Cosmic fireworks: Scientists unveil the enigma behind explosive black hole phenomena
A Northwestern University-led team of researchers has shed light on a supermassive black hole’s “disco ball-style” show.
A team of astrophysicists has lifted the lid on an extraordinary, unpredictable “fireworks” display that is being put on each day by the supermassive black hole at the center of the Milky Way, our home galaxy.
“Disco ball-style light show”
Known as Sagittarius A*, the black hole is located some 27,000 light-years away, and has a mass four million times that of our Sun - hence its designation as ‘supermassive’.
First imaged by astronomers in early 2022, Sagittarius A* has a diameter of around 37 million miles - a little over a third of the distance that separates the Earth from the Sun.
And according to a press release posted on the website of the James Webb Space Telescope (JWST) earlier this week, this huge black hole “appears to be having a party, complete with a disco ball-style light show”.
“Our black hole is unique”
A $10 billion telescope launched into space in December 2021, the JWST has played a central role in the new research, whose findings were published in The Astrophysical Journal of Letters on Tuesday.
Led by Northwestern University’s professor Farhad Yusef-Zadeh, the team of astrophysicists used the JWST’s near infrared camera (NIRCam) to observe what appears to be a “random”, ongoing series of small and large flares erupting in the area surrounding Sagittarius A*’s event horizon - the threshold beyond which nothing can escape a black hole’s gravitational pull.
“Sagittarius A* was more active than he [Yusef-Zadeh] anticipated,” reads a statement published on Tuesday by Northwestern University, which is based in Evanston, Illinois. “Simply put: the observations revealed ongoing fireworks of various brightness and durations.”
The news release adds: “While some flares are faint flickers, lasting mere seconds, other flares are blindingly bright eruptions”.
In all, Northwestern University says, five to six major flares were observed each day, interspersed with a larger number of small eruptions.
Speaking to the university’s website, Yusef-Zadeh said: “Flares are expected to happen in essentially all supermassive black holes, but our black hole is unique. It is always bubbling with activity and never seems to reach a steady state.”
He went on to explain: “In our data, we saw constantly changing, bubbling brightness. And then boom! A big burst of brightness suddenly popped up. Then, it calmed down again.
“We couldn’t find a pattern in this activity. It appears to be random. The activity profile of the black hole was new and exciting every time that we looked at it.”
Where exactly are the Sagittarius A* flares happening?
The flares emitted by Sagittarius A* are taking place on what’s known as the black hole’s “accretion disk”.
Per a definition provided by NASA, the U.S. federal space agency, an accretion disk is a “hot, bright, rapidly spinning disk” that is made up of gas and matter orbiting a black hole.
What is causing the “random” flares in Sagittarius A*s accretion disk?
According to Yusef-Zadeh, the smaller flares may be being caused by minor disturbances in the accretion disk, leading to the compression of high-temperature, electrically-charged gas.
“It’s similar to how the sun’s magnetic field gathers together, compresses and then erupts a solar flare,” he told the Northwestern University website.
Meanwhile, the larger flares might be the result of high-speed collisions between magnetic fields, Yusef-Zadeh says.
What’s the next step for the Sagittarius A* researchers?
As explained in the astrophysicists’ paper in The Astrophysical Journal of Letters, the observation of Sagittarius A*’s light show were carried out for a total of 48 hours in 2023 and 2024, across several stints. No single observation lasted for longer than 10 hours.
Now, the team wants to carry out longer observations, lasting for up to 24 hours at a time.
Speaking to the U.S. media outlet NPR, the astrophysicist Moiya McTier explained that continued study of the Sagittarius A* flares can help to uncover new information about the workings of black holes.
“These flares can also give us insight into the magnetic activity of black holes and not just their mass or gravity activity,” McTier said.
“Black holes are still, at their core, a mystery. We know that they are big dense objects and that they attract other things to them through gravity, but we haven’t gotten close to a black hole.”
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