Scientists have been amazed by “strange objects” discovered near the supermassive black hole at the centre of the Milky Way.
Astronomers from UCLA’s Galactic Centre Orbits Initiative described the weird objects in a paper published in the academic journal Nature.
“These objects look like gas and behave like stars,” said the paper’s co-author Professor Andrea Ghez.
According to the astronomers’ observations, the objects look compact most of the time.
However, when their orbits – which range from 100 to 1,000 years – bring them closest to the black hole they bizarrely stretch out under its gravity.
Professor Ghez’s research group first identified an unusual object at the centre of the Milky Way back in 2005. This discovery was named G1.
Seven years later, astronomers in Germany discovered another bizarre object, which became known as G2, in the centre of the galaxy.
When G2 made a close approach to the supermassive black hole in 2014 it again displayed a bizarre stretching behaviour.
Professor Ghez and her team of researchers suspect that G2 was once two distinct stars that had been orbiting the black hole in tandem.
These stars eventually merged into one single extremely large star which is cloaked in unusually thick gas and dust.
“At the time of closest approach, G2 had a really strange signature,” Professor Ghez said.
“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.”
Four more of the so-called G objects have been discovered by Professor Ghez’s team, their orbits have been plotted, and the objects themselves have – perhaps not very creatively – been named G3, G4, G5 and G6.
“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,” said co-author Professor Mark Morris.
“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,” Professor Morris added.
According to Professor Ghez, all six objects may once have been binary stars that merged because of the gravity of the supermassive black hole.
“Mergers of stars may be happening in the universe more often than we thought, and likely are quite common,” she said.
“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.”