Thursday, September 10, 2009

Cassie's Cluster

Note: There will be no September 17 post so that I may prepare for the STAR-HOPPERS weekend workshop in astronomy for grandparents & grandkids. Enjoy the September 10 post or browse my older posts. I'll be back with a new post on September 24.

Messier 52 in the constellation Cassiopeia the Queen is one of my favorite open clusters. I like its rich star field and its somewhat fan-shaped appearance. I also consider it a big plus that it’s easy to find.

An open cluster is a loose collection of stars that formed around the same time in the same nebula (cloud of gas and dust). You might think of an open cluster as a sort of family group.

Messier 52, or M52 as it is commonly known, is one of the 110 celestial objects in the catalog of famed 18th century French astronomer and comet-hunter Charles Messier (pronounced MESS ee yay). This catalog is used extensively by amateur astronomers as an observing list, since it contains some of the “best and brightest” deep-sky objects in the night sky. Messier discovered M52 in 1774, while “chasing” a nearby comet.

M52 is easy to find because you can use the distinctive Lazy W asterism (star pattern) of Cassiopeia to locate it. Grab your binoculars, and let’s take a look at Cassie’s cluster.

1) About an hour after your local sunset time, face north. If you don’t know the cardinal directions at your location and you don’t have a compass, make note of where the sun sets on the horizon. That spot is approximately west. Stand with your left shoulder to the west, and you’ll be facing approximately north.




Looking north to Cassiopeia's Lazy W
Star maps created with
Your Sky



2) Look for a W-shaped group of stars east of the meridian. This is the central asterism of Cassiopeia, the Lazy W. Cassiopeia is a circumpolar constellation, one that circles the North Celestial Pole, the imaginary fixed point in the sky directly above the North Pole. Luckily for us, there is a star extremely close to that point in the sky, which serves as a navigational marker. This is Polaris, the North Star.

Cassiopeia and the other circumpolar constellations appear to make a complete counterclockwise circuit around the North Star, over the course of one day. But they’re not really spinning around the North Star. This apparent motion, or the way they appear to move in our sky, is caused by the rotation of the Earth, as it spins on its axis like a top, 24/7.






3) From Shedar (SHEDD-er), the lower right star of the W, draw an imaginary line through Caph (KAFF), the upper right star of the W. Then extend that line the same distance again past Caph, plus a skosh. Train your binoculars on that spot, and you should see a fuzzy patch. With a small telescope, you’ll be able to resolve the stars in the cluster, that is, they’ll separate into distinct points of light.

M52 lies around 5,000 light years from Earth. One light year is the distance light travels in one Earth year, nearly six trillion miles. The cluster is estimated to contain 200 members.




The open cluster M52
Credit: AURA/NOAO/NSF




Two hundred family members in one place at the same time makes for quite a reunion. Pass the potato salad, please.







Astronomy Essential: The universe began with the Big Bang.

The Big Bang is a widely accepted scientific theory of the origin of the universe. It postulates that about 13.7 billion years ago, the visible universe was extremely dense and extremely small— about the size of a dime. This singularity suddenly expanded to create the large-scale universe, which continues to expand today.

Many astronomers accept that a Big Bang event is the best current explanation for some key observable features of the universe, such as: its continuing expansion from a smaller, denser state; the microwave radiation “glow” that is present throughout the universe; a consistent abundance of simple elements such as hydrogen and helium throughout the universe, even in the oldest objects; and a limit on the age of stars in the cosmos.

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