We have known since the late 1990s that our galaxy has a supermassive black hole in its core that is 4.3 million times the mass of our Sun, and is orbited by stars that get as close to this black hole as 970 astronomical units, or roughly 20 times Pluto’s distance from the Sun. This understanding comes the amazing work of UCLA’s Andrea Ghez who created a new way to use the Keck telescopes to take extraordinarily high resolution ground based images of the stars swarming Sag A*. As her team and other astronomers have followed the motions in the inner part of the Milky Way, they have revealed a cluster of young stars with ages measured in millions rather than billions of years. While this team has been able to see individual stars, they have only been able to see the largest stars, and it has been suspected that there is a large population of what are called S-Cluster stars that orbit in this inner region, with the more numerous smaller stars being beyond what our telescopes can see.

Last week this story got one new population of objects, unceremoniously called G objects,  appear to be gas & dust blobs that are getting distorted during their closest passes near Sag A*. These objects can be explained as merged small binary stars, and they exist in numbers consistent with what would be seen in a star cluster with the population of large stars we see as S-cluster stars. This traces out a picture of a young star cluster forming as it plunges for whatever reason into the heart of our galaxy. This system was then dynamically stirred up by the gravity of Sag A* with stars – the massive S stars and the merged binary G objects and all the objects too small for us to see – all sent into chaotic orbits. This is a special moment in time during the short period when these massive stars are alive and easy to see. We have no idea how common this kind of a star cluster plunge takes place, and the science coming out of this is still emerging and is awesome.

And while this is all awesome, the best may be yet to come. The Event Horizon Telescope has unreleased images of Sag A*. Last April the Event Horizon team released their image of the significantly larger M87 SMBH. The smaller Sag A* has been harder to process since the material around it is comparably more obscuring. When that image comes out it will build this picture out in new ways and in new details. 

Learn more about this at:

Astronomers Discover Class Of Strange Objects Near Our Galaxy’s Enormous Black Hole (Keck)