius that’s 700 times bigger. The sun, by comparison, makes a full turn once every 26 days.
Not only is MY Cam the most massive eclipsing binary, it’s also the most massive binary with components so young they haven’t even begun to evolve, according to a news release. The stars are less than two million years old, National Geographic explains, and they were probably formed as we see them today. The researchers expect the two will merge into a single object that’s over 60 solar masses before either of them have had the time to evolve significantly.
MY Cam sits at the end of the hindlegs of the Giraffe, and if you’re in the northern hemisphere, you could probably see it using just binoculars pointed between Ursa Major and Cassiopeia.