The center of our galaxy is occupied by an area where at least 10 million stars are enclosed into one parsec (3.25 light-years) of space. At the core, the supermassive black hole (SMBH) known as Sagittarius A* lays, with an overall mass of more than four million Suns.
For years now, astronomers have been attempting to analyze further this area, hoping to understand the immeasurable forces that operate there and the way they impacted the development of our galaxy.
The Objects Were Not Yet Labeled
After numerous assays, the researchers have discovered a series of stars that rotate at a very close distance to Sagittarius A*; these stars have been used to test Einstein’s Theory of General Relativity. And not long ago, a team of scientists from UCLA’s Galactic Center Orbits Initiative has found a bunch of intricate objects that also rotate around the SMBH. These cosmic bodies are similar to some clouds of gas, but their actions are that of stars, depending on how close they are located in their axis to the black hole.
The research that details the discoveries, which recently was published in the journal Nature, was conducted by Dr. Anna Ciurlo from the University of California, Los Angeles (UCLA).
The team’s work has been based on about 15 years of research that have detected more and more of these cosmic bodies close to the core of our galaxy. The first object, known as G1, was identified back in 2005. This was followed by the discovery of the second object, G2, in 2012, which made a close approach to the supermassive black hole in 2014.
At first, G1 and G2 were believed to be clouds of gas until they had their closest trajectory to the Sagittarius A* and were not blown off by the black hole’s gravitational pull, which is what usually happens to gas clouds when they get close to a black hole.
Professor Andrea Ghez, one of the astronomers who discovered G2, explained: “At the time of closest approach, G2 had a really strange signature. We had seen it before, but it didn’t look too peculiar until it got close to the black hole and became elongated, and much of its gas was torn apart. It went from being a pretty innocuous object when it was far from the black hole to one that was really stretched out and distorted at its closest approach and lost its outer shell, and now it’s getting more compact again.”
More Objects Were Identified
Back in 2018, Dr. Cuirlo and an international team of researchers, including Prof. Ghez, used 12 years of information collected by the W.M. Keck Observatory and adaptive optics technology to detect three more similar objects, namely G3, G4, and G5, close to the galaxy’s center. Since 2018, six more cosmic bodies of this kind have been detected in this particular region.
Mark Morris, a UCLA professor of physics and astronomy and a co-author on the study, explained: “One of the things that has gotten everyone excited about the G objects is that the stuff that gets pulled off of them by tidal forces as they sweep by the central black hole must inevitably fall into the black hole,” he said.
“When that happens, it might be able to produce an impressive fireworks show since the material eaten by the black hole will heat up and emit copious radiation before it disappears across the event horizon.”
While analyzing the Milky Way‘s core area, the research team has reported the finding of six objects until now. Even so, they are observed that while G1 and G2 have incredibly similar orbits, the other four cosmic bodies’ trajectory is a lot different. This certainly raises the question of whether all six bodies are a similar group of objects, or G1 and G2 are misfits.
Ghez and her colleagues suggest that all six cosmic objects were binary stars that combined due to the supermassive black hole’s gravitational powers. This operation would have taken more than one million years to reach an end and could suggest that binary star mergers are, in fact, rather common.
Ghez explained: “Black holes may be driving binary stars to merge. It’s possible that many of the stars we’ve been watching and not understanding may be the end product of mergers that are calm now. We are learning how galaxies and black holes evolve. The way binary stars interact with each other and with the black hole is very different from how single stars interact with other single stars and with the black hole.”