Astronomers have observed a pair of stars locked in a death spiral, and their dance of doom is shedding more light on how gravity works.
The system, called ZTF J2130, is located about 4,000 light years away. Although astronomers have known about this system for a long time, this is the first time they have observed it with such high clarity.
This is a very old system. One of the stars is a white dwarf, the white-hot remnant of the core of a star similar to the Sun. The other is a so-called subdwarf star, which is a small star nearing the end of its life cycle. The two stars are so close to each other that they orbit in less than 40 minutes. In fact, they had already started kissing. Their mutual gravity is so strong that they are stretched and distorted, with material from the subdwarf flowing onto the white dwarf's companion.
Because stars are quite massive and move very quickly, they emit gravitational wavesThis emission of gravitational waves drains the system's energy, bringing the two stars closer each year.
Using a combination of data from the Oskar Lüning Telescope at the Hamburg Observatory in Germany and the CAHA Observatory in Spain in Germany and Spain, astronomers undertook a painstaking campaign to measure the orbital period as accurately as possible. They found that the orbit was slowly decaying; With every second, the orbital period decreases by about two trillionths of a second.
This is consistent with calculations based on our current theoretical understanding of gravity. But scientists sought to go beyond Einstein's theory. general theory of relativity for more than a century, so any opportunity to test it immediately sparks interest.
Astronomers have discovered that a future gravitational-wave observatory known as the Space Laser Interferometer The antenna (LISA) must be able to directly measure gravitational waves emanating from this system. European Space Agency plans to launch LISA in the 2030s, and this star couple will still be around in the next decade.
When the stars finally merge, they will produce a supernova-level explosion that may be bright enough to be seen with the naked eye. For now, before we can enjoy these fireworks, we just need to check the gravity.
