24 Aug 2009
Racial profiling has been a hot topic in our country for years now. Trying to figure out something about someone based on color is a matter for heated debate in the public forum. But in astronomy we judge based on color all the time. We have to. And here it’s pretty reliable.
There is no way to travel to a star and stick a thermometer in it to see how hot it is. We can’t land on these balls of gas and perform experiments. About the best we can do to find out how a star works is to try to replicate in our laboratories what we see out there, then infer things about that far distant star based on our findings.
One of the characteristics of a star is its color. “Color?!” you may exclaim, “I thought all stars were just twinkling white things.” Not at all.
Stars come in all sorts of colors: red, orange, yellow, white, blue. But why? They are colored that way because of their temperatures. You have seen these colors here on Earth when different objects - often metals - glow when they are heated.
You may have seen an iron poker stuck into a fire. At first it gives off no visible light. But if one were to leave the poker in a hot fire for a longer time, you would notice it starts to glow red, then orange, then yellow. If you could heat up the metal in a very, very hot fire it would become “white hot.” Notice that these are all the same colors as stars.
What you may not know is that if you could heat a substance up even hotter than that, it would begin to give off a bluish hue.
Actually, these objects are giving off all the colors of the visible spectrum at once, it is just that they are giving off “mostly” red or orange or yellow, etc., so we see that predominant color as the overall “color” of that object.
Same with stars! The cooler stars are bleeding out mostly red, hotter stars mostly orange. The hottest, most dangerous stars pour out a lot of blue, hence their bluish hue.
The colors of stars are giving us temperature clues, which in turn tell astronomers what is going on inside that hot gas ball trillions of miles away: how they burn, how fast they live, what they are made of. Stellar profiling based on color is an absolutely vital tool in the realm of astronomy.
10 Aug 2009
Going on a vacation to see some of the beauties of nature often involves a lot of work. One must plan, make reservations, pack, get time off, fly or drive to "enjoy" that trip to Yosemite or Yellowstone or the Grand Canyon. Of course it is worth it - they are all terrestrial works of art - but there are some natural wonders which we can enjoy from our own backyard.
Of course I am talking about the sky; but more specifically here, a meteor shower. And - surprise! - we have one in the next days.
The annual Perseid meteor shower is scheduled for its appearance though the middle of this week, more precisely the nights of the 11th and 12th, and the 12th and 13th.
Recall that a meteor shower happens when Earth barrels through a comet's debris train. A what?
Comets, made of ice and organics and dirt, circuit through our solar system often. Some are in hugely elliptical orbits which take decades, sometimes centuries to complete. A few comets have orbits which intersect our own. It is tragic if Earth and comet happen to meet at that intersection at the same time, but we almost never do.
The comet does give off a lot of its dust and ice and other debris as it goes around, especially when it is close to the sun. It is that thrown-off stuff that we are pretty much guaranteed to hit as we cross orbits.
And as we do run into the debris train, those dusty remnants smash into our atmosphere at breakneck speeds, vaporizing the little guys in streaks of light which we call meteors.
We cross the thickest part of the debris train of a comet called 109P/Swift-Tuttle at about midday on the 12th. Bad news: We miss the peak for nighttime viewing. Good news: We can see the shoulders of that peak either the night before or that night.
Sadly, the waning, but still bright, third quarter moon will be up brightening the sky after midnight, just when it is best to see the shower. But that's OK. The Perseids are reliably big and bright and beautiful.
When you go out to watch them, your best bet is from just before midnight to dawn (when we are headed into the stream). You merely need a place to lie down and look up. If it is a warm evening don't forget the bug spray. Mosquitoes see you as a healthy meal lying there all unprotected. Trust me on that one.
Enjoy with your friends or family this inexpensive summer vacation to a natural wonder.