Ladies and gentlemen, allow me to present the best-ever ultraviolet picture (at right) of our galactic neighbor, M31, aka the Andromeda Galaxy.

Taken by NASA’s Swift satellite, which normally scans the skies for far-off gamma-ray bursts, this picture represents a total exposure time of just 24 hours, taken during late spring 2008. It merges 330 images taken by the satellite, showing a region 200,000 light-years wide by 100,000 light-years high (or 100 arcminutes by 50 arcminutes).

The galaxy’s central bulge appears smoother and redder because of the older, cooler stars that reside there, according to Stefan Immler, a research scientist on the Swift team at NASA’s Goddard Space Flight Center. It’s mostly full of old stars because much of the star-making material in the area already has been used up. The disk and spiral arms still have some of the necessary gas and dust to produce stars, just like in our own Milky Way Galaxy, and that’s where the more recent, hotter, bluer stars dwell.

M31 is more than 220,000 light-years across, close to twice as much as the Milky Way. Despite being about 2.5 million light-years away, M31 is so big and bright you can see it unaided on a clear, dark night. Pretty impressive.

I don’t know about you, but I love pictures like this. Being a city-dweller most (well, all) of my life, I appreciate the extra-detailed images in particular, having never seen a vista of countless twinkling stars in real life. I always feel like, as long as NASA takes these pictures and gets them out there, it could never run out of funding. Of course, one never knows when it comes to funding, or NASA.

So how about you? Amazed by awesome Andromeda? Or do you give M31 a mere “meh”?

Related:

Images of Andromeda in our Online Reader Gallery.

Find the Andromeda Galaxy (M31) tonight with our interactive star chart, StarDome

Photo credit: NASA/Swift/Stefan Immler (GSFC) and Erin Grand (UMCP)