It’s Full of Stars!
Saturday, May 19, 2012
Several astronomical objects can lure me out into a dark sky to gaze upon majestry of the heavens. One is the Milky Way, the second is the August Perseid meteor shower, and the third is best summed up by the exclamation, above.
The sci-fi gurus among you will quickly recognize the title as exclaimed by David Bowman as he enters the “stargate” in 2001: A Space Odyssey. It was an early version of the Star Wars “jump speed” effect, with a mix of Time Tunnel, Sliders and Stargate-SG1. Though the object I love to examine does not display any of the motion the above mentioned special effects do, it is definitely full of stars, hundreds of thousands of stars!
I’m referring to the showpiece of northern hemisphere globular clusters, M13 in Hercules (so called for being the 13th entry in the sky catalog of 18th century astronomer Charles Messier). But before I describe this beautiful cluster of stars, let’s examine the Hercules star pattern with its wealth of associated mythology.
A constellation "giant"
The origins of this constellation “giant” remain shrouded in the dim recesses of mankind’s past. The fact that this particular pattern of stars has always represented a giant lends credence to the idea that its form has remained unchanged for perhaps thousands of years. In this scenario, different cultures merely borrowed the form and tailored it to their own circumstances. The “kneeling one,” as the ancient Greek astronomers knew him, has come to us now in the form of Hercules.
GET THE LATEST BREAKING NEWS HERE -- SIGN UP FOR GOLOCAL FREE DAILY EBLASTThe myth behind the man
Let’s examine the myth behind the man. Hercules was the son of the god Jupiter and a mortal woman, Alcmene. This union gave Hercules superior strength and other powers mortals did not possess. He was first put to the test as a child when he strangled some snakes the goddess Juno had sent to destroy him. You see, Juno was Jupiter’s wife, and she was fed up with her husband philandering with mortal women.
As a young man, Hercules’ strength and courage were both fully tested by King Eurystheus to whom Hercules owed allegiance. The king was jealous of Hercules' fame as a hero, so he imposed twelve labors upon him. The king really wanted Hercules out of the way, since any one of the twelve tasks could have easily killed him. To make a long story short, Hercules succeeded in all the tasks, elevating him to even higher hero status.
However, Hercules’ ascension to the starry heavens is a tragic one. One day, as Hercules was about to set out on a journey, his wife Deianira presented him with a cloak. Unfortunately, she had received it as a gift from the dying centaur Nessus, whom Hercules had slain. The cloak was poisoned with the centaur’s blood. Hercules knew his undignified death was at hand, so he built a funeral pyre on Mount Etna, placed himself upon it, and set it afire.
In today’s sky we find the mighty Hercules, kneeling upon the head of Draco the Dragon, holding a club in one hand, and a branch in the other.
How to find the constellation giant in the sky
Now that we know a little about the mythology of Hercules, where can one find this constellation giant? Once the evening twilight fades during mid to late May to early June you will find Hercules about halfway above the east northeast horizon between 9 and 10 pm. Keep in mind that Hercules rises on his side with his head facing south (right), so the constellation picture of this star pattern may be a little difficult to recognize.
Four main stars, called the keystone, outline the body of Hercules, while two streams of stars form his arms and another stream comprises his legs. Though his extremities look like a stick figure, Herc has been bulking up on his body. A simple constellation star wheel will surely help you to locate and identify Hercules.
To locate the beautiful globular cluster M13, it can be found between the two stars that form the western side of the keystone. It is about 1/3 of the way from the northern most star of the keystone. While M13 can be seen with the naked-eye in a dark sky, try using a pair of binoculars. It will look like a tiny tail-less comet.
Once you’ve found it, use a telescope if you have one. You’ll see a magnificent cluster of stars. A small refractor will show M13 as a small diffuse patch of light, much like the nucleus of a comet. Larger scopes, say a four- or six-inch reflector, will begin to resolve individual stars within this beautiful beehive of stars. And the beehive description is quite apt, for if one could speed up time you would see these stars, which are all gravitationally bound to the cluster and number about 300,000, “orbit” the cluster like bees around a hive.
One of my favorite turn-of-the-20th-century authors is Garrett P. Serviss. I often quote him in my columns because he had such a descriptive and poetic style of writing. For your enjoyment I have excerpted two quotes concerning M13 from his wonderful book, Pleasures of the Telescope:
“...smaller instruments reveal only the in-running streams and the sprinkling of stellar points over the main aggregation, which cause it to sparkle like a cloud of diamond dust transfused with sunbeams…It is a ball of suns. Now you need a telescope. You must have one. You must either buy or borrow it, or you must pay a visit to an observatory, for this is a thing that no intelligent human being in these days can afford not to see. Can it be possible that any man can know that fifteen thousand suns are to be seen, burning in a compact globular cluster, and not long to regard them with his own eyes?”
On the next clear and moonless night, go out and locate the great Hercules in the sky. Binoculars will certainly show you M13, but a telescope will reveal all its splendor. Think about the above descriptions while you enjoy the image. Also remember Bowman’s exclamation, “It’s full of stars.” You may not enter a stargate, but starlight can certainly provide you with a trip through the universe.
And don’t forget that the local observatories are always “full of stars,” providing the skies are cloud-free. On the next clear Saturday night take a ride out to Seagrave Observatory (http:/www.theskyscrapers.org) in North Scituate. After the June 5 transit of Venus, Ladd Observatory (http://www.brown.edu/Departments/Physics/Ladd/) in Providence will be closed for the remainder of June and all of July for annual maintenance. However, the exceptionally dark skies of Frosty Drew Observatory (http://www.frostydrew.org/) in Charlestown, open every clear Friday night, will show M13 in all its glory. Check out each website for the public night schedules and opening times.
Keep in mind we can’t begin to observe the stars until around 9:30pm the closer we get to the summer solstice, which occurs at 7:09pm on the 20th of June.
Until next time, keep your eyes to the skies.
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