Jewels in the Spring Sky

4/20/08 – 4/26/08
by C. Zaitz

If you like sparkly things, there is something in the spring sky worth looking at. We’ve been used to dashing from car to work, and back home, without so much as a quick glance skyward all winter long. But now we’re beginning to walk and jog after work, to play with the kids and the dog in the yard, and to notice the outdoors a little more. So what are we seeing in our spring sky? On spring evenings, the stars can glitter wildly as the moving air blinks and twinkles their light. Moving air causes the light from distant stars to jump around and blink on and off like Christmas lights. As pretty as it looks, it makes the image in a telescope look blurry. But when the wind dies down and the temperature rises, there are some spectacular sights to be seen. Two that I'd like to describe look like fuzzy blobs in the sky, but turn spectacular jewels through a telescope.

The first is a very famous fuzzy blotch that is very hard to see with the naked eye, but is one of the most popular destinations for telescopes and binoculars. It is called M-13, but we know it better as the Hercules Cluster. It is a giant group of stars called a globular cluster. Globular clusters are common in galaxies, but they are rebels in a sense. They don't generally ride the spiral arms of the galaxy like the rest of the stars. They can be found high above or below the plane of the Milky Way, in its halo. Spring is an excellent time to spot globular clusters, because we are looking out away from the plane of the galaxy, to the halo area where they live. The Hercules cluster is home to over a million stars, but the true beauty of the cluster comes from the fact that the stars are much closer together than stars in the rest of the galaxy. Instead of a 3 light year average separation, the stars of M13 are on average only one light year apart, making the cluster dense and very brightly sparkly. It's a trick I would use if I was a jeweler and had diamonds to set. The dense packing of stars in a globular cluster make them some of the most beautiful objects to see.

Another famous cluster seen in the spring is M44, known as the Beehive cluster. It is just in front of the sickle shape of stars that marks the head of Leo the Lion. It is one of the nearest and largest open clusters we can see, and therefore one of the brightest. You can see its fuzzy glow with the naked eye, but both clusters really shine when you view them through a telescope. Their true nature will be revealed as you begin to see the individuals making up these vast clouds of stars. Open clusters are made of young, hot, blue stars, and live in the plane of our galaxy, so they are different in appearance and make-up from globular clusters. If I were trying to match their character as a jeweler, I would select the brightest and clearest diamonds to set in a less dense, but still brilliant way.

To find these beautiful objects, it's always good to know your way around the sky. If you spend a little time in the spring with a flashlight and star map, you can see them for yourself. And who couldn't use some sparkly in their life?

Until next week, my friends, enjoy the view.