Black holes increase their own mass by devouring nearby objects. The swallowed stars meet an unfortunate end, but they are a lucky glimpse for scientists who have the opportunity to explore the centers of dormant galaxies. Recently, an MIT team discovered 18 new tidal disruption events and reached a conclusion consistent with model predictions: supermassive black holes swallow up the mass of a star every 50,000 years on average.
Tidal disruption event (TDE) refers to the violent process of “spaghettification” when a star approaches a supermassive black hole (SMBH) and is pulled by the black hole’s tidal force. At this time, part of the star’s mass enters the accretion disk around the black hole, and The black hole swallowing matter will temporarily produce extremely bright electromagnetic radiation, causing the originally invisible black hole to appear.
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There is a supermassive black hole in the center of most large galaxies. For example, our Milky Way has a mainly dormant supermassive black hole, Sagittarius A*, with a mass of about 4.3 million times the sun. But if you look deeper into the universe, you will find more supermassive black holes with masses tens of billions of times that of the sun.
Explosions and radiation caused by the accumulation of stellar debris may be unique signs of the existence of dormant black holes in the centers of galaxies. Therefore, astrophysicists can estimate the characteristics of supermassive black holes and their destruction of stars by studying tidal disruption events, such as the exact mass. In recent years, Over the past decade, physicists have developed many models to calculate the accretion rate (the rate at which stellar material falls back into a supermassive black hole during a TDE), but there is still uncertainty about the accuracy of the resulting approximations.
In 2022, astronomers proposed a new model referred to as CN22. Its TDE peak time span and accretion rate are very consistent with hydrodynamic simulations, and can unlock key information about supermassive black holes and swallowed stars.
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▲ The MIT team discovered 18 new tidal disruption events. (Source:MIT）
Recently, a group of MIT teams analyzed the infrared light data of the NEOWISE satellite and discovered 18 new tidal disruption events in which black holes swallowed stars. Their conclusions enhanced the accuracy of the CN22 model. Among them, the properties of the destroyed stars were related to the peak time of the TDE accretion rate. The span doesn’t matter much.
In other words, the peak fallback rate actually has nothing to do with the mass and age of the destroyed star, but is almost entirely determined by the mass of the supermassive black hole. This is a key indicator that the CN22 model can help researchers limit the mass of the black hole.
The team’s analysis also confirmed the frequency of tidal disruption events, in which the supermassive black hole at the center of any galaxy chaotically engulfs a star every 50,000 years, closer to theoretical predictions by physicists.
The findings may also explain why tidal disruption events do not radiate too much energy, which the team believes is due to dust absorbing visible light, X-rays, and extreme ultraviolet radiation from TDEs.
The research conclusion allows us to temporarily stop thinking about strange physics to explain the extreme phenomena we see, and also allows scientists to better understand the mechanism behind how stars are torn apart and swallowed by black holes.
new paperPublished in the Astrophysical Journal.
(Source of first picture:pixabay）
