The middle of our galaxy makes for a stunning desktop background – but what, exactly, is going on in this image?

This composite image is an oldie, but it's a goodie. It was released back in 2009 in celebration of the International Year of Astronomy. At the time, it was the most detailed and most colorful image of the center of our galaxy ever assembled, a combination of near-infrared, infrared and X-ray images acquired by the Hubble Space Telescope, Spitzer Space Telescope and Chandra X-ray Observatory, respectively. You can explore in great detail in the high-res version featured here.

I bring it to your attention now because, for as many times as I've seen this image, I've never seen it annotated. There's obviously a lot going on in this image, and beautiful though it may be, it would be helpful to know where one might find, say, the black hole that it presumably contains.


The above image, which I recently happened upon in a backdated NASA APOD post, serves as a helpful guide to the star fields, star clusters, gaseous filaments, supernova remnants and the energetic surroundings of the black hole thought to exist at the heart of the Milky Way (that would be the location labelled "Sagittarius A," where a supermassive black hole four-million times as massive as the Sun resides).



h/t Dave!