Approximately every 114 days, almost like a clock, a galaxy 570 million light-years glows like fireworks. Since at least 2014, our observatories have been registering this strange behavior; now astronomers have put the pieces together to understand why.
At the center of a spiral galaxy called ESO 253-G003, a supermassive black hole is in a star orbit that swings close enough every 114 days for some of its material to slip out, causing a brilliant burst of light multiple lengths of light. the wave. He then moves away, surviving to be eluded again in his next close approach.
Because of the regularity of the eruptions, astronomers have named the galaxy “Old Faithful,” similar to the geyser in Yellowstone National Park.
“These are the most predictable and recurring multiwave eruptions we̵
“We believe that a supermassive black hole in the center of the galaxy creates bursts as it partially engulfs an orbital giant star.”
The flares were first discovered in November 2014, taken from the automated All-Sky supernova study (ASAS-SN). At the time, astronomers believed that the illumination was a supernova found in ESO 253-G003.
But in 2020, when Payne was reviewing ESO 253-G003’s ASAS-SN data, she found another torch from the same location. And another. And another.
In total, it identified 17 missiles with an interval of about 114 days. Then she and her team predicted that the galaxy would explode again on May 17, September 7 and December 26, 2020 – and they were right.
They pointed to the ASASSN-14ko re-explosion, and these accurate predictions meant they were able to make new, more detailed observations of the May outbreak with NASA’s powerful TESS telescope. Previous observations from other instruments have also provided data on a range of wavelengths.
“TESS provided a very in-depth picture of this particular torchlight, but because of the way the mission depicts the sky, it can’t observe them all,” said astronomer Patrick Valley of Ohio State University. “ASAS-SN collects less detail for individual outbreaks, but provides a longer baseline, which was extremely important in this case. The two studies complement each other.”
But a supernova erupts only once, then fades, as such an event destroys the rising star; so whatever caused the eruption of light at optical, ultraviolet, and X-ray wavelengths must be something else.
A supermassive black hole emitting regular eruptions while eating an orbital star is not unheard of – one was identified last year by nine-hour flames, but the case was not so simple with ESO 253-G003.
This is because ESO 253-G003 is actually two galaxies in the final stage of the merger, which means that there must be two supermassive black holes at its center.
Recent research has shown that two interacting supermassive black holes can cause multiple burns, but it is thought that the objects in the center of ESO 253-G003 are too far apart to interact in this way.
Another raised possibility is for a star to crash through an accretion disk of material that rotates around and feeds into one of the black holes. This also had to be ruled out. As the star crashed through the disk at different places and angles, the shapes of its eruptions had to be different – but observations showed that the bursts from ESO 253-G003 were too close.
The third possibility was the repeated partial disturbance of the tides, when a larger massive object repeatedly takes material from a smaller orbital one.
If a star were in an eccentric 114-day orbit around the black hole, its close approach or periastron could see it deviate close enough to take off material before throwing again.
When this material collides with the accretion disk, it causes an eruption. And this seems to be happening.
Given this scenario, the team analyzed the observations. They analyzed the light curve of each eruption and compared them to other known events from the tides of the black hole. And they determined that the star was probably in orbit around a supermassive black hole with 78 million solar masses.
At each closest approach, a star losing about 0.3% of the Sun’s mass – about three Jupiters – to the black hole would be enough to cause the observed bursts, while allowing the star to live.
“If a giant star with a swollen shell wanders close, but not too close, in a very elongated orbit, then the black hole can steal some of the outer material without tearing the entire star.” said astronomer Benjamin Shapi of the Institute of Astronomy at the University of Hawaii. “In that case, the giant star will just come back again and again until the star runs out.”
It is not clear how long the star and the black hole support this dance, which makes it difficult to calculate the time the star stays. But the team predicts when the next two flares should appear – in April and August this year – and plans to make even more observations.
It is an extremely rare opportunity to understand the supermassive increase in the mass of a black hole.
“In general, we really want to understand the properties of these black holes and how they grow,” said astronomer Chris Stanek of Ohio State University. “The ability to predict the exact time of the next episode allows us to take data that we might not otherwise be able to take, and we are already taking it.”
The study was presented at the 237th meeting of the American Astronomical Society. It will also be handed over to The Astrophysical Journal, and is available on arXiv.