The Triangulum Galaxy, writ large

The Triangulum Galaxy, writ large

The Triangulum Galaxy, writ large

Bad Astronomy
The entire universe in blog form
July 11 2011 7:17 AM

The Triangulum Galaxy, writ large

Need a little face-on spiral awesomeness for your Monday morning? Then try this magnificent image of the nearby face-on spiral galaxy M33, aka the Triangulum Galaxy:

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  

Advertisement

[Click to islanduniversalize, or go here to get the cosmic 7900 x 8000 pixel version.]

That not enough for ya? Then try this: Here's a zoomable and pannable version!

You're welcome.

This image is from Davide de Martin, who takes images from professional observatories, reprocesses them, and puts them on his Sky Factory website. M33 is a bit of an odd beast: it's the second-closest spiral galaxy to our own -- at about 3 million years away, it's just a bit farther away than the Andromeda Galaxy -- but it's fainter than you might expect in the sky. That's because it's dinky, less than half the size of our Milky Way, and face-on, which means that small amount of light gets spread out, dimming it.

Advertisement

I've never seen it naked eye (Andromeda is actually pretty easy to spot from a dark site) but I've observed it many times with binoculars and a small telescope. Davide had a bit of an advantage though: this picture is from observations using the 4-meter Mayall telescope at Kitt Peak, a fine instrument indeed. The picture uses mostly "natural" color, adding together blue, green, and red-filtered images.

Also included in that summation is one more image using a filter that only lets though a very specific wavelength of light associated with warm hydrogen. Called Hα, this is given off by gas clouds forming stars, and is shown here as the sharp red color. So wherever you see those blobs of red, stars are forming at a furious rate. And look to the upper left: see that particularly large and bright nebula? That is NGC 604, a monstrous star-forming region that's 1500 light years across or more; it puts our own Orion Nebula to shame. It's one of the largest stellar factories in the Local Group of galaxies; if it were as close as Orion it would be visible in the daytime!

One other thing: the spiral arm to the left and below NGC 604 appears to be sharply defined and almost straight. I'm thinking that's a perspective effect, but the arm itself does appear pretty well-defined in a far-infrared image as well. It's interesting what you find looking at such fine images, and comparing them at different wavelengths.

Advertisement

I had a lot of fun flying over the zoomable image. The red star-forming nebulae come in many shapes and sizes; take a look all the way over on the right for a couple of them that have filaments and arcs; I think the stars inside them are blowing away the gas, sculpting it into eerie and lovely shapes.

There's a lot to see here. Have fun!

Image credit: KPNO, NOAO, AURA, Dr. Philip Massey (Lowell Obs.) - Image processing: Davide De Martin.


Advertisement

Related posts: