Sometimes I’m surprised by something I thought I knew, and found out I didn’t, not really.
For your consideration: NGC 1427A, a dwarf galaxy.
[Click to unendwarfenate.]
I’ve seen pictures of this little guy before. It’s a small galaxy, maybe 20,000 light years across (the Milky Way is 5 times that size), and part of the Fornax cluster, a small but rich cluster of galaxies about 60 million light years away. The picture here was taken with the monster 8.2 meter Very Large Telescope in Chile, and uses filters that give a somewhat true-color appearance, though it also accentuates warm hydrogen (the pinkish glow).
Even though I’ve looked at it before, I don’t think I really saw it, because the boomerang shape is obvious, and to anyone familiar with galaxy dynamics the reason behind it is obvious too. Maybe it’ll help to know that this diminutive galaxy is screaming through the Fornax cluster at 600 kilometers per second, a ridiculously high speed.
See it now? NGC 1427A looks like it’s got a swept-back shape because it’s being swept back. In between galaxies there is an ethereally-thin fog of gas, but there’s enough there to have an effect on a passing galaxy. The boomerang shape of the galaxy is because that side is facing into the wind, so to speak, and being compressed. The pink curve in the image is due to rigorous star-formation going on there, where the gas clouds are collapsing from the pressure and birthing stars at a prodigious rate.
Looking at this image, it’s so obvious what’s going on I’m surprised I didn’t notice it before. I guess sometimes you miss stuff right under your nose if you’re not paying attention. If you consider 60 mega-light-years under your nose.
Tip o’ the Strömgren sphere to the ESO. Image credit: ESO. 10 extra BA points for anyone who knows what the title’s from. Don’t Google it! That’s cheating.
February 23rd, 2010 at 7:53 am
Strömgren sphere is the sphere of ionized hydrogen (H II) around a young star of the spectral classes O or B.
Oh, you mean the title? Err… I think that’s the name of the book written by Sir Patrick Moore, Chris Lintott, and Brian May.
February 23rd, 2010 at 8:01 am
Here at Irvine dwarf galaxies are a *HUGE* research interest. There’s an issue in astrophysics known as the “missing satellites problem”. Basically, there should be orders of magnitude more dwarf galaxies than what we see if you believe the Lamda-CDM model for the universe.
It could be they are there we just haven’t been able to observe them yet. (We keep finding them so this could be the case.) Or maybe there is new physics we don’t understand.
But, not knowing the answer is why it is a problem.
February 23rd, 2010 at 8:23 am
I just now checked out that “title” with Google…
February 23rd, 2010 at 8:33 am
The title is from an Abba song way back in ye olde 70′s. I think I have a vinyl LP with it around here somewhere. No record player though.
February 23rd, 2010 at 8:34 am
And thanks, now I have that song in my head.
February 23rd, 2010 at 8:39 am
Very beautiful. The dominate parts of it almost make it look like the Star Trek symbol
February 23rd, 2010 at 8:40 am
@ Evolving Squid,
You mean you actually bought that record, back then?!
What possessed you, man?!
February 23rd, 2010 at 8:43 am
I love the Hubble! Amazing.
February 23rd, 2010 at 8:59 am
ABBAmania. I thought everyone had an ABBA record back then. I think Arrival sold almost a million copies in Oz in ’76. Madness I tell you madness.
February 23rd, 2010 at 8:59 am
Hubble already got it 5 years ago:
http://hubblesite.org/newscenter/archive/releases/2005/09/image/a/
EDIT: the hubble heritage image is, the actual photo is from 2003.
February 23rd, 2010 at 9:03 am
BA: I think you made a mistake in your post. 600 kps is technically ludicrous speed, but just barely.
February 23rd, 2010 at 9:06 am
@ Shane,
Madness was one of my favourite bands, back in the late ’7os/early ’80s.
February 23rd, 2010 at 9:32 am
@Ivan3Man
Ditto. I was lucky enough to see Madness at the V festival in Oz last year. Not bad for old buggers too.
February 23rd, 2010 at 9:35 am
from the image it looks like most of the motion of the galaxy happens on the plane of the sky, but at those distances we can only measure radial velocities, not proper motions. How did we get the 600 kps figure? or is that just a lower limit?
btw, cool picture.. GO VLT!
February 23rd, 2010 at 9:39 am
It looks vaguely like the Star Trek badges. COINCIDENCE? I think NOT. Clearly God made this galaxy in this shape to test the faith of those who worship false idols. And by false idols I mean Jean-Luc Picard.
February 23rd, 2010 at 10:19 am
Notice the small reddish ring galaxy in about the 2 o’clock position from NGC 1427A!
There’s also a couple of what appear to be very faint nucleated dwarf galaxies to the right of NGC 1427A. Quite a interesting field.
Of course, NGC 1427A is most likely the result of a tidal encounter with NGC 1427 itself.
February 23rd, 2010 at 10:21 am
One of my college roommates was a big ABBA fan and would play their music over and over, so I’ve got it embedded in my neurons. It’s mostly dormant, but as soon as I saw the title of this post I knew I’d have that song running through my head for the rest of the day. Thanks so much.
Cool little galaxy, though.
February 23rd, 2010 at 10:43 am
Hooray for Abba!
And, oh yeah, cool turbo speed boomerang! What I wanna know is: Who threw it?? Wouldn’t mind having one of those to toss around out on the science quad.
February 23rd, 2010 at 10:48 am
ESO has a really great image of this object too, and both the faint dwarfs and the ring galaxy are visible (using the VLT): (http:) //www.eso.org/public/images/eso0627c/ . Both images are fantastic!
February 23rd, 2010 at 10:57 am
shawn #6 beat me to it, obviously proof of our future history of the galactic federation of planets…..
angus #15, i dont worship jlp, i only pray to him, i worship data, cause he’s obviously the supreme being
/waits for vulcans to make first contact
February 23rd, 2010 at 12:41 pm
I love how, at the forward edge you can see an offset between the blue (young, recently-formed stars) and the red (ionized gas around extremely young and still forming regions). So star formation first happened at the shock at the leading edge, then its gas got used up making new stars and the shock proceeds further into the galaxt where there’s still gas.
[TMB]
February 23rd, 2010 at 12:50 pm
How does one of these dwarf galaxies get moving so fast? Does it swing past a larger galaxy and get ejected into a different direction?
February 23rd, 2010 at 1:24 pm
Er, Phil, I think you meant “vigorous star formation” in your second-to-last paragraph, not “rigorous star formation.” Unless the stars forming there are doing so according to a particularly strict set of rules (more so than the laws of physics?!).
February 23rd, 2010 at 3:14 pm
I had a similar reaction to the images of the Bug Nebula published soon after Hubble’s upgrades. I’d seen pictures before, but never really focused on the fact that you can actually see the MOTION of the thing. Every since, I’ve been scanning new photos (frequently here) to see if I can tell how they’re moving. It makes pretty photos stunning to get some small sense of the dynamics involved.
February 23rd, 2010 at 3:26 pm
The scale of these things…just amazing. Here’s a little galaxy, one called a dwarf. It takes only a few hundred human generations for light to get across it.
I can’t imagine that. I trust that it’s factually correct, but I can’t imagine it.
February 23rd, 2010 at 5:48 pm
Re: “Even though I’ve looked at it before, I don’t think I really saw it…”
Well, you must admit it helps to have a view through an 8.2 metre VLT! Before you were probably looking at an image from a puny 5 metre scope (ahem).
This has got to be a new golden age for telescopes and astronomers.
February 23rd, 2010 at 10:01 pm
At 600 kps, I wonder – where is this galaxy going and why is it in such a hurry?
February 23rd, 2010 at 11:49 pm
@ ^ Bad Wolf :
Rushing to merger?
Gravity and the pull of other larger members of its cluster is probably the reason methinks.
If you consider 60 mega-light-years under your nose.
Actually I’d think its a lo-oong way *over* my nose.
Unless I’m looking at it through a telescope eyepiece in which case its just in front of and at about the same height as my nose!
February 24th, 2010 at 1:04 am
Turn it sideways and it looks more like Apollo’s “hand” from “Who Mourns for Adonais?”.
February 24th, 2010 at 4:17 pm
#15 Angus
“It looks vaguely like the Star Trek badges. COINCIDENCE? I think NOT. Clearly God made this galaxy in this shape to test the faith of those who worship false idols. And by false idols I mean Jean-Luc Picard.”
You Heretic – it was the Great Spaghetti Monster.
February 25th, 2010 at 8:30 pm
Yay! I’m not the only one who thought of obscure Abba songs when they saw the title!