Illustration of a white dwarf
At 1.2 times the mass of the Sun, white dwarf RX J0648 has the fastest known rotation. It should explode and become a supernova within a maximum of 100,000 years — a mere trifle in astronomical terms.
Has it ever happened that you were enjoying some delicious food that you ended up eating more than you should have? Well, something like this is happening with the star RX J0648, which is about. 1700 light years from Earth. The problem is that this star is a “vampire” white dwarf that is stealing so much matter from its neighbor that it could end up exploding soon — in astronomical terms, of course.
The star in question is the neighbor of HD 49798, a star that has about 1.5 times the mass of the Sun. The system has intrigued astronomers since 1997, when they discovered x-ray emissions coming from there. As early as 2009, the XMM-Newton space telescope showed that there was, in fact, a white dwarf star in the system — which is RX J0648.
With 1.2 times the mass of the Sun, RX J0648.0–4418 is considered the white dwarf with fastest rotation ever seen. It completes a revolution around itself every 13 seconds, and in the meantime, it captures matter from its neighbor. Now, a new analysis by Sandro Mereghetti, a researcher at the National Institute of Astrophysics, confirms that the star’s “agility” may be related to its shrinkage.
In addition to its impressive rotation, RX J0648. 0–4418 is one of the most massive white dwarfs ever found. Normally, these stars are at most 0.6 times the mass of the Sun, but this has double this value. This means the white dwarf is close to the so-called Chandrasekhar Limit, which determines when a star has enough mass to explode in a supernova.
“There is a limit mass that a white dwarf can sustain. It’s about 1.4 times the solar mass. The white dwarf in this system is already very close to that limit and is accumulating mass,” said Mereghetti. “Theoretical calculations give slightly different estimates of when this system will go supernova, but they are all less than 100 thousand years old”, explained the author.
Does the time seem long? Well, know that, in fact, it is quite short in astronomical terms — our Sun, for example, is almost 4.6 billion years old. This star’s supernova explosion will be accelerated by the fact that, as the system ages, the speed at which it steals matter increases. Fortunately, there is still plenty of time until then for scientists to study the system.
