Doppler shift
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How Massive are Galaxies?
If you needed to measure the mass of, say, a brick — or some other Earthly object — you could just set it on a scale. (Yes, scales measure mass, not weight.) With galaxies, it’s not so easy! I don’t…
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What are Planetary Nebulae?
Meet the planetary nebula, one of the universe’s most gorgeous phenomena. If you’ve ever looked through a telescope, you may have seen one of these before. Through a small telescope, one might look like a little planet — hence the…
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Observations of Star Birth
Astronomers have a pretty solid idea of how stars are born. They begin within the dense, cold dust of an interstellar cloud such as this one. They heat up and get more luminous as they contract, and then drop in…
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What Makes a Star Blue?
Albireo is the distinctive double star in the head of the constellation Cygnus. You can find it yourself if you look for the Summer Triangle amid the dusty trail of the Milky Way across the night sky. The brighter, orange…
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Stars and Proper Motion
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…
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Our Sun: Helioseismology
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…
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Our Sun: The Photosphere
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…
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The Doppler Effect
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…
