Roughly every 114 days, roughly like an hour, a galaxy 570 million light-years away shines like fireworks. Since at least 2014 our observatories have recorded this strange behavior. Now, astronomers put the pieces together to find out why.
At the center of the spiral galaxy, called ESO 253-G003, a supermassive black hole orbits a star every 114 days close enough to smudge some of its material, causing a bright glow of light. Multiple wavelengths. After that, it moves away, and continues to survive again at its next near proximity.
Because of the regularity of the flares, astronomers have called the galaxy “Old Faithful,” such as Geyser in Yellowstone National Park.
“These are the most anticipated and repeated multi-wavelength flares that we have seen from the core of the Galaxy, and they give us a unique opportunity to study this ancient believer outside of the galaxy in detail,” The study’s first author, astronomer Anna Payne, said From the University of Hawaii at Manoa.
“We think that a supermassive black hole at the center of the galaxy is causing explosions because it partially consumes a giant star orbiting it.”
The flares were first detected in November of 2014, and were captured by the All-Sky Automated Scan of Supernovae (ASAS-SN). At the time, astronomers believed that the brightness was a supernova occurring in ESO 253-G003.
But in 2020, when Payne was looking at ASAS-SN data on ESO 253-G003, she found another glow from the same site. And another. And another.
In total, it identified 17 burners, spaced approximately 114 days apart. Then she and her team predicted that the galaxy would erupt again on May 17, September 7, and December 26 of 2020 – and they were right.
They named the repeated ignition ASASSN-14ko, and these accurate predictions meant they were able to take new and more detailed observations of the May flare using NASA’s powerful TESS telescope. Previous observations from other tools also provided data over a range of wavelengths.
“TESS provided a very comprehensive picture of this particular flare, but due to the way the mission portrays the sky, it can’t notice them all,” Astronomer Patrick Vallely said From The Ohio State University. “ASAS-SN collects fewer details on individual blasts, but provides a longer baseline, which is important in this case. The two questionnaires complement each other.”
But the supernova ignites only once, and then it fades, since such an event destroys the original star; So whatever the cause of the flash of light in the UV and X-ray wavelengths must be something else.
A supermassive black hole emitting regular flares as it snacks on a star orbiting around it no one has heard of – one of which was identified last year, in a nine-hour ignition schedule – but the case wasn’t that simple with ESO 253-G003.
This is because ESO 253-G003 are actually two galaxies in the final stages of consolidation, which means that there should be two superfluous galaxies. black holes In the middle of it.
Recent research has shown that two supermassive interacting black holes can cause repeated ignition, but objects in the center of ESO 253-G003 are thought to be too far away to react in this way.
Another possibility has been raised: a star smashing through a cumulative disk of material orbiting and feeding a black hole. This should have been ruled out as well. When the star collided with the disk at different locations and angles, the shapes of the flares should have been different – but observations showed that the flares from ESO 253-G003 were very identical.
A third possibility is the frequent partial perturbation of the tides, in which a larger massive body repeatedly strips material from a smaller orbital object.
If the star was in an eccentric orbit for 114 days around the black hole, its close proximity, or perihelion, could see it deflected close enough to strip off the material before it is hurtling away again.
When this material hits the accretion disk, it causes a glow. This is what appears to be happening.
With this scenario in mind, the team analyzed the observations. They analyzed the light curve for each flare, and also compared it with other known tidal disturbance events of the black hole. They determined that the star was most likely orbiting a supermassive black hole of 78 million solar masses.
On each approach, the star would lose about 0.3% of the Sun’s mass – about three planets – in front of the black hole that would be enough to cause the observed flares while still allowing the star to live.
“If a giant star with a bulging shell wanders close, but not very close, in a very long orbit, then a black hole can steal some external material without tearing the star apart.” Astronomer Benjamin Shabi said From the University of Hawaii Institute of Astronomy. “In this case, the giant star will keep coming back again and again until the star is exhausted.”
It is not clear how long the star and the black hole lasted to maintain this dance, making it difficult to calculate how long the star remained. But the team has anticipated when the next two flares are expected – in April and August of this year – and have plans to take more notes.
It represents an extremely rare opportunity to understand the massive buildup of a black hole.
“In general, we really want to understand the properties of these black holes and how they grow,” Astronomer Chris Stanek said From The Ohio State University. “Being able to predict exactly the timing of the next episode allows us to take data that we couldn’t otherwise take, and we’re actually taking such data.”
The research was presented in The 237th meeting of the American Astronomical Society. It will also be submitted to The Astrophysical Journal, And available at arXiv.