How many galaxies can you handle today?
I hope it’s a lot. Because I have three to show you, or maybe 5, depending on how you count them.
First off, a gorgeous trio of interacting galaxies courtesy the Hubble Space Telescope. This group was the winner of the contest to have people vote on where to point Hubble:
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| Click this and the other pictures to get to embiggenated ones. |
This group of three galaxies together are called Arp 274; Halton Arp cataloged quite a few oddly shaped galaxies, suspecting that they were more interesting than you might suppose at first glance. He was right; almost all the entries in his catalogue are galaxies interacting with one another, their mutual gravity distorting their shapes, their massive collisions triggering vast bursts of star birth across hundreds of thousands of light years of space.
It’s not clear what’s going on in this trio, located 400 million light years away. The two galaxies on the right and left are clearly undergoing massive star bursts, which can be seen as the large blotches of blue (when lots of stars are born, some are very massive and very luminous ones; these shine blue… and while they’re vastly outnumbered by lower mass redder stars, the dinkier stars shine more feebly and are harder to see).
The middle galaxy, however, appears relatively undisturbed. Oddly, it also seems to be at a different distance from the other two, as measured using its redshift (how fast it’s apparently moving away from us). Is it possible that the middle galaxy is merely superposed on the other two, and it’s just that pair that’s interacted sometime in the past? Or does the middle galaxy have an anomalous velocity for some unknown reason? Poking around the journal papers, I was unable to find an answer. That in itself is interesting!
The next two galaxies are from the European Southern Observatory. The first of these two is also a spiral, but a bit of a mess: NGC 7793, 12.5 million light years distant.
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This photo, taken with the monster 8-meter Very Large Telescope, shows off the chaotic nature of this spiral. Most big spirals have well-formed spiral arms, but this one is a disaster. Why? Interestingly, it has a lot of gas in it, one of the largest supplies of hydrogen known in any normal galaxy. It’s also forming lots of very massive stars, so many that the gas is largely ionized (that is, stripped of electrons by the ultraviolet light from the stars) throughout the whole galaxy. Does this affect how the spiral arms form? It’s hard to say, but when you have two weird things in one place, it’s tempting to correlate them. It’s also not a terribly big spiral, less than half the diameter of the Milky Way. Does that play in to this as well? Again, it’s hard to say.
The last galaxy is NGC 55, an irregular, elongated galaxy. It’s flattened and we see it roughly edge-on:
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This image was taken by the 2.2-meter MPG/ESO telescope in La Silla, Chile. NGC 55 is pretty close by, only 7.5 million light year away, maybe three times as far as the Andromeda Galaxy. It’s a bit of a mess, but its proximity gives us a great look at it. In this image, individual stars can be seen! We can also pick out planetary nebulae; giant shells of expanding gas blown off by dying stars. The properties of these nebulae can be used to figure out how far away they are from us, which gives us the distance of the galaxy itself. It’s an irony of nature that it’s easier to figure out the distance to remote galaxies, which are swept away from us by the expansion of the Universe itself, than it is for nearby galaxies, which are too close to use the cosmic expansion for distance.
NGC 55 is a bit like the Large Magellanic Cloud, an irregularly-shaped galaxy that orbits the Milky Way; both are oddly shaped, both are somewhat flattened. But NGC 55 is hugely larger than the LMC, perhaps five times as big. We’re not sure why some galaxies are irregular, and why some of these weirdos do have some shaping involved, like why being flattened.
Galaxies are huge, beautiful, intensely studied, and yet they still hold many mysteries for us to investigate. Even ones that are nearby — if you call quintillions of kilometers "close"! — and big in our telescopes still hold their secrets. But it’s images like these that will help us understand them better, and slowly unravel the tapestry of how these gorgeous objects behave.
April 4th, 2009 at 11:22 am
That God…always littering in the sky. Tsk tsk.
April 4th, 2009 at 11:24 am
Thank you! These are beautiful. =]
April 4th, 2009 at 11:31 am
Okay, I don’t know anything about anything, so I’m going to ask for some help looking at the pictures. Sorry that I’m stupid. In the last galaxy, how can you tell which stars are in the galaxy and which ones are superimposed on it? And where are the planetary nebulae?
April 4th, 2009 at 12:03 pm
Arp 274 is such a cromulent group of galaxies.
April 4th, 2009 at 12:04 pm
Those are great. I voted for that first one on hubblesite.
April 4th, 2009 at 12:25 pm
I am pleased to say that I voted for that image. Big giant collections of hundreds of billions of stars crashing into each other appeals to me.
April 4th, 2009 at 12:53 pm
Simply beautiful!
April 4th, 2009 at 1:03 pm
Bring it on! I can handle lots more galaxies! Hubble and ESO are real artists though.
April 4th, 2009 at 1:12 pm
“almost all the galaxies in his catalogue are interacting with one another”
I know what you mean, but that’s not what it says.
Nice post, though.
April 4th, 2009 at 1:19 pm
NGC 55 is part of our Local Group, IIRC… Kewl! I wonder if it has little spiral arms which we’re seeing edge on…
April 4th, 2009 at 1:23 pm
God point Pieter; I fixed the grammar. Thanks!
April 4th, 2009 at 2:05 pm
Zooming in is SOOO cool! I wish I had a space craft with an instantaneous probability drive, then I could go check these out in person. Ah well, I guess I’m stuck with this time travel view,,,
Great pics, Phil.
Thanks.
GAry 7
April 4th, 2009 at 2:23 pm
oh my god! it’s full of stars!
April 4th, 2009 at 2:32 pm
If the supreme court would legalize it, I would marry the HST. I loves me some galaxies! Gorgeousness and gorgeosity made real.
BTW, I suppose there’s slim chance the one in the second picture is actually a spiral right smack in front of an irregular? I guess the large quantity of hydrogen would rule that out, huh?
April 4th, 2009 at 2:39 pm
Oh, sweet mysteries of space, at last I’ve found you……
J/P=?
April 4th, 2009 at 2:54 pm
Phil,
Spitzer just released a new infrared image(/mosaic) of M33 on Friday:
http://www.spitzer.caltech.edu/Media/releases/ssc2009-08/ssc2009-08a.shtml
I’m one of those lucky few (who found the ad for the lecture, that is) who saw it _days_ before the rest of the world. OK, it was ~1.6667 days before, but still — that’s worthy of an evil cackle or two, so bwahahahahaa!
April 4th, 2009 at 2:59 pm
Sweet photos, Phil! I’ve got a minor nitpick, though; from what I understand, the LMC is *not* orbiting the Milky Way. Newer, more accurate measurements of its speed peg it above the escape velocity of our galaxy. My name links to a 2007 press release with the details.
April 4th, 2009 at 4:27 pm
For the space love’n crowd, here are two collections I like to share:
http://picasaweb.google.com/sirald66/WONDER
http://picasaweb.google.com/sirald66/ForMCC
April 4th, 2009 at 4:56 pm
Cool! First time encounter. Remind me. What’s the nearest approach the LMC or SMC has been or will be to the Milky Way?
GAry 7
April 4th, 2009 at 5:12 pm
Beautiful pictures, especially the first and last ones.
How come we don’t know how irregular galaxies are created? What theories are there? For example that an irregular galaxy can formed when two galaxies merge, or just fly by each other and stretch each other through gravity. Or maybe that unequally distributed dark matter is the reason.
April 4th, 2009 at 6:14 pm
Link to the ESO gallery picture of the middle one is broken.
April 4th, 2009 at 6:57 pm
To paraphrase the old Sam Cooke tune – Don’t know much about Astronomy. I enjoyed both the photographs and the explanations.
April 4th, 2009 at 7:28 pm
Halton Arp cataloged quite a few oddly shaped galaxies
Was he trying to find evidence of a Plasma Universe?
April 4th, 2009 at 7:47 pm
Absolutely beautiful.
April 4th, 2009 at 8:50 pm
Essential here is a plug for Galaxy Zoo (https://www.galaxyzoo.org/) where anyone can look at all the galaxies they can handle. You can help classify them, or you can just go into the forums and browse posts about weird and wonderful galaxies.
April 4th, 2009 at 9:54 pm
Nice pictures!!
I’m now taking a galaxy course at university, and we’re currently talking about galactic dynamics. There are lots of mysteries about galaxies formation.
I’ll share this post with my classmates.
Thanks for the images!!
April 4th, 2009 at 11:22 pm
To Katie:
I would guess that any star you can make out in the 3rd image is a foreground star in our own galaxy. To answer your next question; Any planetary nebula in that distant galaxy would be very small and dim. I don’t even know if a planetary nebula has ever been imaged in a galaxy outside of the Milky Way. Phil?
April 5th, 2009 at 6:31 am
wow. Preeeeeeety.
April 5th, 2009 at 7:17 am
I am intrigued by the differing spiral patterns of the two larger of Arp274 galaxies. Why should those two spiral shapes differ? You imply that the difference is due to interaction of two proximate galaxies. At the same time, I am bewildered to believe either of the two hypotheses: The first is that such spirals are the path of stars descending into a large mass or black hole. The other hypothesis is that these are instead a trail of stars being expelled from a central mass. Could it be that both can occur? If so, then one can ascribe the largest spiral, with the most consistent path as the descending trail. The next smaller spiral can be ascribed to be the result of emission of matter and new stars from another central mass. That the former is feasible seems apparent from its compliance with known spiral paths where the trajectory is only controlled by conservation of momentum, and the density having been that of a unified cluster of stars being pulled in. The latter spiral density is controlled by the ejection cycle of that mass source, while the radius is controlled by the ejection velocity which can vary throughout that ejection cycle. Yet another possibility, as you infer, is that the second spiral was affected by the earlier passing of another galaxy, perhaps the third, past the trail or cluster of stars that was heading toward that central mass, some of that trail having been deflected or delayed, resulting in the “bent” arm of the second spiral. The jury is still out, apparently.
April 5th, 2009 at 11:34 am
Embiggenated? Really?? I couldn’t even read the rest of this article.
April 5th, 2009 at 12:28 pm
Grammar Nazi, here’s an idea: loosen up.
April 5th, 2009 at 12:41 pm
Yeah, Grammar Nazi, “loosen up” like Phil is doing to the English language(!).
April 5th, 2009 at 1:32 pm
Hey, Ivan,
Phil is a poet and as every poet knows, we get to masticate our preferred language any way we wish, since the language is ours to command.
That’s evolutionary philology in action,,,(Ok, so, that’s a loose use of the term)
Gary 7
April 5th, 2009 at 2:42 pm
Beautiful pics Phil. Do you think astronomers on any planet in that mass of confusion would ever be able to conclude that they were in a collision?
Cheers
April 6th, 2009 at 12:36 am
Excellent post, Phil. Also, another plug to go to http://www.galaxyzoo.org to help them classify a million or so galaxies. It’s quite fun and very helpful to the Sloan Digital Sky Survey. They are gleaning some very useful data out of having non-astronomers try to classify galaxies using a few basic visual parameters.
Here’s some fun I have had with the extreme hi-def TIFF files of galaxies from Hubble. It’s called “look at the galaxies behind the galaxies:”
http://tispaquin.blogspot.com/2008/03/pinwheel-galaxy-m101.html
http://tispaquin.blogspot.com/2008/03/ngc-1300-in-eridanus.html
And of course, the Baboon Nebula:
http://tispaquin.blogspot.com/2008/03/baboon-nebula.html
April 7th, 2009 at 6:08 am
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