STAR GAZER
THE INTERNATIONAL EDITION
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Horkheimer: Greetings, greetings fellow star gazers. Everyone loves winter's brilliant constellation Orion the Hunter because his three belt stars are the only three stars equally spaced in a row we can see with the naked eye. But the two bright stars above the belt and the two bright stars below the belt are also quite wonderful.
O.K. We've got our skies set up for just after it gets dark out facing southwest. To find Orion simply look for the three bright evenly spaced stars in a row, which mark his belt. The two above of course are his shoulder stars and the two below mark his knees. Now although the night sky doesn't look very three dimensional, in reality all the stars are different distances away from our Earth and each other. And one way to measure these distances is with the speed of light. Light travels 186,000 miles a second. So when we look at the star closest to Earth, which is our Sun, since it is 93 million miles away we see the light that left it 8 and 1/3 minutes ago. So we say that our Sun is 8 1/3 light minutes away. All the other stars however are so far away it takes years for their light to reach us.
For instance of Orion's four bright stars his shoulder star Bellatrix is the closest, 240 light years away which means we see the light that left it 240 years ago. Betelgeuse the next closest is over twice as far away, 520 light years. Which means we see the light that left it 520 years ago. But Orion's two knee stars are even farther away. Rigel is 800 light years and Saiph 820, which means that the light we see now, left them 300 years before Columbus' voyage to America. Wow! To remember the distances closest to farthest, just remember right shoulder, left shoulder, right knee, left knee. What's equally impressive is that stars come in all different sizes. And the easiest way to illustrate this is to compare them to our almost million mile wide Sun, which is considered a rather small star. Orion's shoulder star Bellatrix is 6 times as wide as our Sun which really sounds impressive until you look at the knee star Saiph which is 38 times as wide as our sun.
And it gets even better. The other knee star Rigel is 50 times as wide as our sSun. But you ain't seen nothin' yet, because Betelgeuse, the red shoulder star, is a what we call a variable star and changes its size regularly. Contracted to its smallest size it is 500 times as wide as our sSun and when it is expanded to its largest, 900 times as wide. Wow again! And an easy way to remember the order of size of these stars is right shoulder to left knee to right knee to left shoulder. So get thee out and try to imagine the sizes and distances of each of these four stars. And believe me after a while you'll almost see them in your mind in three dimensions. Keep looking up!
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Horkheimer: Would you like to see the stars in 3-d? Just after dark face southwest, find Orion's belt stars, shoulder stars and knee stars. Now although Orion doesn't look three dimensional, in reality these stars are different distances away from us. From closest to farthest the shoulder star Bellatrix is 240 light years away, which means we see the light that left it 240 years ago. Betelgeuse is over twice as far, 520 light years. But Orion's knee stars are even farther. Rigel is 800 light years and Saiph 820, which means the light we see from them now left them 300 years before Columbus' voyage to America. Wow! Keep looking up!
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* This week's Sky At A Glance and
Planet Roundup from Sky & Telescope.
This week's Sky At A Glance displays current week only.
Starry Night Deluxe was used to produce this episode
of Star Gazer
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