The gigantic black hole in the center of our Milky Way is currently treating itself to an unusually rich meal. This is what astronomers conclude from a sudden burst of brightness of the mass monster: it shines brighter than ever since observations began. Photo: ESO/Gravity Consortium/L. Calcada
The black hole in the center of the Milky Way normally behaves rather quietly. In spring, it suddenly shone twice as brightly as usual. Researchers can only speculate about the cause so far.
Los Angeles – The giant black hole at the center of our Milky Way is currently treating itself to an unusually rich meal. This is what astronomers conclude from a sudden burst of brightness of the mass monster: It shines brighter than ever since observations began. "We haven’t seen anything like it in the 24 years we’ve been studying the supermassive black hole," reported Andrea Ghez of the University of California at Los Angeles.
The researchers present their observations in the journal The Astrophysical Journal Letters. ÜThey are still puzzling over the cause of the sudden outburst.
Mass of four billion suns
Like most galaxies, the Milky Way has an extremely massive black hole at its center. It combines the mass of about four million suns. Black holes themselves are not visible, but when matter falls into their gravitational vortex, it heats up and glows brightly before disappearing, never to be seen again, behind the so-called event horizon.
Some supermassive black holes produce more radiation in this way than the entire galaxy in which they are located.
Is instellar gas flowing into the black hole?
Not so the black hole in the center of our Milky Way. "It’s usually a pretty quiet, faint black hole on a diet," Ghez explained. The researchers had analyzed about 13,000 measurements from 133 nights since 2003.
On 13. In May 2019, the black hole suddenly shone twice as brightly as in the brightest of the remaining images. "The big question is whether the black hole is entering a new phase," Ghez’s colleague Mark Morris emphasized. This could mean, for example, that the amount of interstellar gas flowing into the black hole is increasing for a longer period of time.
Other possible explanations are, for example, large asteroids that were pulled into the black hole, or individual clumps of interstellar gas that could have caused the sudden fireworks.
No danger for the earth
Another possible cause could be the star S0-2, which orbits the central black hole on a path that takes it very close to the event horizon. It may have flung gas toward the black hole during its recent closest approach in summer 2018, which is now falling into the mass monster.
ÄThe same could be true of the celestial object known as G2, which is believed to be a binary star. It came close to the black hole in 2014 and may have lost its outer shell in the process, the astronomers argue.
Which cause is responsible for the sudden outbreak of the black hole, only further observations will be able to show. Scientists emphasize that there is no danger to Earth. The mass monster at the center of the Milky Way is 26,000 light-years from Earth, they said, and its radiation would have to be at least 10 billion times as strong as observed to play a role in life on Earth.
Most massive objects in the universe
Black holes are one of the predictions of general relativity, which Einstein proposed about a century ago. In them the mass of several to several billion suns is compressed to one point.
Due to the immense gravitation, not even light can escape from the immediate surroundings, hence the name. Black holes, for example, can form when burned-out giant stars collapse under their own weight.
All light is swallowed
A black hole itself is invisible even to the best telescopes. Drawings based on general relativity often show a black circle with a brilliantly bright ring.
The inside of this ring marks the so-called event horizon, which gave the project its name. It is the place on the periphery of a black hole from which light can still escape. So you only take a picture of the bright ring around the black hole.
Black holes suck up matter
Many black holes ingest new matter. But this matter does not fall directly into the black hole. Instead, it collects on an ever faster rotating disk – similar to water flowing out of the bathtub in a whirlpool.
In this so-called accretion disk, the matter becomes millions of degrees hot due to mutual friction and thus shine brightly before disappearing forever in the maw of the gravity monster.