December Gems in Cassiopeia

The Christ­mas sea­son is upon us. Oth­ers may hear the jolly sound of Santa tot­ing up the cash-register receipts. All I can hear is the wail­ing and gnash­ing of teeth as folks learn to use their new telescopes.

You know you really bought the tele­scope for your­self. Besides, how many seven-year-old tele­scope recip­i­ents know how to find Sat­urn? So do your­self a favor. As I have sug­gested in pre­vi­ous columns, pur­chase a good set of star charts for your­self. Also, buy “Jimmy’s” tele­scope before Christ­mas, take it out­side, and learn to find a few objects. After Christ­mas, Jimmy will think you’re an astronerd of the high­est order, and you won’t spend most of Jan­u­ary won­der­ing why you blew all that money on the blessed thing.

After you’ve seen the moon and Jupiter, a good place to go next is the large num­ber of star clus­ters in the con­stel­la­tion Cas­siopeia. Some of them look good in even small tele­scopes, and they’re rel­a­tively easy to find.

First, some back­ground. Star clus­ters are col­lec­tions of stars of about the same age. The stars are all rel­a­tively close together in space because they were born out of the same cloud of hydro­gen gas.

The stars of a clus­ter are only loosely con­nected together by their mutual grav­i­ta­tional attrac­tion. As a result, they are slowly drift­ing apart. Even­tu­ally, they will travel away from each other into the Milky Way galaxy. In the mean­time, these mostly young stars are vis­i­ble in the same low-power tele­scope field.

A mere few mil­lion years will pass before they aren’t clus­ters any more. Check them out before it’s too late.

The show­piece of the area is prob­a­bly the Dou­ble Clus­ter, two star clus­ters that fit nicely in the same medium-power tele­scope field. It looks like two piles of glow­ing gems stacked up next to each other.

Next, look for NGC 663. You’ll see over a dozen bright, yel­low stars sur­rounded by a haze of light. The haze con­sists of the unre­solved glow of many other stars that your ‘scope is too small to see.

My per­sonal favorite is NGC 7789, but I get to use tele­scopes as big as corn silos. In a larger ‘scope, you’ll see at least 100 stars sur­rounded by the same fuzzy glow as NGC 663. In a smaller ‘scope, the clus­ter looks like a ball of light with no indi­vid­ual stars visible.

NGC 7789 is huge, over 40 light years wide, and it’s far away at 5,000 light years. Remem­ber, one light year is equal to about six tril­lion miles. No won­der this ball of 1,000 or so stars doesn’t resolve very well.

M 52 is one of the pret­ti­est clus­ters in the con­stel­la­tion. You’ll see a few bright stars, but even in a small ‘scope, the back­ground haze looks lumpy and rich, as if dozens of stars are just on the verge of pop­ping out of the haze.

NGC 457 is far away at 9,000 light years. You’ll see a hazy, elon­gated glow with a few bright stars.

The bright­est of the stars, called Phi, gen­er­ates a con­sid­er­able amount of con­tro­versy among astronomers. Because it is so much brighter than the other stars, you might assume that it is not really a part of the clus­ter and that it is much closer than the rest of the stars.

How­ever, it appears to be mov­ing through space at the same veloc­ity as the rest of the clus­ter. If it really is at the same dis­tance, it must be pro­duc­ing a whole lot of energy. In fact, it must be 250,000 times brighter than the sun, mak­ing it one of the most ener­getic stars known.

Stars like Phi are called super­giants — dying stars going through a burst of energy before they finally kick the comic bucket.

You’ll find a lot more clus­ters. Explore, enjoy, and put that new tele­scope through its paces.

If all else fails, you can always observe …

Plan­ets

Blaz­ing Venus is low in the south­west dur­ing evening twi­light. You’ll need a clean hori­zon to see it as a small, white dot.

upiter is high in the south­east just after dark. Observe its four bright­est moons in binoc­u­lars and its cloud bands and moons in a small telescope.

Mars is high in the ESE by 4 a.m. as an orange point of light. Tele­scop­i­cally, it’s a tiny orange dot and hardly worth a look.

Sat­urn is always worth a look. To the unaided eye, it looks like a pale yel­low star low in the ESE at about 5:30 a.m. Even a small tele­scope will reveal its jaw-dropping rings.

Tom Burns is direc­tor of Ohio Wes­leyan University’s Perkins Obser­va­tory in Delaware, Ohio. tlburns@owu.edu

Posted by Tom Burns on Dec 4 2011. You can follow any responses to this entry through the RSS Feed. Comments can be made below.