Tom Burns: Bunnies and a blood-red star


Tom Burns - Stargazing



The powerful hunter Orion stands high in the southern sky right now. He has conquered many a brave foe. And what valiant enemy have the gods chosen to immortalize by placing it in the sky? A bunny rabbit, that’s what.

OK, it’s not, strictly speaking, a bunny. We’re talking Lepus, the Hare, a somewhat larger version of the rabbit.

Lepus is not a well-known constellation, outshone as it is by Orion to the north. Look for it underneath Orion’s rectangular-shaped outline. This old galley rhyme, which I found in RH Allen’s wonderful old book “Star Names: Their Lore and Meaning,” will tell you where to look:

Orion’s image in the south

Has four stars — small but fair;

Their figure quadrilateral

Points out the timid Hare.

Orion is thus standing on Lepus. He seems to celebrate his victory over this fluffy denizen of the night. Seriously, bunnies can be dangerous in their own way, as the story associated with Lepus suggests.

The island of Leros, off the southwest coast of Turkey, had no hares, or so the story goes. They were considered very tasty, so somebody got the bright idea of bringing in a pregnant female. Well, we all know what these long-eared rascals like to do.

So pretty soon, the island, which is only 20 or so square miles in size, was crawling with Thumper’s cousins. They ate everything, including the entire agriculture output of the island. The populace was reduced to starvation.

The Lerosians had to work hard at it. If you’ve every tried to chase down a rabbit, you’ll know what I mean. In at least one version of the story, the inhabitants sought the help of the mighty hunter Orion. Of course, Orion was not averse to bunny slaughter. He once boasted that he had killed every kind of animal on Earth. What are a million or so delectable rodents, more or less?

In any case, the Lerosians finally killed all the hares or drove them into the sea. I’m sure rabbit stew was on the menu for a very long time.

The gods put Lepus in the sky to remind them (and us) to avoid wretched excess. Orion is standing on the hare to make sure it stays put.

At Perkins, we spend quite a bit of time in the winter talking about Orion and his environs. His faithful huntin’ dawg, Canis Major, follows at his feet. His club is raised in unending battle with the pugnacious bull, Taurus.

We spend little time talking about Lepus. It isn’t exactly full of objects for the stargazer to look at.

One object is a globular cluster marked as M79 on most star maps. This dense ball of more than 100,000 stars is as bright as perhaps 90,000 of our suns, but it’s so far away that it isn’t much to look at.

M79 is visible in binoculars as a faint, fuzzy patch. A moderate-sized telescope will begin to resolve some of the stars around its edges. At 50,000 light years away from Earth, M79 is about as far away as you can get and still be in our Milky Way galaxy. (A light year is equal to 6 trillion miles.)

Lepus wouldn’t be worth bothering about except for one really strange and spectacular star called R Leporis. Long ago, when I was the one on the front lawn at Perkins pointing a telescope, I always found time to point my big ’scope at this strange star.

Over about 428 days, “R” changes from very dim, so that it can be seen only in a large telescope, to bright enough so that it can be glimpsed by the naked eye under very dark, rural skies, and back to bright again.

Such variable stars have extreme changes in their brightness because they’re very old.

As stars get older, they have less and less hydrogen to burn into helium. As their thermonuclear fires falter, they cool off. The explosive pressures at their center cause them to expand to enormous size, radiate a lot of energy into space, and get temporarily brighter.

As heat and light is radiated, the central explosive pressures lessen. Gravity takes over, allowing them to contract a bit and become dimmer. This cycle can repeat itself millions of times before the star finally burns out.

At less than 6,000 degrees Fahrenheit, R’s temperature is much lower than that of a yellow star like our sun, which is medium hot at 10,000 degrees.

Its low temperature allows R to keep a lot of carbon in its shell. As its light shines through its atmosphere, the blue light is filtered out by the carbon, which is what gives it its distinctly red color.

And that’s what makes R so special. In a sky filled with white stars, bluish stars, and even pale orange stars, R shines a deep crimson.

Its discoverer, J.R. Hind, described it in 1845 as “resembling a drop of blood on the background of the sky.” Color, especially red, is hard to discern at night. Hind’s Crimson Star, as R Leporis is sometimes called, simply blows you back from the telescope.

Observing a star like R can be a frustrating experience because its brightness affects its color. One year, it is easy to find in binoculars, but it looks more coppery than red. The next year, only a telescope will show it, but then it looks like a glowing drop of deep red wine on the face of the night.

However, its bright red color never fails to amaze. It is like a crimson heart beating slowly to the rhythm of the cosmos.

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Tom Burns

Stargazing

Tom Burns is director of the Perkins Observatory in Delaware.

Tom Burns is director of the Perkins Observatory in Delaware.