Anyone would think that astronomers are used to seeing everything. However, every now and then they come across a measurement whose magnitude defies all logic known to man. One of the latest events that has left them completely stunned is the most powerful and prolonged flash ever recorded in the history of astronomy. Astronomers in California managed to record a flare that shone with the fury of 10 million suns.
It came from nothing less than a supermassive black hole located at the center of a distant galaxy. Although the event occurred 10 billion light-years ago, it has only now reached planet Earth. This means that the light we are recording today was emitted when the universe was only about 6 billion years old—in other words, it was still in its infancy. Although this may not seem like a big deal to the average person, for astronomers it is an event that allows us to see what the universe was like in its earliest days.
Detecting the brightest flare in history
This flash of light has been so significant that it has been given its own technical name, AT2021lwx. It has been so powerful that scientists have had to rewrite the black hole physics models that we had created until now.
The discovery was made at the Zwicky Transient Facility (ZTF) in California. The ZTF is a network of telescopes dedicated to scanning the sky for transient objects (i.e., objects that change brightness rapidly, such as exploding stars, unlike planets, which tend to maintain their brightness uniformly). However, the behavior of AT2021lwx was unlike anything they had seen before. While cosmic supernova explosions usually last for weeks, AT2021lwx took three months to reach its maximum brightness. In addition, it has been slowly decaying for more than three years, an extraordinarily long time compared to other types of explosions.
This flare emits a total amount of energy far greater than any supernova. Everything indicates that this flare does not come from a supernova, but from a supermassive black hole.
Super massive black hole * guitar riff *
To put it in context, a black hole is a region of space-time with an extremely dense concentration of mass. The higher the density, the greater the gravity, so its gravity is so intense that not even light can escape its event horizon. Aside from being a great song by Muse released in 2006, a Super Massive Black Hole is the largest version of this type of black hole—like when you order the largest Vanilla Ice Coffee at McDonald’s.
We still don’t know much about black holes, but they are believed to exist at the center of virtually all large galaxies (including our Milky Way). Black holes don’t shine; what they do emit is the light from matter that is about to fall into them. This matter forms a structure called an “accretion disk,” a whirlpool of gas and dust that spins violently around the black hole. The friction between the layers of material heats it to millions of degrees Celsius. This accretion disk is actually the engine of the flares we observe.
What intrigues astronomers is this: what exactly fell into that black hole to create a flare of such magnitude? Did it absorb a planet like Alderaan from the Star Wars universe?
For now, the most obvious hypothesis is that this is a tidal disruption event (TDE). When a star gets too close to a black hole, the difference between the gravitational force on the side closest to the star and the side furthest away completely tears it apart. This process is popularly known as “spaghettification,” which releases a burst of energy.