Astronomers said Thursday they have seen a hot gas bubble spinning clockwise around the black hole at the center of our galaxy at “staggering” speeds. The detection of the bubble, which survived only a few hours, will hopefully provide insight into how these invisible, insatiable, galactic monsters work.
Thelurks in the center of the Milky Way, some 27,000 light-years from Earth, and its massive gravitational pull gives our own galaxy its characteristic vortex.
The first-ever image of Sagittarius A* was unveiled in May by the Event Horizon Telescope Collaboration, which connects radio dishes around the world to detect light disappearing into the mouths of black holes.
One such dish, the ALMA radio telescope in the Andes Mountains in Chile, picked up something “quite puzzling” in the Sagittarius A* data, said Maciek Wielgus, an astrophysicist at Germany’s Max Planck Institute for Radio Astronomy.
Just minutes before ALMA’s radio data collection began, the Chandra Space Telescope observed a “huge spike” in X-rays, Wielgus told AFP.
This burst of energy, thought to be similar to solar flares on the sun, sent a hot gas bubble around the black hole, according to a new study published in the journal Astronomy and Astrophysics.
The gas bubble, also known as a hotspot, had an orbit similar to Mercury’s journey around the sun, said the study’s lead author, Wielgus.
But while Mercury takes 88 days to make that journey, the bubble did it in just 70 minutes. That means it traveled at about 30 percent of the speed of light.
“So it’s an absolute, ridiculously fast-spinning bubble,” Wielgus said, calling it “stunning.”
The scientists were able to track the bubble through their data for about an hour and a half — it was unlikely to have survived more than a few orbits before being destroyed.
Wielgus said the sighting supported a theory known as MAD. “MAD like crazy, but also MAD like magnetically arrested disks,” he said.
The phenomenon is thought to occur when there is such a strong magnetic field at the mouth of a black hole that keeps the material from being sucked in.
But the matter continues to pile up, building up into a “flux burst,” Wielgus said, interrupting the magnetic fields and causing a burst of energy.
By learning how these magnetic fields work, scientists hope to build a model of the forces that control black holes, which remain shrouded in mystery.
Magnetic fields can also help indicate how fast black holes are spinning – which may be especially interesting for Sagittarius A*.
Although Sagittarius A* has four million times the mass of our sun, it only shines with the power of about 100 suns, “which is extremely uninteresting for a supermassive black hole,” Wielgus said.
“It’s the faintest supermassive black hole we’ve seen in the universe — we’ve only seen it because it’s very close to us.”
But it’s probably a good thing that our galaxy has a “starved black hole” at its center, Wielgus said.
“Living next to a quasar,” which can shine with the power of billions of suns, “would be terrible,” he added.
By definition, black holes cannot be observed directly because nothing, not even light, can escape the crushing inner force of their gigantic gravity.
But their presence can be detected indirectly by observing the effects of that gravity on the orbits of nearby stars and by the radiation emitted across the electromagnetic spectrum by material heated to extreme temperatures as it spins into a rapidly rotating “accretion disk”. sucked and then into the hole itself.
A major goal of the new James Webb Space Telescope is to help astronomers chart the formation and growth of such black holes in the aftermath of the Big Bang.
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