Our Sun: The Corona

corona1.en.jpg

When we observe our sun’s corona, we discover something odd.

It’s really, really hot.

But…wait a second. How is that odd? Shouldn’t the sun be hot?

Well…yes. It should, and it is. Its surface temperature is almost ten thousand degrees Fahrenheit, and its core is many times hotter. But there’s a basic law of physics that says energy flows from hotter regions to cooler regions.

The core and photosphere (the visible surface) follow this rule. Even the chromosphere, the lower atmosphere, does as it’s told. But the corona is made up of gases that are hotter than the chromosphere.

What’s up with that? Continue reading

Infrared & High-Energy Astronomy

atmosphere.jpg

You probably recognize this image. You see something like it whenever you look up at the sky. Some days are clearer than others—some, you might even see a completely blue sky—but regardless, you know that this is an image of our atmosphere.

But do you know just how much your atmosphere does for you?

We’ll talk about how it protects you from space rocks later on. For now, consider the energy from our own sun. The sun doesn’t just send visible light our way—it operates in all wavelengths of the electromagnetic spectrum.

Some of those wavelengths are harmful, like gamma rays, X-rays, and ultraviolet radiation. Others, like infrared radiation, microwaves, and radio waves, are perfectly fine.

The atmosphere doesn’t really pick and choose which wavelengths get through to the surface. It blocks out some radiation it doesn’t need to. At least it protects us from the harmful wavelengths.

But that’s bad news for astronomers, because those wavelengths still contain useful information about the universe.

So how to we capture and analyze them? Continue reading

The Hubble Space Telescope

hubble.jpg

The Hubble Space Telescope is one of the most famous telescopes in the world.

Oops, excuse me—one of the most famous telescopes built.

Hubble, after all, is certainly not in this world. Unless you call the universe the “world,” it’s about as far from being in this world as you can get. It’s in space.

Hubble isn’t that different from an ordinary, ground telescope. It’s only as big as a bus. There are bigger optical telescopes. Its mirror is 2.4 m across—hardly an achievement by modern-day standards.

Palomar Observatory, which was the biggest telescope in the world when it was built, has better optics than Hubble, meaning its images are a bit crisper.

But that doesn’t keep astronomers from continuing to use Hubble. In fact, if you want to use Hubble, you have to get in line—it hardly has time to complete all the projects astronomers ask of it, even observing the night sky 24/7.

So why is Hubble so useful? Continue reading

Radio Astronomy: Advantages

arecibo.jpg

Whoa…what’s this thing?

It’s a radio telescope, the largest in the world. It’s so huge that a normal support system can’t support its weight. So it’s basically suspended between three mountaintops. It’s 300 m across, which is 1000 feet. It’s huge.

This is the kind of construction endeavor that radio astronomers must try if they want to get much detail from radio waves. The radio wavelengths of the electromagnetic spectrum are really, really weak. You need huge telescopes to collect enough.

But, as ever, astronomers face the same basic problem: money.

Huge telescopes are expensive. It’s unfortunate for astronomers, but true—just think of the cost of labor of basically burying a whole valley under a radio dish.

So why bother? Continue reading

Radio Astronomy: Limitations

radio astronomy.jpg

Astronomy is a labor of love, and radio astronomy is no different.

As I covered in my last post, radio astronomy deals with the longest wavelengths of the electromagnetic spectrum (a spectrum that includes visible light). Radio waves are not sound waves. They’re radiation just like visible light, infrared, and ultraviolet.

I’ll prove to you that radio waves can’t be sound waves. We get them from space—that’s why there’s such a thing as radio astronomy. But there’s no sound in space. Why? Sound requires something to pass through, and space is a vacuum.

So, we’ve established that radio waves are just another form of electromagnetic radiation. And astronomers love to collect any form of electromagnetic radiation. We can’t touch the stars ourselves, so it’s our only chance at learning about the cosmos.

Why? Because just about everything in the sky emits electromagnetic radiation.

Everything except black holes and a couple other things…but those are topics for another day.

But electromagnetic radiation isn’t easy to collect. And radio waves are especially hard. Continue reading

Radio Astronomy

radio scope.jpg

Ever seen one of these before?

Yeah, it’s a bit bigger than your average radio antenna.

That’s because its job isn’t to direct radio signals to your house. It’s a radio telescope, and its job is to collect as many radio signals as it possibly can—from outer space, not from a radio station.

Radio astronomy is a tricky business. It has its advantages over visible astronomy—it certainly works better for interferometers—but radio signals are so weak, they’re hard to detect and study. Which is why you’ll never see a small radio telescope.

So, how do astronomers manage to collect and study radio emissions from the cosmos? Continue reading

Info in a Rainbow

milky way.jpg

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

Telescope Imaging Systems

sombrero galaxy visible.jpg

Have you ever seen an image like this?

Okay, maybe you have…online. What with the spread of the internet these days, I’m guessing that at one point you have seen something like this on a page of image search results.

That’s the thing, though. You’ve seen this incredible phenomenon on a computer screen. But have you ever seen it through a telescope?

Don’t worry—if you haven’t had an opportunity to look through a telescope, you’re not missing out. You’re not going to see the Sombrero Galaxy above in all its photographed glory just from looking through the eyepiece of a telescope.

So…how do we get an image like this, then? Continue reading

Interferometry

Double-stars-Rayleigh-limit-ST

Imagine you have an image like this. This object is faint and faraway, so you can’t make out much more detail. You know that other stars like it—closer, brighter stars—have looked like this and turned out to be two stars, nestled very close together.

How do you figure out what you’re looking at? How do you increase the resolving power on your telescope so that you can make out more detail?

A telescope’s resolving power is limited by its size. Bigger telescopes can make out more detail on faraway objects—that’s because they can gather more light. But now, we can make telescopes that are so big their size doesn’t limit their resolving power anymore.

The atmosphere does.

We obviously can’t change the atmosphere. So how do we get around this particular predicament? Continue reading

Improved Telescope Mirrors

e-elt.jpg

When it comes to telescopes, bigger is always better.

Bigger means more light-gathering power and better resolution. And a longer telescope—meaning, a longer focal length—can actually do wonders for your magnification power.

Light-gathering power, by the way, just means how much light a telescope can gather—and it works the same way as rain in a bucket. The bigger the bucket, the more rain you can collect.

And resolution means how much detail you can see in an image. It goes hand in hand with light-gathering power—more light means more detail.

So bigger, for serious astronomers, is the way to go. Until your mirror starts sagging.

Yeah…that’s a bit of a problem. But nowadays, we can fix it. Continue reading