Astronomers have recently been fortunate enough to observe a fantastic collision of two neutron stars. However, what happened after still baffles science.
In August of this year, astronomers watched as two neutron stars merged with each other, producing gravitational waves and an enormous explosion. Then scientists did not fully understand what was formed as a result: one colossal neutron star, a black hole, or something else.
Yun-Wei Yu at Central China Normal University and Zi-Gao Dai at Nanjing University in China simulated this explosion (the so-called kilonowa), which in reality can last from several weeks to several months. According to their calculations, one, but a very large neutron star should remain at the site of the collision.
Collision of neutron stars: how it happens
There are three main theories about what could happen in a collision like this. In the first case, a black hole is formed; in the second, a neutron star is obtained, which lives for only a few milliseconds, after which it turns either into a black hole, or into the third option - a stable neutron star. If in this case everything went according to the third scenario, then astronomers were lucky to observe the largest neutron star ever discovered.
The gravitational waves that scientists have observed with LIGO will not be able to clarify the situation. However, here kilonova comes to the aid of scientists.
Because neutron stars originally rotate in a spiral, they can accelerate to about 1/3 the speed of light, explains Edo Berger of Harvard University. When two such stars collide and become one, the object retains this momentum and, as a result, rotates incredibly fast. In the process, a huge star emits energy, which either further accelerates the process, or, on the contrary, slows it down. If a neutron star slows down to the threshold limit, it will inevitably start a spontaneous process to transform into a black hole. The exact mass at which the collapse of a celestial body occurs is still unknown - it is only clear that the star must be colossal.
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Thus, astronomers can only observe the kilonova. An increase in the level of radiated energy will mean that the two stars have successfully merged into one. “For a neutron star, a kilonova is a radiation of energy in different directions, while for a black hole, it's just a powerful pulse in one direction, a kind of 'jet stream that will cause a noticeable gamma-ray burst,' says Berger.
Now the opinions of scientists differ. Yu and Dai are confident that their mathematical model is correct and that a huge neutron star was formed as a result. Berger, in turn, points to a powerful gamma-ray pulse and is confident that the collision led to the emergence of a new black hole. In addition, he notes that the energy surge in the Chinese scientists' model overshadows the explosion itself, which astronomers observed with telescopes.
The situation should be resolved in the next few weeks. If earlier all theories were based on hypotheses, now researchers only have to decipher the factual data and finally find out what happened as a result of such a phenomenal catastrophe.
Vasily Makarov