Looking Up: Small Galaxy - It's What's For Dinner

May 13, 2019

This huge ball of stars predates our Sun. Long before humankind evolved, before dinosaurs roamed, and even before our Earth existed, ancient globs of stars condensed and orbited a young Milky Way Galaxy. Of the 200 or so globular clusters that survive today, Omega Centauri is the largest, containing over ten million stars.
Credit Roberto Colombari / nasa.gov

Perhaps all that 'core training' Omega Centauri did in the past really paid off. It may very well be all that's left of a small galaxy that collided with the Milky Way a long, long time ago. That's the story Hal has for us on this week's Looking Up.

Today I’m going to tell you about a wonderful object in the southern Colorado sky, the amazing Omega Centauri! It isn’t easy to find, and you will have to have a very flat southern horizon to spot this elusive object.

At our club’s observing site, Starry Meadows near Gardner, Colorado, we have to time it just right to catch a glimpse of this object when it is between mountain peaks on the horizon, during our annual star party, Rocky Mountain Star Stare – see rmss.org for more information.

Omega Centauri may look like a big globular cluster, such as the Hercules Cluster and other famous balls of stars, but it may well be something very different. It is undeniably beautiful, but astronomers now believe it hides an amazing story. Once thought to be an “ordinary” globular cluster, one of over 150 in the sky, we now think it might very well be the leftover galactic core of a galaxy that collided with the Milky Way galaxy many eons ago.  That’s right, our Milky Way likely ate an entire small galaxy that got too close, It’s visible to the naked eye if you can get to the right place to see it, and it’s a gorgeous reminder of a lost galaxy, our galaxy ate. Bon appetit! 

NASA's Hubble Space Telescope snapped this panoramic view of a colorful assortment of 100,000 stars residing in the massive globular cluster Omega Centauri, which boasts nearly 10 million stars.
Credit NASA, ESA, and the Hubble SM4 ERO Team / nasa.gov

If you’d like to take a closer look at Omega Centauri, or any of the other wonderful and amazing things in the sky, please visit csastro.org for a link to information on our monthly meetings and our free public star parties!