Originally posted October 26, 2010

And boy are my photons tired

October 26, 2010

Not just tired … but really, really faint. And waaaaaay red-shifted (more on this in a minute).

Some how, some way, astronomers have found a galaxy 13.1 billion light years away. (A light year is just the amount time light travels in a year). That means that for light from this galaxy to reach us, it has had to travel approximately 77,000,000,000,000,000,000,000 miles! I have a hard time even understanding what that number means. I think most people would agree with that sentiment, which is why astronomers use light years, which is much more reasonable, which in this case comes to 13,100,000,000 light years, which really makes the distance more approachable, really(?), doesn’t it, OK. Let’s just say this galaxy is old. It’s older than that T-shirt your wife keeps asking you to get rid of. It’s older than your Grandma Millie. It’s older than the hills. It’s older than dirt. It’s the oldest thing we’ve ever seen. It’s pretty friggin amazing.

World’s oldest galaxy … Oooops … world’s oldest dog. Isn’t he cute!

Can you see it. That little smudge. It’s right there. Can’ miss it! It’s the world’s oldest galaxy (at least for now) as described in the journal Nature here and here (subscription required). The discoverers have given this galaxy a nice, long, boring scientific name but have lovingly dubbed it: “the high red-shift blob”.

So (channeling my inner- Seinfeld), “What’s the deal with this red-shifting? Who are the ad wizards who came up with that one?” Well thanks for asking, Jerry. A train whistle changes it’s pitch as it moves away from you (red-shifting). Super-Doppler-Radar-Weather tells you if that storm will bypass your picnic (red-shifting). Actually red-shifting is more of a Doppler-thing than Doppler being a red-shift thing. The Doppler effect stipulates that if a light source (star/galaxy) is moving away from you, it will appear redder than it actually is.

How red-shifting works. Stars moving away from us look more “red” than they would normally look. The black lines on this figure indicate the specific colors of light produced by a star. As the universe expands, and the star moves away from us, the light produced appears to be “redder”.

The cool thing about red-shifting is that if astronomers can figure out how fast an object is moving away from us, they can use the red-shifted color of the star’s appearance to figure out how far away it is. (Isn’t science fun!?) Using a calculation based on the physics of red-shifting (that was the easy part) and some other more in depth observations and calculations (the more difficult part), the astronomers heading up this research pinpointed the distance between “the high red-shift blob” and us with pretty good accuracy.

Aside from its age, the work on “the high red-shift blob” tells us a lot about how the universe, as we know it, formed. This galaxy was formed at about the earliest period of time (after the big bang) that any galaxy could form. This research also tells us about how the universe changed forms 600 million years in. “The high red-shift blob” is surrounded by a bubble of plasma (think aurora borealis) amid a sea of gas (think, um, whatever you like). That plasma bubble (and similar ones like it from other galaxies) eventually overtook the sea of gas and left us with a universe that looks an awful lot like the one we have now.

We get to learn all of this from a lucky find, a couple hours on a telescope, and some hard-core physics.

To answer my previous question, “Yes. Science is very fun!”

-mrh