Last February, astronomers at the Zwicky Transient Facility in California spotted a bright flash of light. The vivid brilliance, later named AT 2022cmc, sparked endless questions.
While such flashes aren’t exactly new to scientists — astronomers have seen tons of these flashes from deep space before — this one in particular existed in a category of its own. Emanating about 8.5 billion light-years away, it seemed to emit more light than 1,000 trillion suns combined. The human mind can hardly comprehend such a quantity, much less such a quantity of…suns.
Since the spectacular discovery of this glow, scientists around the world have started trying to decode where, why and even how. the lightning event could have happened. And a pair of papers published Wednesday in the journals Nature and Nature Astronomy conclude that Zwicky picked up the signal for a particularly extreme “tidal disturbance event” or TDE.
In other words, the team behind these studies believe that the flash originated from a jet of matter pouring out from inside a supermassive black hole, traveling at supersonic speeds and aimed directly at our planet.
“We found that the speed of the jet is 99.99% the speed of light,” said Matteo Lucchini, a researcher at MIT’s Kavli Institute for Astrophysics and Space Research and co-author of the study. published in Nature Astronomy, in a press release.
When black hole pioneer John Wheeler presented the idea of the TDE-jet combo in 1971, he described it as “a tube of toothpaste squeezed down the middle”, causing it to “eject matter from the two ends”. Only about 1% of TDEs produce these ultrafast or relativistic jets of plasma and radiation shooting out from its two poles.
This jet, if the team is correct about its existence, would represent the most distant tidal disturbance event ever detected. But what strikes above all is its luminosity. It’s because the brighter the object, the easier it is to get information from it.
A total of 21 telescopes around the world collected observational data on the jet through a wide range of light types, from radio waves to high-energy gamma rays. All of this information was then compared to data from known cosmic events ranging from neutron stars to kilonovae, but the only possibility that provided a solid match was a jet TDE pointing straight at us.
To that end, researchers believe it appears abnormally bright from our vantage point on Earth for two reasons.
First, the jet black hole is likely to devour a nearby star, releasing a substantial amount of energy and emitting a ton of light during its feast. As MIT study co-author Dheeraj “DJ” Pasham puts it, the jet is extremely active and in a “hyper-feeding frenzy.”
“It’s probably swallowing the star at the rate of half the mass of the sun per year,” Pasham said in a statement. “A lot of this tidal disturbance happens very early on, and we were able to capture this event early on, a week after the black hole started feeding on the star.”
But the second – and the most fascinating, in our opinion – is due to an effect called “Doppler amplification”.
What is Doppler amplification?
Basically, the Doppler effect refers to how sound waves, light waves, and any other type of wave change as the thing making those waves moves toward or away from you.
Think about what happens when a car playing music passes in front of your house. As it gets further away, the sound not only becomes less pronounced, but it often changes in pitch. This is because the sound waves kind of stretch out, causing your brain to recognize them as being at a lower pitch.
The Doppler effect also occurs with light waves – often referred to by astronomers as redshift when it comes to bright galaxies and stars moving away from our planet.
As these elements move away, the light waves they emanate stretch out, changing from tighter bluish to more relaxed reds. Eventually, they even walk in infrared waters, invisible to human eyes and standard optical machinery – which is why NASA’s James Webb Space Telescope is so important. It can capture those super-stretched wavelengths present in the deep, dark universe.
But in the case of AT 2022cmc’s relativistic jet, the light is pointing towards us, so it doesn’t get redder or softer with distance. It becomes increasingly luminescent as its photons approach our telescopes, further enhanced by the fact that they spit with enough vigor to almost match the speed of light.
“Because the relativistic jet is pointing towards us, it makes the event much brighter than it would otherwise appear and visible over a wider stretch of the electromagnetic spectrum,” said Giorgos Leloudas, astronomer at DTU Space in Denmark and co -author of the study in nature.
Typically, abnormally bright bursts of light like this tend to come from what are called gamma ray bursts. Gamma-ray bursts are also beautiful jets, though they are made up of X-ray emissions spewed out by massive stars as their stellar bodies collapse. Due to their scintillating nature, these phenomena tend to populate the pantheon of astronomy. Last month, in fact, scientists were stunned by a powerful gamma-ray burst coming from some 2.4 billion light-years away in the universe. It is literally called BOAT – the brightest of all time.
But AT 2022cmc, after further speculation, was definitely not a gamma-ray burst.
“This particular event was 100 times stronger than the strongest afterglow from the gamma-ray burst,” Pasham said. “It was something extraordinary.”
Lo and behold, after weeks of data mining and removing all astronomical observation stops with X-ray, radio, optical and UV telescopes, the team concluded that AT 2022cmc must have originated from the magnetic vortex of debris from a black hole. It must be a tidal disturbance event, pigmented by the Doppler effect. If so, that makes it the fourth Doppler-boosted TDE ever found and the first Doppler-boosted event in general seen since 2011. It is also the first TDE found using an optical survey of the sky.
Scientists were also able to use the full spectrum of AT 2022cmc observations to help determine its temperature and distance.
“Our spectrum told us the source was hot: around 30,000 degrees, which is typical for a TDE,” said Matt Nicholl, associate professor at the University of Birmingham. “But we also saw some absorption of light by the galaxy where this event occurred. These absorption lines were strongly shifted to redder wavelengths, telling us that this galaxy was much farther away than intended.”
Remarkably, the center of this distant galaxy is not yet visible as it is swept away by the brightness of AT 2022 cmc, but when it eventually fades, the source galaxy can become observable with the James Webb Telescope.
In the meantime, researchers will continue to scan the skies for the exotic and poorly understood jet-powered TDE.
“We expect a lot more of these TDEs in the future,” Lucchini said. “So maybe we can say, finally, how exactly black holes launch these extremely powerful jets.”
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