What’s up in the sky – for March 2009
Welcome to the podcast.
I’m Scott Hildreth, astronomy professor at
The best way to use this podcast would be to download it to your favorite MP3 player, and go outside any clear night this month, about 9 O’clock in the evening, as far away from street lights or other illumination as you can get. You don’t need a telescope – we’ll just explore with our eyes together, and see what we can see! So if you aren’t already outside, pause this podcast now, grab a friend, and join me … for the stars!
So let’s get started! As always, we’ll begin by looking west, in the general direction that the sun set.
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Tonight low in the western sky about the width of your hand held out in front of you, above the horizon, you’ll see two medium-bright stars. These are Sheratan, on the bottom, and Hamal on the top – the two brightest stars of the constellations Aries, the Ram. Hamal is about 70 light years from the Sun, and we can see it because it is REALLY bright – about 90 times brighter than our Star.
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Look a little higher, and you’re looking at the constellation of Taurus the Bull. See if you can spot a small little cluster of stars – those are the Pleiades, also known as the seven sisters, or the Suburu.
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Now let’s look South.
Turn to your left, and look for three very closely – spaced, equally bright stars, about half-way up in the sky from the horizon – or about two outstretched hands up. These stars make up the belt of the constellation of Orion, the Hunter I’ll pause for a few moments and let you find them!
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Orion is one of the only constellations that everyone on Earth, in both the northern and southern hemispheres, can spot. Those three bright stars you saw – named Alnitak, Alnilam, and Mintaka from left to right – were known as the string of pearls by Arabic skywatchers of 1200 years ago. Above them and a bit to the left, you should see a bright red star – that is Betelgeuse, an enormous supergiant. And below and to the right of the belt a bit, you’ll see Rigel, a bright white star.
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If you follow Orion’s belt like an arrow, from right to left, you’ll see it pointing towards another very bright star – the brightest in fact you can see. That is the star SIRIUS, and it is in the constellation of Canis Major – the big dog – think of it like Orion the Hunter’s Labrador retriever! J Sirius appears bright because it is nearby - relatively speaking. At just a bit over 8 light years away, Sirius is really our next door neighbor to the sun.
But you’re still looking at its light that left in the year 2001.
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Now let’s look East.
Turn again to your left, and look for a fairly bright object, underneath what should look like to you as a small triangle. I’ll pause for a few moments and let you find it! It’s the planet Saturn!
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Did you find it? Well, don’t expect to see its rings – this month Saturn is about 800 MILLION miles from Earth, and were pulling away from it just like a faster car on an inside lane on a racetrack. It was 400 years ago this year that Galileo also looked at Saturn with his \telescope, and noticed “ears” on Saturn’s face – he couldn’t tell they were its rings!
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Saturn is a bit below the constellation of Leo right now, Leo the lion and moves so slowly it will be not too much farther to the left next year at this time!
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Now let’s look North.
Turn again to your left, and look for fairly high in the sky – about two outstretched hands above the horizon. Look for a rectangle of bright stars – that’s the cup of the Big Dipper. I’ll pause for a few moments and let you find it!
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Looking North in March and April, the Big Dipper is getting higher and higher in our evening skies, a bit to the right and above the north star, Polaris. You can use the top two stars of the big dipper’s cup to find Polaris. Draw a line from the top of the stars, named Merak and Dubhe, to the left. The next somewhat bright star you find along that line is Polaris! You’ve found your way North.
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Most people think Polaris is the brightest star in the sky – but it barely even cracks the top 50, actually! And at over 400 light years away, it’s dim only because of its distance, because the star is really more than 2500 times brighter than our Sun.
Well take a moment now to look around, and just enjoy the stars overhead. Remember that most of them stars have shown for years, and will continue to shine, sharing their light among the heavens, for hundreds of millions of years, and that relative to them, we humans are alive for a blink of an eye. And think how wonderful it is that we can know anything about them at all, through the science of astronomy, and the work of men and women around the world thousand and two thousand years.
That’s it for this month.
Please tune in again next month for the bright stars of April, when
we’ll see the brightest of spring stars, Arcturus,
taking its place above us. I’m Scott
Hildreth, from
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