The image above was just released today from NASA’s Swift spacecraft. This is M31 – otherwise known as the Andromeda Galaxy – located in the direction of the constellation Andromeda, visible in the evening sky at this time of year.
This is the largest and closest spiral galaxy to our own, at some 2.5 million light-years away. If you were on a planet orbiting a star in this galaxy, and could look back our Milky Way galaxy, it’s thought our home galaxy would look a lot like this.
You can see a full-sized version of the image here.
NASA says this the highest-resolution view of a neighboring spiral galaxy ever attained in the ultraviolet.
The Swift satellite has seen about 20,000 ultraviolet sources in M31, especially hot, young stars and dense star clusters, according to Stefan Immler, a research scientist on the Swift team at NASA Goddard Space Flight Center.
Notice the striking difference between the galaxy’s central bulge and its spiral arms. Immler explained the bulge is smoother and redder because it’s full of older and cooler stars. He said few new stars form in the bulge because most of the materials needed to make them have been depleted.
As in our own galaxy, M31’s disk and spiral arms contain most of the gas and dust needed to produce new generations of stars. So you can see clusters of hot, young, blue stars in M31’s disk and arms. Astronomers say this work will let them learn more about star formation in this galaxy.
You’ll find more about this image and the work needed to create it here,
Here’s a chart showing how to see the Andromeda Galaxy now in the night sky. This link goes to September 24 in our daily EarthSky Tonight feature … but you can see the galaxy using this chart anytime in the coming weeks. Tonight is great, in fact, because the moon is close to new and therefore out of the way. Happy hunting!
Deborah Byrd created the EarthSky radio series in 1991 and founded EarthSky.org in 1994. Today, she serves as Editor-in-Chief of this website. She has won a galaxy of awards from the broadcasting and science communities, including having an asteroid named 3505 Byrd in her honor. A science communicator and educator since 1976, Byrd believes in science as a force for good in the world and a vital tool for the 21st century. "Being an EarthSky editor is like hosting a big global party for cool nature-lovers," she says.