Have you been keeping up with The Boston Globe’s Hubble Advent Calendar? Today’s picture is totally worth talking about, and gives me a chance to tell you about these little guys that just hang-on to our galaxy: globular clusters. When you look out at a galaxy — pretty much any galaxy — you’ll find these tiny clumps of light surrounding it.
These clumps are actually amazing, dense collections of stars! If you look out at the nearest star to us, it’s Proxima Centauri, located just over four light years away. That means if you drew a sphere centered on the Earth four light years in radius, there wouldn’t be a single star in it other than our Sun. If you made that sphere 4.2 light years in radius, you’d finally get the first one.
Globular clusters, on the other hand, must look at us and laugh. Imagine taking that same volume of space that — around our Sun — contains just one other star. Now, instead of filling it with just one star, fill it with around 100,000! Our galaxy has around 200 globular clusters in it, with some of the largest ones containing many millions of stars, despite having a physical size of only around 100 light years! (And for this and all subsequent images, click for the largest available version. Some of the images are large!)
Well, this seems like the type of thing Hubble was built for! In 2002, we pointed Hubble at one of the largest globular clusters we know of, Omega Centauri, and instead of looking like this, which it does through a ground-based amateur telescope,
Hubble returned this picture, which you can see on the advent calendar.
There are about 2 million stars in this image, which is less than 20% of all the stars in the globular cluster. Now, I could crop a small piece of this image to show you how impressive Hubble’s telescope was in 2002; here you go!
But didn’t they just upgrade their camera? What do you suppose we’d be able to see with the new camera if we took another look at Omega Centauri today? Maybe… something like this?
And if you zoomed in to the full-resolution version and pulled out what’s really inside, at the highest resolution possible?
Well, if you’re not impressed by what’s in there, you need to check your pulse, because you’re probably dead. For perspective, this cluster is 17,000 light years away, and the distance spanning this last entire image is less than two light years.
And that’s worth celebrating at any time of the year.