Sirius, Seriously!

Observing >

There is a star in the winter skies --- a seriously bright star --- called Sirius.

You can't miss it; it's one of the brightest objects up there. Just follow Orion's Belt down to the brilliant, flashing glimmer of Sirius, the "Dog Star."

Sirius is part of the constellation Canis Major, Orion's big dog. It is not only the eye of the dog, it also makes up part of what might be known as the Winter Triangle. The other two stars of the triangle are Betelgeuse, the bright orangey star in Orion, and Procyon, which rises just a half hour before Sirius. Procyon means "before the dog," a name betraying both its position in the sky and its position of importance, secondary to Sirius.

Although high in the sky now, Sirius rises just before the sun in later summer, when the days are hot and miserable. Hence, the "dog days of summer."

It is this link with the heat of summer that leads most to believe that the name Sirius originated from the Greek "seirios" which translates to The Scorcher; as in, "The Scorcher is seen as a seriously searing star."

But one is hard-pressed to find agreement about the source of Sirius' name because a number of other cultures have similar sounding names for it. The Greeks called it Osiris, the Celts Syr, and the Egyptians Cahen Sihor.

It was the Egyptians who revered the Dog Star to the point of worshipping it. The annual rising of Sirius with the sun was simultaneous with the flooding of the Nile, an ultra-important yearly phenomenon for Egyptians.

The flooding would fill the plains with sediments making the land fertile again.

For us in North America Sirius is not only the brightest star, it's the nearest we can see. (Proxima and alpha Centauri are closer, but we can't see them here in the north.) Sirius is just a star's throw away at 8.6 light years, in the next room by astronomical standards. Its surface roils at 15000 degrees Fahrenheit, not too much more than our sun's 10000 degrees. And it's only twice the mass of the Sun.

But the laws of nature are such that all those numbers mean it spews out about 30 times more energy! Sirius' closeness and luminosity make for a bright, beautiful star.

And it turns out Sirius has a little buddy!

In the 1830's Sirius was detected to wobble in the sky a wee bit. Wobbling implies something is very near you causing you to wobble about. So what was doing the salsa with Sirius?

It wasn't until the 1860's, when telescopes got big enough, that a companion was finally spotted. But that was just the beginning of a mystery.

Through a little math work it was found that Sirius' buddy was a little buddy, a really little buddy, just a tiny fraction of the Sun's size. But it was bleeding heat, with a surface temperature more than 5 times as much as the Sun!

The Pup, as it was called, was amazingly dense, as well. Just a teaspoon of Pup Stuff would weigh 5 tons on Earth!

What was this new doggy in our window?

It turned out the Pup was the first white dwarf star ever discovered. Stars like our own don't go out with a bang like giant stars do when they supernova. Sun-like stars shed their outer layers as they die, finally exposing a white-hot superdense core below --- the white dwarf. These earth-size stellar corpses can be found all over, often orbiting other stars as here with our brilliant neighbor Sirius.

Until next time, clear skies!

Mark Ritter teaches astronomy at Temecula Valley High School and can be reached at mritter@firstlightastro.com.

Posted by Administrator at 2003.01.18 01:54 PM | Comments (0)

Stellar Resolutions

Observing >

You've already made New Year's resolutions. And you've already broken them, haven't you? They were too unrealistic and besides, you don't really want to give up donuts anyway. Here's an astronomical spin on the traditional resolution-making, and a chance to start again with resolutions more easily fulfilled and more likely to make you a more fulfilled person. Try and commit to at least a couple --- they're so easy! Ready?

1. Look through a telescope this year. Not a cheesy, 50 dollar, "magnifies 10 million times" piece of rubbish --- a real telescope. Ask a friend, or your local neighborhood purveyor of telescopes, or a member of an astronomy club. Choose a moonless, clear night, then take your sweet time and scan the skies. You'll see more stars than you can count, along with nebulae and star clusters and planets. Afterwards, you might even consider buying a scope (but not without consulting an expert first as to what's best for you!)
2. Look at Saturn and Jupiter through a telescope. This is related to #1 above, of course, but specifically look at these two, high in the sky for the next few months. See Jupiter with its tiny moons and violent atmosphere streaked by breakneck winds. Experience Saturn and its other-worldly ring system. It is an encounter you will never forget.
3. Experience a meteor shower. There are several good ones during the year, like the Perseids in August and the Leonids in November. And don't think observing a shower means looking out the kitchen window for a couple minutes after dinner. Go out after midnight, dressed warmly, binoculars at the ready --- for a couple hours! Count how many you see. Tell your friends the next day how crazy and spontaneous you are.
4. Turn off your outdoor lights at night before bed, or put them on a timer. The night skies are being polluted with light, all of it wasted. Some of us old fogies can remember when the skies were dark and full of stars. Commit to turning off the lights this year; the next generation needs to see the skies!
5. Make some periodic observations, observations that show you something after a length of time. For example, on your way to work or school watch how Venus changes position through the morning sky, eventually disappearing into the sunrise, only to pop up a couple weeks later at sunset. Or see how the sunrise and sunset occur at slightly different positions every day. Or notice the Moon changing phase every day and learn to predict what and where it will be tomorrow. You'll become kindred spirit to the countless generations of humans who have done this before you, setting their calendar by the sky.
6. Just go out and look. Once a season, when the stress of the job is getting to you, or you've had it with driving the kids to soccer, or you finally realize there's more to life than TV and bills, go outside. Pick a day far from Full Moon, sit back on one of those things people like to sunbathe on, and starbathe instead.

Take in the full beauty and majesty of the cosmos. Just absorb the wonder of it all. Experience, or re-experience, the idea that in the vast celestial sphere above you, stretching out billions of light years in all directions, there is this one tiny planet, teeming with life, with a perfectly designed human being laying in his backyard aware and in awe of the magnificent universe he lives in.

Then go in and give your kids a hug.

Mark Ritter teaches astronomy at Temecula Valley High School and can be reached at mritter@firstlightastro.com.

Posted by Administrator at 2003.01. 4 01:56 PM | Comments (0)