The True Brightness of Stars

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Have you ever looked up at the night sky and noticed that while relatively bright stars outline the constellations, there are numerous other stars that are almost too faint to see with the naked eye?

If you ever noticed this, you probably guessed that the brighter stars are literally brighter, and the fainter stars truly are fainter. Or maybe you guessed that they don’t vary in brightness that much, but fainter stars are much farther away.

But that’s not really true…or, at least, it’s not the whole answer.

So what’s the real reason why some stars appear to be brighter than others—and how can we tell how bright they really are? Continue reading

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

Stars: Naming and Brightness

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Meet Pegasus, and the constellations surrounding it. As I said in my last post, constellations are just regions of space.

Yes, they are named after mythical beasts and ancient queens, but for scientific purposes, all that matters are the regions they denote.This way, astronomers can easily find obscure, faint objects in the sky.

And telescopes can be easily programmed to find the same objects for those with less experience.

Keep in mind, though, that constellations only appear to fall in the same horizontal plane over Earth’s surface. Some of these stars, even in the same constellation, are light-years apart from one another.

So, in that case, the brighter stars must be closer to us and the dimmer stars farther away, right?

Wrong. Continue reading

The Ecliptic

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The ecliptic, as astronomers call it, is the apparent path of the sun against the background of the stars in the sky.

It’s useful because it tells us how to find the planets in the sky. They can be hard to spot if you don’t know where to look, but they will always be somewhere along one imaginary line that arcs across the sky—the ecliptic.

This pattern never changes. The planets don’t follow the ecliptic exactly, but it’s useful for getting an idea of where they should be.

But why does it work—and what exactly does it mean, when it’s obvious we can’t see the sun among the stars of the night sky? Continue reading

Mapping the Sky

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I need you guys to help me with something.

Can you find a horse in this image of the night sky?

Yeah, me neither. I’m lost. I see the Great Square of Pegasus because I know what to look for, but I still don’t see a horse.

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Okay, so now I see half a horse. Where’s the rest?

Your guess is as good as mine, guys. Truth is, constellations very rarely look like what they’re named after. Constellations are more like relics of our ancient past than actual descriptors of what we see up there in the sky. But they do serve a purpose, even if that horse up there is missing his back legs.

I really find myself wondering if whoever made up Pegasus was concerned with animal rights… No animals were harmed in the making of this sky map…

Okay, yeah, never mind.

Where was I? Ah, that’s right. The purpose of the constellations, and the reason why it really doesn’t matter if they don’t look like their names say they do. Continue reading