At the heart of the Milky Way, there's a monster black hole with a mass 4 million times that of the sun, Sagittarius A* (Sgr A*). In the last decade, scientists looking in the black hole's cosmic neighborhood saw two peculiar objects, which seemed to be orbiting the black hole. They were dubbed G1 and G2.
The nature of these so-called "G sources" is controversial. Some astronomers believe they're gas clouds, others contend they look more like strange stars shrouded in dust. In a new study, astronomers reveal they have detected four more of these mysterious objects which look very similar to G1 and G2 -- and suggest they are members of a new class of cosmic phenomena.
Using near-infrared data collected over the last 13 years by the Osiris imager, installed at the W.M. Keck Observatory in Hawaii, the team were able to study the mysterious objects in greater detail. And they had a good template to work from -- both G1 and G2 have been studied fairly intensely and G2, in particular, has enraptured astronomers in the past.
In 2014, astronomers observing G2 watched on as it barreled directly towards Sgr A*. Astronomers predicted G2 was a gas cloud and so it would offer the massive black hole a snack -- as it approached it would be ripped apart and gas would fall into the black hole. But... that's not what happened. G2 got perilously close to Sgr A* and survived, prompting a rethink about what it could be.