Barred for life

The entire universe in blog form
April 3 2007 6:16 PM

Barred for life

It's been a while since I posted a pretty picture just to post it. Click it for a bigger version (or go here to get a choice of images, including a monster image at 48 meg!).

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  


Of course, I can't just leave it at that! Astronomy is so much more than just pretty pictures.

There's a lot to see in this image, the latest release form Hubble. It's NGC 1672, a barred spiral galaxy (NGC stands for New General Catalog, as my last real episode of Q and BA notes). All by themselves, normal spirals are weird enough. We know that stars closer in to the center revolve around the core of the galaxy faster than stars farther out, so that tells you right away that arms are not just bands of stars. If they were, they'd wind up tighter and tighter with time, and they wouldn't last very long (I'm surprised I haven't seen any creationists use that as an argument against an old Universe).

So what are they? Turns out, the best hypothesis so far is that they are standing waves, like cosmic traffic jams. If you were in a helicopter over a traffic jam on the freeway, it would look like the jam is a permanent fixture of the traffic. But in reality, cars leave the jam at the same rate as cars entering it. So while the jam itself stays put, the cars making it up always change. So it is with spiral arms: they are places where the matter in the galaxy is compressed, but stars enter the jam and stars leave. The arm looks permanent, but over time its resident stars, gas, and dust change.

Weird, eh?

But of course, things always get stranger. NGC 1672 is a barred spiral. The big arms don't go all the way to the center; they seem to emanate from the ends of a rectangular structure. The bar here isn't as obvious as in some galaxies (like, for example, our own Milky Way), but if you look at the high res version of the image you'll see it better. Bars are really weird, and are a result of the complicated gravitational forces due to an extended mass like a galaxy. The gravity from individual objects is easy to understand -- the farther you are from them, the weaker you feel their gravity, and so on -- but when you take a few hundred billion masses and spread them out into a disk, things get messy.

In such a situation, I'd go to a bar too. Haha. Heh.

Perusing the very high res images, you can see just what a mess things are. Gas and dust are strewn everywhere, stars scattered like dandelion seeds in the wind... people who study such things have their work cut out for them. But for you and me, we can simply scan the image and look for interesting things. Foreground stars -- ones in our own Galaxy -- blaze out. Fainter, more distant galaxies can be seen right through NGC 1672 (I love that). Pinkish clouds denote regions where stars are forming; stellar nurseries. These really define the arms of the galaxy; massive stars are born, and outshine all the other stars. These stars are blue, giving the arms their bluish hue. They don't live long enough to pass out of the arm; that takes millions of years; time the stars don't have. They explode before then, becoming supernovae, and scattering their elements back into the galaxy from which they came.

It's the cycle of life, but on a somewhat larger scale than here on Earth.

I said above that astronomy is much more than pretty pictures, but actually, there's a whole lot you can learn from simply looking over images like these. I've barely scratched the surface here. Still, it is pretty. Sometimes, as I've said many times in the past, that's enough too.



Talking White

Black people’s disdain for “proper English” and academic achievement is a myth.

Alabama’s Insane New Abortion Law Gives Fetuses Lawyers and Puts Teenage Girls on Trial

Tattoo Parlors Have Become a Great Investment

A Jaw-Dropping Political Ad Aimed at Young Women, Apparently

The XX Factor
Oct. 1 2014 4:05 PM Today in GOP Outreach to Women: You Broads Like Wedding Dresses, Right?

Big Problems With the Secret Service Were Reported Last Year. Nobody Cared.


Operation Backbone

How White Boy Rick, a legendary Detroit cocaine dealer, helped the FBI uncover brazen police corruption.

Hong Kong’s Protesters Are Ridiculously Polite. That’s What Scares Beijing So Much.

This Gargantuan Wind Farm in Wyoming Would Be the Hoover Dam of the 21st Century

Oct. 1 2014 8:34 AM This Gargantuan Wind Farm in Wyoming Would Be the Hoover Dam of the 21st Century To undertake a massively ambitious energy project, you don’t need the government anymore.
  News & Politics
Oct. 2 2014 11:01 AM It Wasn’t a Secret A 2013 inspector general report detailed all of the Secret Service’s problems. Nobody cared.
Oct. 2 2014 12:58 PM Why Can’t States Do More to Protect Patients From Surprise Medical Bills? It’s complicated.
Lexicon Valley
Oct. 2 2014 1:05 PM What's Wrong With "America's Ugliest Accent"
  Double X
The XX Factor
Oct. 2 2014 12:37 PM St. Louis Study Confirms That IUDs Are the Key to Lowering Teen Pregnancy Rates
  Slate Plus
Behind the Scenes
Oct. 1 2014 3:24 PM Revelry (and Business) at Mohonk Photos and highlights from Slate’s annual retreat.
Brow Beat
Oct. 2 2014 1:29 PM Want to Know What Makes David Fincher Great? Focus on What He Doesn’t Do.
Future Tense
Oct. 2 2014 1:22 PM If Someone Secretly Controlled What You Say, Would You Notice? What cyranoid experiments reveal about how people act.  
  Health & Science
Oct. 2 2014 12:53 PM The Panic Virus How public health officials are keeping Americans calm about the Ebola threat.
Sports Nut
Oct. 1 2014 5:19 PM Bunt-a-Palooza! How bad was the Kansas City Royals’ bunt-all-the-time strategy in the American League wild-card game?