For about two hours, a bubble of extremely hot electrons circled the Milky Way’s supermassive black hole at 30 percent the speed of light and then was destroyed.
September 22, 2022
Astronomers have found what appears to be a bubble of hot electrons whirling around Sagittarius A*, the supermassive black hole at the center of the Milky Way, at extraordinary speeds. This strange bubble could help us learn how black holes devour the material around them.
Maciek Wielgus at the Max Planck Institute for Radio Astronomy in Germany and colleagues used the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to observe the area around Sagittarius A* as the black hole emitted a huge X-ray flare. Minutes after the flare, they saw a huge “hot spot” of radiation, most likely composed of electrons heated to billions of degrees, circling the black hole in an orbit roughly Mercury’s distance from the sun.
Mercury takes 88 days to orbit the sun, while this bubble only took about 70 minutes to go around Sagittarius A*, which means it was traveling at 30% of the speed of light. The researchers were only able to see it for two orbits before it faded from view, either destroyed or no longer emitting light at the wavelengths that ALMA can see.
“The bubble can’t be too small, because a small bubble wouldn’t go away that quickly,” says Wielgus. “It’s a huge bubble, it’s not a tiny guy.”
From observations of just two orbits, the researchers were able to determine that the magnetic fields affecting the bubble appear to be aligned as we would expect them to be based on a model of black holes called the stopped magnetic disk model. “It tells us that maybe our models of these systems really have something to do with reality,” says Wielgus.
The bubble’s orbit also implied that the material immediately surrounding the black hole surrounds it in a path perpendicular to the disk of the galaxy, meaning that from Earth we are looking at it head-on despite being located in the disk, which has been hinted at by earlier observations as well. “We’re on the galactic plane, so it seems like we should be looking at it head-on, but it is what it is,” he says. “Is rare.”
Studying this area in more detail could help us learn more about how black holes gobble up matter and why they throw off massive flares, but we’ll have to do that research from afar.
“The view from this bubble would be a kind of magical kaleidoscope: you’d look in one direction and see something from a totally different direction because of the light bending in the black hole’s gravity, but you’d have to be very resilient to survive the many billions of degrees,” says Wielgus. “If you were to magically materialize inside this bubble, you would disappear just as quickly.”
Magazine Reference: astronomy and astrophysics, DOI: 10.1051/0004-6361/202244493
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