Thursday, February 28, 2008

Leaping Lepus

As it is Leap Year--and Friday the 29th, Leap Day--let’s visit a constellation with some spring in its step: Lepus the Hare. This unassuming little constellation is one of my favorites, because it features a couple fine telescope objects.

Lepus (pronounced LEEP us) is in perennial flight from the hound dogs of the hunt, Canis Major and Canis Minor. He is well equipped for the chase. Hares, long-eared cousins of the rabbit, have been known to attain speeds of around 45 miles per hour.

Lepus in 17th century star atlas
Courtesy of
Linda Hall Library of Science, Engineering and Technology

If you’re out under the night sky for a few hours, you’ll notice that Lepus and his canine pursuers travel from east to west over time. The stars are not actually moving west. We see this apparent motion because Earth is turning on its axis 24/7, toward the east. In the case of the hare and hounds, the effect is quite theatrical. The hare manages to stay a hop and a skip ahead of the dogs, but after midnight is relentlessly hounded right over the western horizon.

Unfortunately, the stars in Lepus are not terribly bright. Stargazers in the far northern latitudes may have some difficulty spotting the hare as he scampers under Orion’s feet, low near the southern horizon.

Let’s leap!

1) You’ll need to face south, so 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 right shoulder to the west, and you’ll be facing approximately south.

2) Wait at least one hour after sunset to begin observing, so your sky is nice and dark. During this observing week, the moon is waning (shrinking) and will not rise to wash out the sky with its bright light until after midnight. You’ll have plenty of ‘prime time’ observing hours.

3) Locate Orion the Hunter by spotting his hourglass-shaped asterism (recognizable star pattern). One hour after sunset, Orion is nearly due south. He hangs halfway to two-thirds of the way up from the southern horizon toward the zenith (the point directly above your head).

4) Below the blue supergiant star Rigel, at the lower right corner of the Orion hourglass, look for a small triangle of faint stars. These represent the Hare’s Ears. Below and to the left of the ears are the two brightest stars in Lepus, which are in the hare’s body.

Lepus star map

5) The top star of the two is Arneb, the brightest star in Lepus. Arneb (pronounced AHR neb) is a red supergiant whose name is Arabic for hare.

6) The bottom star of the two is Nihal (pronounced nih HALL), from the Arabic for camels beginning to quench their thirst. Nihal--along with Arneb and the two fairly bright stars to the left of them--form an ancient Arabic star grouping that represented four camels drinking from the ‘river’ of the Milky Way. Nihal is a yellow star, a giant version of our Sun.

7) If you have a telescope, or access to a telescope, take a look at one of my favorite globular clusters, Messier 79 (pronounced MESS ee yay). M79, as it is commonly known, is a dense ball of gravitationally bound stars. There are 150 globular clusters in the Milky Way, our home galaxy. I like M79’s whimsical star streamers. I hope you do too.

You’ll need a clear view of the southern horizon to claim this globular, since it sits low in the sky below the figure of the hare. A small scope like the Starblast Astro will snare the object, and it will look like a small fuzzy blob. Using a larger scope like a six-inch reflector, you’ll begin to resolve the fuzz into pinpoint stars. Point your telescope at the spot marked M79 on the Lepus star map above.

8) Another must-see deep-sky object in Lepus is Hind’s Crimson Star, named after the astronomer who discovered it. This is one of the most spectacular red stars in the sky. Hind’s Crimson Star is a carbon star, and as the term suggests, it has an unusually high carbon content. This carbon abundance results in the signature deep-red color. Carbon stars are among the coolest in temperature and are considered rare.

You’ll need a telescope for this object also. Try making an imaginary equilateral triangle with the bottom star and the top right star of the Hare’s Ears, with the third point out to the right of those two. Then use your telescope to search for Hind’s Crimson Star (aka R Leporis) near that third point. Make small, ever-widening circles with your telescope until you find it. Yes, it will be a bit of a challenge to target, but there will be no mistaking its brilliant color.

Courtesy of Ad-Libs Advertising, Inc. (dba Astronomics and/or Christophers, Ltd.)

Call me mad as a March hare, but I think you’ll find this object worth the extra effort.