Stars and Proper Motion

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Recognize this constellation?

Well, at the time stamp of about 2000 AD (CE), I think you will. It’s one of the most famous constellations in the night sky.

Well, technically, it’s not a constellation at all.

It’s an asterism—a commonly recognized grouping of stars that isn’t actually official as a constellation. There are tons of asterisms that you no doubt recognize…the Summer Triangle, the Great Square of Pegasus, the Big Dipper.

That’s right. That mess of stars up there that keeps changing for some reason…that’s the oft-recognized Big Dipper, part of the constellation Ursa Major.

So why the heck are the stars moving? Continue reading

Our Sun: Helioseismology

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We can’t see below the surface of the sun.

That makes sense, really. We can’t see below the surface of the Earth, either—we have to get creative if we want to find out what goes on below the crust.

In the sun’s case, we can’t see below its photosphere because the gases within are so dense, light can’t escape. And we depend on light to see anything.

So…if we can’t see inside the sun, how do we study it? Continue reading

Our Sun: The Photosphere

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Recognize this?

You might, if you’ve ever seen the sun through a telescope before. What you’re seeing is the photosphere, the layer of the sun whose light reaches Earth. This is the only layer you’ll ever see, without the aid of a solar eclipse.

Wait a second…what do I mean, layers? I mean, I know what a layer is, but what kind of layers does the sun have?

Well, it’s got a few, just like the Earth. Continue reading

The Doppler Effect

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Have you ever heard the ice cream truck?

When I was little, I remember hearing the ice cream truck all the time. Just the sound of the opening notes of “Pop Goes the Weasel” were enough to propel me to the door, where I’d beg my parents to let me go out.

Of course, I didn’t always make it out front in time. But one day, my dad found a way to solve that problem—by actually getting in the car and chasing the ice cream truck.

I remember us driving around the neighborhood, following that white truck around. A few times, it slowed and stopped, but when we stopped too, it kept going again. It took a while for the driver to realize we were following him!

Eventually, we caught it, and had a good laugh over it. But the moral of the story is…have you ever noticed that you can tell if something is moving toward you or away from you, just by if it’s getting louder or quieter?

The same trick works for stars…sort of. Continue reading