Click for original image.

Cool image time! The picture above, cropped and reduced to post here, was released yesterday and uses archival infrared data from the now retired Spitzer Space telescope to highlight the dust found within the Andromeda galaxy, about two million light years away.

Spitzer’s infrared view was similar to Webb’s but at a far lower resolution. In the picture above the red indicates cool dust.

By separating these wavelengths and looking at the dust alone, astronomers can see the galaxy’s “skeleton” — places where gas has coalesced and cooled, sometimes forming dust, creating conditions for stars to form. This view of Andromeda revealed a few surprises. For instance, although it is a spiral galaxy like the Milky Way, Andromeda is dominated by a large dust ring rather than distinct arms circling its center. The images also revealed a secondary hole in one portion of the ring where a dwarf galaxy passed through.

The data also suggested that the dust is flowing at a very steady rate into Andromeda’s central black hole. According to computer simulations, this steady rate would explain why the supermassive black holes at the center of both Andromeda and the Milky Way are relative inactive. If the dust fell in clumps rather than a steady flow, both black holes would exhibit bursts of high activity, similar to active galactic centers.

A side note for anyone wishing to star-gaze: Andromeda is actually the largest visible galaxy in the night sky, about six times with width of the full Moon. If you can get to a very dark-sky location, get your eyes very dark-adapted, and you know where to look, you can actually see it with the naked eye. I did this once at a star party, helped by a bunch of amateur astronomers. The galaxy is very faint, and it helps to use binoculars to help locate it, but once identified its size in the sky truly is breath-taking.