Stars don’t look small because they’re really the size of pinholes in a blanket. The smallest are the size of Earth. The largest have 128,865,170 times Earth’s diameter.
They look small in the sky because they’re distant. It’s for the same reason you can tell how far away your surroundings are by how small they appear; you know the mountains on the horizon are far away because they look shorter than your house.
The nearest star to our solar system is 4.3 light-years away. But what exactly is a light-year?
Light seems to travel instantaneously from your flashlight to the nearest surface, but it actually has a finite speed. In one second, it travels 299,792 km—fast enough to wrap itself around Earth’s equator 7.5 times.
In one year, light covers 9,460,730,472,580.8 kilometers, enough to wrap around the sun’s equator 2160.5 times. Four times that is the distance to the nearest star.
But how do we know this? Continue reading
There are 250 billion stars in our galaxy alone. Many are much like the sun, labeled with the Latin sol for “sun” in this diagram. But many more are not quite what we might expect stars to be like, after living under the light of a white G2 star our whole lives.
Wait a second. White G2? Since when is the sun white? And what the heck does G2 mean?
I’m talking about its spectral type—a classification system that organizes stars by their temperatures, determined by what they’re made of. The sequence is O, B, A, F, G, K, and M, in order from hottest to coolest. The sun is a fairly cool star.
But the thing is, the spectral types don’t actually tell you anything about how bright the star is, how big it is, how luminous it is…I could go on.
So how can we make things easy for ourselves and classify stars according to spectral type, size, and luminosity all at the same time? Continue reading
Find yourself a dark, unpolluted night sky on a clear night free of clouds, and you are very likely to look up into the heavens and see a sight quite like this. It’s what we see of the Milky Way, our galaxy.
When I’m at an astronomy event with a sky like the one above, I find it absolutely incredible. Do you notice how the stars don’t all look the same?
A couple are startlingly bright, there are numerous stars that are somewhat dimmer, and if you look really hard, you notice that even the dark night background is sprinkled with stars so faint they can barely be seen.
But what if I told you that you’re not even seeing the half of it? Continue reading
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 are hot.
Really hot. Hot enough to have energy to spare for their planets. If our star wasn’t hot, we couldn’t live on Earth. And our star isn’t even particularly hot for a star. It’s a middle-aged star of low mass, so it’s relatively cool compared to other stars.
You might also notice that stars aren’t all the same color. There are redder stars and bluer stars and more whitish stars.
We know stars are hot. They’re also bright. And they’re different colors. But how does that all translate to radiation—and how can we see it? Continue reading
What do you see in this image?
If you’re from a larger city and haven’t had the opportunity to venture into a place like the desert, you might not know what you’re looking at. That’s the Milky Way, our name for our galaxy.
Inside this galaxy are billions of stars, including our own. Galileo Galilei was the first to discover that it was really many tiny points of light, not just a cloud-like haze across the dark night sky.
We can’t see our galaxy from outside, but we can learn a lot about it by looking out at it from within. It’s difficult. It’s like trying to learn about a building if you can never step outside one of its rooms.
But we can do it, with the help of the spectrograph. Continue reading
When you hear about “space-time,” it’s just a way to say that space is related to time. And the curvature of space-time, as Albert Einstein predicted, is the way space and time alike literally bend around a mass such as the Earth or the sun.
That’s what’s diagramed above. This is a three-dimensional concept diagram of the way space sort of “clings” to an object. Notice the way it sort of tightens up when you get close to Earth? And because time is part of this whole equation…time sort of tightens up, too.
I assume that explains the “twin paradox,” as it’s called. That’s where the space-traveling twin returns home to Earth younger than their Earth bound twin.
Why? Seems to me it’s because time was tighter and passed faster on Earth, while it spread out and passed a bit slower for the traveler. (Don’t quote me on that, I just guessed that from this diagram.)
Einstein figured all this out. But scientists need evidence. Trusting Einstein’s genius wasn’t enough for them. How did they accept relativity as fact? Continue reading
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