2021-01-16

What happened to the universe? The galaxy flashes every 114 days, and scientists finally find the answer

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What happened to the universe? The galaxy flashes every 114 days, and scientists finally find the answer

This strange galaxy is named ESO 253-G003. In the center of the galaxy, a star is orbiting a supermassive black hole. Every 114 days, the distance between the two is close enough for the black hole to suck away some of the star’s material, resulting in a bright flash that spans multiple bands. Then the star gets farther and farther away from the black hole, until the next time it approaches the black hole again, some of the material is sucked away to light up. Because of the regularity of flashes, astronomers have given this galaxy the nickname “Old Faithful”.

What happened to the universe? The galaxy flashes every 114 days, and scientists finally find the answer(1)

The first author of this study, Hawaii University astronomer Anna Payne said, “These are the most regular and frequent multi-band flashes we have observed from the center of the galaxy. This provides us with a unique opportunity to study the “Old Faithful” galaxy. ”

Penn added, “We believe that the supermassive black hole in the center of the galaxy caused the explosion because it is eating up some of the material of the giant star orbiting it.”

In November 2014, the All Weather Automatic Supernova Search System (ASAS-SN) detected these flashes for the first time. At the time, astronomers believed that this phenomenon originated from supernovae in the galaxy ESO 253-G003.

But in 2020, when Payne was looking at the data on ESO 253-G003 on ASAS-SN, she found multiple flashes from the same place.

Payne sorted out a total of 17 flash occurrences, each with an interval of about 114 days. She and her team then predicted that the galaxy will flash again on May 17, September 7, and December 26, 2020, with the results as expected.

Researchers named the repeated burst of flashes ASASSN-14Ko. This regular phenomenon means that they can use the powerful Transiting Exoplanet Survey Satellite (TESS) of the National Aeronautics and Space Administration (NASA) A more detailed observation of the flash that occurred in May last year. Prior to this, the observation results of other instruments have provided researchers with data in different wavelength ranges.

The Ohio State University astronomer Patrick Vallely (Patrick Vallely) said, “TESS provided a detailed picture of the special flashes of galaxies, but due to the special way the satellite explores space, it cannot observe To all the flashes of eruption.” Valerie said that TESS can only observe an area for 27 days. “Although ASAS-SN collects fewer flash burst details, it covers a wider range, which is very important in the observation of special flashes. These two research methods can complement each other.”

Researchers initially speculated that because supernova explosions would destroy the original stars, they would only flash once in the night sky, and then disappear, because such an event would destroy the original stars; so bright light was repeatedly produced in the visible, ultraviolet, and X-ray bands It must be something else.

Actually, this is not the first time that a supermassive black hole swallows a star and produces regular flashes. A similar flash with a period of 9 hours was discovered last year. But the situation of ESO 253-G003 is more special.

This is because the researchers found that ESO 253-G003 are actually two galaxies in the final stage of merger, which means that there should be two supermassive black holes in the center of the galaxy.

Some studies have shown that two interacting supermassive black holes can cause flashes to occur repeatedly. However, through observations, researchers believe that the two supermassive black holes at the center of ESO 253-G003 are too far apart to produce flashes repeatedly.

Another possibility is that when a black hole swallows matter, an accretion disk will be formed, and a star will repeatedly traverse the accretion disk as it orbits the black hole, producing dazzling light. But the researchers also ruled out this. Because if this star traverses the accretion disk at different positions and angles, the flashes it produces should be different each time; but the observation results show that the flashes from the center of the galaxy ESO 253-G003 are almost identical.

The third possibility is repeated tidal destruction events. Specifically, a larger-mass celestial body continuously strips matter from a smaller celestial body orbiting it.

Researchers speculate that if a star orbits the black hole along an eccentric orbit, and the revolution period is exactly 114 days, then when it approaches the black hole, a tidal destruction event will occur, and part of the star’s material will be lost to the black hole. Stripping off, the star continues to orbit the black hole.

When these exfoliated substances collide with the substances in the accretion disk, flashes will be produced. This seems to be what is happening in the ESO 253-G003 galaxy.

Considering this situation, the research team deeply analyzed the observation results. They studied the light curve of each flash and compared it with other known black hole tidal destruction events. They determined that the star is likely to orbit a supermassive black hole with a mass equivalent to 78 million suns.

Every time it approaches a black hole, the star loses about 0.003 solar mass (that is, the mass of 3 Jupiters), which is enough to form a flash that can be observed by astronomers, and at the same time make this star The stars continue to exist.

“If a star with an expanded outer layer travels along a very narrow orbit, when it is close enough to the black hole, but not too close, the black hole will strip off some matter and not Will tear the entire star.” said Benjamin Shappee, an astronomer at the University of Hawaii Institute of Astronomy. “In this case, this huge star will return again and again until it is exhausted.”

It is not clear how long this status quo of stars and black holes has lasted, so It is difficult to calculate how long this star can survive. But the research team has predicted that the next two flashes will occur in April and August this year, and the researchers plan to make more observations.

This is an extremely rare opportunity to understand the mass accretion of supermassive black holes.

Ohio State University astronomer Kris Stanek said: “In general, we really want to understand the nature of these black holes and how they grow.” “Accurate The ability to predict when the next event will occur allows us to obtain data that was otherwise unavailable, and we have already gained something.” (Chenchen)