Mar 20, 2009 0
Posted Jan. 30, 2009 – Living in rural upstate New York, I’m very familiar with temperature extremes. Since 1974, I’ve mostly heated with wood. Sounds romantic, but we all know better. I grab icy logs barehanded and lug `em to the house, where any remaining wrist hairs are burned off as I toss ‘em in. En route I peer at the frosty January sky, its stars seemingly detached from the exercise in hot and cold abuse I endure for the sake of economy.
But on second thought, Orion and his friends experience the same thing. 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 marking Orion’s foot, are among the hottest things the eye can see. Rigel emits the same blinding brilliance as 60,000 suns. Such energy output doesn’t come cheaply. Look again in just a half billion years and there’ll be no sign of Rigel, for it’s squandering its resources like a giant Hummer.
More typical stars emit only a sleepy 10% of the sun’s light. Using their nuclear fuel sparingly, they’ll live almost forever. Many have been shining since soon after the Big Bang, and they’ll still be alive ten billion years from now, long after our sun has metamorphosed into a frozen black dwarf.
These red dwarfs are more numerous than all other stellar varieties combined. Of the 100 nearest stars to Earth, 82 are of this type. Yet a glance upward reveals no trace of them. They’re just too cool and dim. Even telescopes only detect the nearest examples.
So the night sky fools us with a false picture of the galaxy’s stellar citizens. We merely see the lighthouses, the energy abusers. Truly typical suns, the thrifty ones, are utterly invisible, a hidden majority.
But the very coolest stars aren’t even those common superfaint 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. R of the constellation Lepus, or R leporis, changes its brightness, and such unstable stars have letter-names. Cool? R is extraordinary. It’s so stingy with its internal fireplace that it appears dramatically coal-red through any small telescope. In fact, finding it is as simple as sweeping a ‘scope below Orion, along an extended line from the rightmost belt star through Rigel, until you come to a crimson star. Such stars are cool enough to be surrounded by water vapor. Steam.
Yet we still haven’t reached the absolute cosmic extremes. The hottest thing anyone now living has ever seen was Supernova 1987A. I traveled to the equator to view it, a dim pinpoint that dominated its entire parent galaxy, emitting more light than a million suns. This was the only naked-eye supernova in three centuries. Supernovas are so hot that, like an alchemist’s lab, lead and iodine are created out of lighter elements, a task even the hottest normal stars can’t accomplish.
The other extreme, the absolute coldest stars of the night, are black dwarfs, not to be confused with black holes. But nobody sees them. They emit no light. You could lie on their surface and feel no heat. Staying warm could be a major problem. Imagine trying to light a campfire on the surface of a star? (A wonderful image, but not easy without an atmosphere.)
But we don’t even have to go as far as the stars to find unpleasant temperature extremes. Venus, now beautifully dominating the evening twilight, bakes at a steady 900 degrees, hotter than an oven. Neptune’s moon Triton, the coldest place in the solar system, shivers at a numbing -400.
And so it goes. No comfort zone. No room temperature anywhere in the known universe. The winter sky gives the appearance of a black frozen expanse punctuated by islands of fiery hell. And that’s just how it is. It makes my own little outings into fire and ice seem a little more bearable. They’re just a reflection of the larger universe, a momentary step away from the odd oasis of our comfortable Earth.