Outbreak of spousal violence: a white dwarf caught eating his partner

Unlike the lonely sun, about half stars From the Milky Way galaxy is in an exclusive relationship with another star, as the two orbit each other in a cosmic marriage called the “binary system.”

This week astronomers presented the case of one such marriage failure — a couple living on the edge as stars orbit each other every 51 minutes, the shortest orbital period ever recorded in this unusual class of binary system. The drama now unfolding is another star-devouring one.

The binary system ZTF J1813 + 4251, located in the direction of the constellation Hercules 3,000 light-years from Earth, belongs to a class called “cataclysmic variable stars”, in which a Sun-like star orbits around a white dwarf, dense as the remains of a dead star.

The term “variable” means that the brightness of the system is constantly fluctuating to observers on the ground. And the term “catastrophic” simply refers to the fact that brightness changes dramatically, up to 10,000 times in some cases.

bad relationship

Over the course of millions of years, the distance between the two stars has decreased, to the point that they are now less distant from Earth than the Moon.

“Imagine the moon crossing the sky 10 times every night. We’re talking about such speeds,” Kevin Berg, an MIT astrophysicist and lead author of the study published in temper nature.

But the symbiosis of the spouses in such a close relationship does not mean that the two stars treat each other well – the white dwarf mercilessly sucks material from its partner.

The unlucky bigger star orbits the temperature of the Sun but has lost so much material that it is now only 10% the diameter of the Sun and is comparable in size to Jupiter. The mass of the white dwarf is equal to 55% of the mass of the Sun, but it is concentrated in a sphere whose diameter is only 1.5 times the diameter of the Earth.

The big star was nearing the end of its life and was about to transform into a red giant and then a white dwarf. But the process was halted due to cannibalism.

“The white dwarf interrupted the end of his partner’s life cycle and started eating him,” Borg said.

In fact, the attraction of the white dwarf is so strong that the victim lost its spherical shape and was flattened (photo above).

Astronomers have detected more than 1,000 cataclysmic variable binaries so far, but few of them move with orbital periods of less than 75 minutes.

The pair examined in the study is very fast at 51 minutes, but doesn’t hold the record when compared to other classes of duos.

The shortest orbital period measured is 5 minutes 21 seconds for two white dwarfs orbiting each other.

“There are a lot of strange things going on in space,” Berg commented.