Expanding black hole | What is the size of a black hole?

It's easy to forget, so remember: there is a supermassive black hole in the center of the Milky Way, the galaxy of the Earth. This is not so strange in itself, as astronomers believe that supermassive black holes reside in the center of almost all galaxies. But something is happening with the black hole of the Milky Way, also known as Sagittarius A * or Sgr A *, it's unexpected: it's starting to get more hungry.

"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 latest research, in a press release. "It's usually a rather quiet black hole and wimpy in a diet.We do not know what's driving this great treat."

Ghez and his team have been studying Sagittarius A * for years. They came to their conclusion after analyzing more than 13,000 observations of the black hole collected on 133 nights in early 2003. The photos came from two of the world's elite observatories, some from the WM The Keck Observatory in Hawaii and other people gathered in the very large telescope of the Southern European Observatory in Chile.

Looking at the sightings recently, they noticed that on May 13, the area near the infamous "point of no return" black hole – where the gravitational attraction is so strong that no matter the light, even the light, can escape – was "twice as bright as the next brightest observation".

Combined with two other size changes in 2019, Ghez claims that seeing a Sagittarius A * fluctuate in such a short time is "unprecedented".

At a certain level, scientists know what causes brightness. This is the same type of brightness as in this region, coming from the radiation of gas and dust falling into the black hole. But the expansion of this phenomenon remains a mystery. Was it a punctual growth spurt, something that will continue, or just a single anomaly that will relapse?

"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, "says Mark Morris, professor of physics and astronomy at UCLA and co-author of the journal.

Scientists have considered an idea: to turn to the neighbors of the black hole. Sgr A * has many stars in orbit and gas clouds. One of these stars is known as S0-2, about 10 to 15 times the size of the Earth's sun and gravitates around the black hole as do the planets in our solar system. During the summer of 2018, a large amount of gas was sent to the black hole this year.

"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, "says 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."

There is also a theory regarding the G2 spatial quirk, which according to scientists is probably a pair of binary stars. G2 approached the black hole in 2014, and Sgr A * may have removed the outer layer of G2 and scientists are just seeing it now. And then, there is a third theory, which examines the timing of the disappearance of large asteroids that have been drawn into its gravitational range.

The results of the team were published in Letters from the Astrophysical Journal, the last in a year of discovery of black holes. Back in April, the scientists were finally able to establish a physical proof of their existence on a new historical photo.