A black hole in the center of our galaxy seems to be more hungry

The huge black hole in the center of our galaxy contains an unusual amount of gas and interstellar dust, and researchers still do not understand why.

"We have never seen anything like it for 24 years as we study the supermassive black hole," said Andrea Ghez, professor of physics and astronomy at UCLA and co-lead author of the research. "It's usually a rather quiet black hole and wimpy in a diet.We do not know what's driving this great treat."

An article on the study, led by the UCLA Galactic Center Group, led by Ghez, is published today in Letters from the Astrophysical Journal.

The researchers analyzed more than 13,000 observations of the black hole made on 133 nights since 2003. The images were collected by the W.M. Keck Observatory in Hawaii and the very large telescope of the Southern European Observatory in Chile. The team discovered that on May 13, the area just outside the "point of no return" black hole (so called because once the material is entered, it can no longer escaping) was twice as bright as the next most brilliant observation.

They also observed significant changes two more nights this year; These three changes were "unprecedented," said Ghez.

The luminosity observed by scientists is due to the radiation of gas and dust falling into the black hole; the results prompted them to ask if it was an extraordinary singular event or a precursor of a significant increase in activity.

"The big question is whether the black hole enters a new phase – for example, if the valve has been raised and the rate of black hole gas has increased for an extended period of time – or if we are coming from see the fireworks with a few unusual gas drops, "said Mark Morris, professor of physics and astronomy at UCLA and co-author of the journal.

The team has continued to observe the region and will try to address this issue based on what they see from new images.

"We want to know how black holes are developing and are affecting the evolution of galaxies and the universe," said Ghez, Lauren B. Leichtman, Arthur E. Levine's chair. astrophysics. "We want to know why the supermassive hole becomes brighter and how it becomes."

The new discoveries are based on observations of the black hole – called Sagittarius A * or Sgr A * – during four nights in April and May at the Keck Observatory. The brightness around the black hole still varies somewhat, but scientists were stunned by extreme variations in brightness during this period, including their May 13 sightings.

"The first image I saw that night, the black hole was so bright that I had initially confused it with the star S0-2 because I had never seen it before. Sagittarius A * also brilliant, "said Tuan Do, researcher at UCLA, lead author of the study. "But it soon became clear that the source had to be the black hole, which was really exciting."

One hypothesis regarding the increase in activity is that when a star called S0-2 approached the black hole very closely during the summer of 2018, she threw a large amount of gas that reached the black hole this year.

Another possibility is a weird object called G2, which is probably a pair of binary stars, which came closest to the black hole in 2014. It is possible that the black hole could have removed the layer G2 external, said Ghez, which could help explain the increase in brightness just outside the black hole.

Morris added that another possibility is that the lightening corresponds to the disappearance of large asteroids that have been dragged into the black hole.

No danger for the Earth

The black hole is about 26,000 light-years away and does not pose a threat to our planet. Do say that the radiation should be 10 billion times brighter than what astronomers have detected to affect life on Earth.

Letters from the Astrophysical Journal The researchers also published a second article written by the researchers, describing speckle holography, a technique that allowed them to extract and use very fuzzy information over 24 years of nearby recorded data. black hole.

The Ghez research team reported on July 25 in the journal Science the most comprehensive test of Einstein's emblematic relativity theory near the black hole. Their conclusion that Einstein's theory passed the test and is correct, at least for the moment, is based on their study of S0-2 in that it creates a complete orbit around the black hole.

Ghez's team studies more than 3,000 stars that revolve around the supermassive black hole. Since 2004, scientists have used a powerful technology that Ghez helped invent, adaptive optics, which corrects the distortion effects of the Earth's atmosphere in real time. But speckle holography has allowed researchers to improve data from the decade before the entry into force of adaptive optics. Reanalysis of data from these years helped the team conclude that they had not seen this level of brightness near the black hole for 24 years.

"It was like operating at LASIK on our first images," said Ghez. "We collected the data to answer a question and accidentally uncovered other exciting scientific discoveries that we had not anticipated."