Messier 33
Messier 33, the Triangulum Galaxy, is a beautiful large face-on spiral galaxy located in the constellation of Triangulum. Also known as the Pinwheel Galaxy, M33 was first discovered before 1654 by Giovanni Battista Hodierna, and then re-discovered by comet-hunter Charles Messier in 1764. Numerous HII emission nebulae and star-forming regions in M33 are recorded in this image. Hold your mouse cursor over the image to see their identifications. NGC 604 is the largest HII region at lower left. C39 is the largest and brightest globular cluster in M33 at lower right. M33 is part of our local cluster of galaxies, including our own Milky Way Galaxy, M31, and the Magellanic Clouds. This cluster is also part of a much larger super-cluster of galaxies called the Virgo cluster. M33 covers an apparent area of sky larger than the full moon, but it also has a relatively low surface brightness. From a dark-sky site under good conditions, it can be seen by keen-eyed observers without optical aid. It is one of the most distant objects that can be seen with the unaided eye at a distance of 3 million light-years, slightly farther than its much brighter neighbor, M31, the Andromeda Galaxy. It is fascinating to realize that when we look out in to space in the night sky that not only are we looking across unimaginable distances, but we are also looking back into time. This is what it means for an object to be 3 million light-years (18 trillion miles) distant - it took the light, traveling at 186,282 miles per second, 3 million years to get here. So we are not seeing M33 as it looks today, but rather as it looked 3 million years ago. Noted observer Tom Polakis says "What is amazing to me is that the galaxy is not all that different today than it was 3 million years ago, since that's not very much time in the lifetime of most stars." North is to the left in the above image.
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