The Universe Needs A Speeding Ticket!

One topic astronomers don't talk about very much is how fast things move in outer space.  I'm sure most of you reading this have either driven a car or taken a ride on a roller coaster and felt how fast ~60mph is. You're hair's blown back, your face forced into a smile, trying not to scream as your flying down the roller coaster hill. It's really fast from a human perspective! Yet believe it or not, you're actually moving much faster than that all the time, and you don't even realize it! Everything in the universe is moving, including Earth, the Sun and the Milky Way. Below is a list of speeds (in miles per hour) that these objects are moving at, just to put things into perspective….

• The Earth spins on it's axis at a speed of 1,040 mph
• The Earth orbits around the Sun at 66,615 mph
• The Sun and our solar system orbit the center of the Milky Way at 447,387 mph
• Our Milky Way galaxy and the Andromeda galaxy are hurling towards each other at 310,685 mph
• The universe is expanding at a rate of ~180,000 mph

And you thought airplanes and rocket ships moved fast! Now do you agree with me that the universe needs a speeding ticket?!

Why Is Space Black?

I think everyone at some point has looked up and asked "why is the sky blue?" , and if you go to the week of 3/27/11 in the archive you can find the answer! But have you ever looked up at the night sky and wondered why is the sky black? Well duh! It's because your not facing the sun, which lights up the sky during the day, right? Well, not exactly….

Think about this. The Universe is huge! Our galaxy is filled with hundreds of billions of bright stars, and the universe is filled with billions of bright galaxies. In every direction we look, there are bright sources of light, and this light has been traveling towards earth for over 14 billion years. So we would actually expect the night sky to be beaming with light from stars and galaxies! But obviously it's not, so what's going on? Any guesses?

Ok I'll tell you. The fact that the night sky is black is proof that our universe is expanding!  What's happening is that as the universe expands, objects move away from us. The light emitted by these objects is Doppler shifted, which means it's shifted towards the "Red" part of the electromagnetic spectrum. The faster it moves, and the farther away the object is, the more red the object looks. Many of objects in the night sky are either so far away that they are too faint to be seen with the naked eye, or their light has been red-shifted into a part of the spectrum that our eyes are not sensitive to!  And that is why we don't need "star-glasses" at night!

 Image Credit: DeviantArt: ~andrei030

The Electromagnetic Spectrum (aka light)

Astronomers use electromagnetic radiation (fancy word for light) to study astronomical objects. Light can come in many varieties. There is visible light, which we see with our eyes, but there is also other types of light that human eyes are not sensitive to. For example, when you go to the hospital to have an x-ray, your body is exposed to x-ray radiation. Night vision cameras allow you to see infrared radiation, which is essentially the heat given off by different objects. The image below shows you all the different types of light, what wavelength and frequency they have, and compares the size of the wavelengths to a common object. 

 

 

It was not long ago that astronomers realized that outer space glows in more than just visible light. With special cameras mounted on telescopes, astronomers can see how objects look at any light wavelength they choose. And boy were they surprised at the results! Below is an image of the cartwheel galaxy. On the right hand side is the galaxy in the x-ray, Ultraviolet (UV), visible, and infrared (IR) wavelengths. The big picture is a combination of all these pictures. 

  As you can see, the galaxy looks very different in each of the four different types of light. You can't really tell that the object is a galaxy in the x-ray, but in the visible and IR, three galaxies are visible! This use of the whole electromagnetic spectrum allows astronomers to study outer space in new ways and discover things that were "not visible" just 30 or so years ago!

Image credit (bottom):  Chandra, GALEX, Hubble, Spitzer - Composite: NASA/JPL/Caltech/P.Appleton et al.