The Sciences

The Ultimate Icebox

Stars come in a wide range of temperatures.

By Bob BermanFeb 1, 1993 6:00 AM


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Living in a rural region of upstate New York, I’ve known temperature extremes. Until last year, when I left the raccoon economic bracket in defiance of the national trend, my house was heated solely with wood. Romantic? This was the reality: icy logs grabbed bare-handed and lugged up the hill to the house, then loaded into the crackling stove, which ignited my few remaining wrist hairs. En route I’d peer at the frosty February sky, its stars seemingly detached from the exercise in hot-and- cold abuse I was enduring for the sake of economy.

But in reality Orion and his stellar companions were shining examples of the same prosaic process. For what are we seeing in the winter sky if not an immense display of temperature extremes and fuel economics?

Giant blue stars like Rigel, which marks Orion’s heel, are among the hottest things the eye can see. Rigel--the seventh brightest star in the sky--emits the same blinding brilliance as 25,000 suns. Such energy output doesn’t come cheaply. Look again in just a few million years and there’ll be no sign of Rigel, for it’s squandering its resources like the Department of Redundancy Department.

More typical stars emit only a sleepy 10 percent of the sun’s light. Using their nuclear fuel sparingly, they’ll live almost forever. Many have been shining since the very first stars of the universe turned on, and they’ll still be alive 10 billion years from now, long after our sun has metamorphosed into a frozen black dwarf.

Such wallflower stars are more numerous than all other stellar varieties combined. Of the 64 nearest stars to Earth, only 4 are brighter than the sun. Most are very much fainter and cooler, and a glance upward reveals no trace of them. They’re just too cool and dim. Even telescopes can detect only the nearest examples.

But the coolest stars aren’t even those routine faint ones. For a really cool customer, you want a carbon star. A fine example lurks just below Orion, in the pretty constellation of Lepus the Hare. Its name is R. I’m not protecting its identity--it’s really known simply as R of the constellation Lepus, or R leporis.

Cool R is extraordinary. It’s so stingy with its internal fireplace that it appears dull red through any small telescope. If it weren’t so large, we wouldn’t be able to see it at all. Finding it is as simple as sweeping a scope below Orion, along a line from the rightmost belt star through Rigel, until you come to a crimson star. R and other carbon stars are cool enough to have water vapor in their atmospheres. While steam might suggest saunalike warmth, it really signifies a fascinatingly feeble atomic furnace.

Yet we still haven’t reached the cosmic temperature extremes, the very coldest stars of the night: black dwarfs. Nobody can see them, though—they emit no light or heat. But we don’t have to go to the stars to find extremes of hot and cold. Venus, now beautifully dominating the evening twilight, bakes at 900 degrees. Neptune’s moon Triton, possibly the coldest natural spot in the solar system, quivers at a forbidding -400.

So it goes. No comfort zone. No room temperature anywhere. The winter sky gives the appearance of a frozen black expanse punctuated by islands of fiery hell. And that’s just how it is.

It makes our own little outings into fire and ice seem a little more bearable. They are, after all, just a reflection of the larger universe, a momentary step away from the odd, comfortable oasis of Earth.

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