Strange Objects Found at The Galactic Center Are Like Nothing Else in The Milky Way

There’s something really weird in the center of the Milky Way.

The proximity of a supermassive black hole is a pretty strange place to start, but in 2020 astronomers discovered six objects orbiting Sagittarius A* that are unlike anything in the galaxy. They’re so special that they’ve been assigned a whole new class, which astronomers call G-objects.

The two original objects – dubbed G1 and G2 – first caught the attention of astronomers almost two decades ago, and their orbits and strange properties have continued to deteriorate over the years. They looked like giant clouds of gas, 100 AU in diameter, that expanded with the emission spectra of gas and dust as they got closer to the black hole.

But G1 and G2 did not behave like gas clouds.”These objects look like gas but behave like stars,” explained physicist and astronomer Andrea Ghez of the University of California, Los Angeles in 2020.Ghez and his colleagues have been exploring the center of the galaxy for more than 20 years. Using this data, a team of astronomers led by UCLA astronomer Anna Ciurlo identified four other similar objects: G3, G4, G5, and G6.They are on completely different orbits than G1 and G2 (see figure above); Together, the G objects have orbital periods of 170 to 1600 years.

It’s not entirely clear what they are, but G2’s emergence unharmed from periapsis in 2014 — the point in its orbit closest to the black hole — was an important clue, according to Ghez.

“On its closest approach, G2 had a really weird signature,” he said.”We’ve seen this before, but it didn’t look too weird until it got close to the black hole, expanded, and most of the gas was removed. It wasn’t a pretty benign object anymore when you removed it.” the black hole into an object that on closest approach really got stretched and distorted and lost its outer shell, and now it’s getting bigger

G2 was previously believed to be a cloud of hydrogen gas, which is ruptured and absorbed by Sgr A, creating supermassive fireworks as the black hole accretes. The fact that nothing happened was later referred to as “cosmic failure”

Astronomers believe the answer lies in massive binaries. Most of the time these twin stars, which are in a common orbit, spend their free time making friends. But sometimes, as with colliding black hole binaries, they can collide and form a giant star.

When this happens, they create a huge cloud of dust and gas that surrounds the new star for about a million years after the collision.”Something must have held [G2] together and allowed it to survive the black hole encounter,” Ciurlo added. “This is evidence for a stellar object in G2.”And the other five? Well, it might as well be binary star mergers.Most of the stars at the center of the galaxy are very massive and most of them are binary star systems. And the extreme gravitational forces acting around Sgr A may be enough to destabilize their binary orbits fairly frequently.

“Star mergers may occur more frequently in the Universe than we thought, and are probably quite common,” Ghez said.

“Black holes can cause binary star mergers. It’s possible that many of the stars we’ve observed that we don’t understand are the end products of mergers that are now dormant.

“We learn how galaxies and black holes evolve. The way binaries interact with each other and with a black hole is very different from the way single stars interact with other single stars and a black hole.

”TheG-Objects seem to have a lot in common, whatever they may be, and expanding the data set may only provide more information to solve the mystery. However, there is still a lot to discover. Like the mysterious Sgr A* fireworks that have also been spotted.

Was this a delayed reaction of G2 periapsis? After all, wasn’t the cosmic fiasco so effervescent? Maybe we’ll just look at this weird little corner of supermassive space to see what happens next…