Hey, it’s been way too long since I’ve done a Spiral Galaxy Monday, so here’s a good one. My love for big splashy spiral galaxies is well documented, but sometimes I also love one when it gets a bit edgy.
Which is why I present to you NGC 4183, a very nearly edge-on spiral in the constellation of Canes Venatici, the hunting dogs:
[Click to galactinate.]
This Hubble image is pretty amazing: you can see individual stars in the galaxy, even though it’s 55 million light years away! That’s 550 quintillion kilometers, in case you’re wondering.
And astronomers consider that to be close by as galaxies go.
This unusual image is a combination of visible light from the galaxy plus light in the near-infrared, just outside what the human eye can detect. You can see bluer regions where stars are busy being born, the more massive and hotter newborns lighting up their surrounding gas. You can also see long clouds of dust – complex chains of organic molecules – which are opaque to visible light, so they block the starlight behind them.
This galaxy is somewhat similar to our own. It’s a bit smaller, 80,000 or so light years across, but like ours it’s an open spiral (which, even though it’s edge-on, can be determined in a number of ways, including radio observations which trace the arms of the galaxy). The observations making up the image were taken as part of a project using Hubble to characterize nearby edge-on spirals, and the image itself was put together by Luca Limatola as part of the Hubble’s Hidden Treasures project – encouraging people to find overlooked Hubble observations and create beautiful images from them.
I’d say this counts.
ESA/Hubble & NASA. Acknowledgement: Luca Limatola
Lying roughly 50 million light years from Earth is the magnificent spiral galaxy NGC 5033. Although that distance is a soul-crushing 500 quintillion kilometers, it’s actually relatively close by on the cosmic scale. Close enough that a lot of detail can be seen in the galaxy… and it also makes for a stunner of a picture:
[Click to darmokenate.]
This shot was taken by friend-of-the-BA-blog Adam Block using the 0.8 meter Schulman Telescope on Mount Lemmon in Arizona. It’s a whopping 13 hour exposure taken in near-true color.
It’s amazing what you can see in just this picture if you know what to look for. The spiral arms of the galaxy are fairly open, which is common enough, but the outer ones stick out a bit more than you might expect. The nucleus is very small and bright, more so than I’d expect for a typical spiral as well. Both of those things led me to expect this is an active galaxy, and that turns out to be the case.
Every big galaxy – ours included – has a supermassive black hole in the center. The Milky Way’s is 4 million times the mass of our Sun! In some galaxies, like ours, happily, the black hole is just sitting there. But in some there is gas actively falling into the hole. It spirals around and forms a very hot and very large disk, which glows fiercely as the matter is heated to temperatures of millions of degrees. They disk can blast out light from radio waves up to X-rays, and we say that the galaxy is "active".
A quick search of the literature didn’t turn up any measurements for the mass of black hole in NGC 5033, but it does confirm that it’s an active galaxy. Interestingly, the black hole is not located in the exact center of the galaxy! That’s very unusual, and indicates that NGC 5033 recently merged with another galaxy, probably a smaller one. It’s a cannibal! But then, most big galaxies are. It’s how they get big… and you’re living inside a big one, so there you go.
This may explain the wide arms on the galaxy as well; a collision and merger can distort the shape of the galaxy. Also, check out all the pink blobs along the arms: those are sites of furious star formation, the hot energetic massive young stars lighting up the gas around them. That also is common after a big collision.
Finally, one more nifty thing. You can see long ribbons of dark dust festooning the galaxy in the inner region. Dust absorbs light from stars behind it. But see how the dust looks like it’s only on one side of the galaxy, the half in the picture below the center? That’s an illusion, sortof. In reality there’s dust orbiting all around the center. However, there are stars above and below the disk of the galaxy, and the ones between us and the far side fill in the darkness a little bit, so the dust is less apparent. I’ve written about this before, and it does happen in quite a few spirals. Click the links in the Related Posts section below to see more gorgeous galaxies with this feature.
It’s funny how much information you can squeeze from a single picture! You have to be careful and not over-interpret it, and of course a lot of the things I’ve written here wouldn’t have been known without other observations of NGC 5033 using different telescopes and different methods in different types of light.
But even just one picture can tell you a lot. And in my opinion – and I tend to be right about these kinds of things – the wave of beauty that flows over you when looking at this picture is only enhanced by knowing more about the galaxy itself… and is boosted in no small way by the fact that we can know these things.
Image credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona
Messier 106 is an elongated spiral galaxy, seen by us at a low angle, in the constellation of Canes Venatici (CANE-eez ven-AT-ih-sigh, the hunting dogs). It’s about 25 million light years away, give or take. That may sound far — 250 million trillion kilometers! — but for Hubble, that’s considered close. So if you take a stack of Hubble images of M106 and put them together, as amateur astronomer Andre vd Hoeven did, you get a lovely picture it!
[Click to galactinate and get access to a zoomable version -- and you want to. I shrank the image considerably to get it to fit here. (UPDATE: there's a HUGE version at Flickr.)]
M106 looks a bit odd to my eye. The overall structure is pretty typical for a two-armed spiral seen at this low angle, but still… those red spots mark the location of busy star formation. The hot young stars heat up their surrounding gas, and the hydrogen in them reacts by glowing. Usually you see star formation that intense over a large region of the galaxy, or a small region, but not somewhere in between like this.
Not being familiar with the galaxy, I looked it up, and found the image inset here (which I’ve rotated to better match the Hubble image above). Right away we see something really weird: there are two more arms invisible in the Hubble shot!
What the what?
The inset picture is a combination from a lot of telescopes and wavelengths: visible light (displayed as gold), infrared (red), radio (purple) and X-ray (blue). The visible and IR line up well with Hubble’s view, but the radio and X-ray clearly show those extra arms. X-rays are emitted by very hot gas — like, million degrees hot — and radio is emitted by gas with a strong magnetic field permeating it. That’s a hint about what’s going on. Another is that the core of the galaxy is very bright, glowing more fiercely than you’d expect from a normal galaxy.
[Over the past few weeks, I've collected a metric ton of cool pictures to post, but somehow have never gotten around to actually posting them. Sometimes I was too busy, sometimes too lazy, sometimes they just fell by the wayside... but I decided my computer's desktop was getting cluttered, and I'll never clean it up without some sort of incentive. I've therefore made a pact with myself to post one of the pictures with an abbreviated description every day until they're gone, thus cleaning up my desktop, showing you neat and/or beautiful pictures, and making me feel better about my work habits. Enjoy.]
IC 342 is a relatively close by face-on spiral galaxy. At 10 million light years distant, it should actually be easily visible in binoculars and would be renowned for its incredible beauty except for one small problem: we have to peer through the thick dust choking our own galaxy to see it. It’s like sitting in a smoky room and trying to see something out the window on the far side of it. Your view is obscured.
But infrared light passes through dust quite easily, so when you turn an IR telescope — like NASA’s Spitzer Space Telescope — toward IC 342, what you get is spidery magic!
[Click to embiggen.]
Holy wow! What you’re seeing is the dust in IC 342 glowing where stars are being born; giant gas clouds are star birth factories, and are shrouded in dust. The stars’ light warms the dust up and it glows. The vast complex of nebulae trace out the spiral arms, looking like a web knit by an astronomically-minded spider.
I’ve written about IC 342 twice before. Once was when the NOAO released a gorgeous image of it taken by my friend Travis Rector. Seriously, click that link. The image is spectacular.
The other time was last year when WISE, another infrared observatory, took a look at IC 342. The view is pretty similar, as you might expect — the parts of the infrared spectrum making up both images are nearly the same — but Spitzer’s mirror is twice the size of the one in WISE, so the resolution is somewhat better.
Still, the more the merrier! IC 342 is a dramatic example of a nearby face-on spiral, and there aren’t too many of those around. Even though our own Milky Way galaxy has photobombed it into relative obscurity, the prying eyes of science are pretty good at seeing through all that.
I just got back from a week of travel, and I’m facing down a hundred emails, tons of news, about a billion things to write about, and then more travel later this week.
So when I see the folks at Hubble have posted a picture of a weird, pretty spiral, I figure it makes my job easier. I can just post a cool picture! So here it is:
[Click to galactinate.]
But dagnappit, I can’t leave it at that. I never can.
This is NGC 4980, a spiral about 65 million light years away or so. Most spirals have well-defined arms, but this one is just… odd. The arms are indistinct, and also fairly asymmetric. If I had to guess I’d say it recently suffered a collision with another galaxy, but apparently there are no other galaxies near it! I was rather surprised to find that there isn’t much in the professional literature about it; it’s close and bright, and worthy of some study.
The arms of the galaxy are there, and appear blue from the combined light of billions of young, massive, hot stars. As with many spirals, there are older, redder stars in the center; those are in the arms as well, but outshone by the brighter blue stars. Usually, the cores of spiral galaxies long ago ceased making stars, so all the big blue ones have long-since exploded, leaving behind the cooler, redder stars.
Note that the very core of the galaxy is a pin-point source of light. I saw on some websites that NGC 4980 is an emission line galaxy — it emits light at very specific colors, like a neon sign — which is a clear indication that a supermassive black hole is gobbling down matter there in the galaxy’s heart. As matter swirls in, it forms hot, flat disk (too small to see here) that is incredibly bright. This lights up clouds of nearby gas, which respond by glowing at those narrow slices of color. There aren’t too many of these "active galaxies" near us on a cosmic scale, so again I’m rather surprised this hasn’t been studied more!
So there you go. A lovely spiral to start your week, and one that’s also a little bit on the odd side. Frankly, lovely and odd is how most of my weeks start, so I’m happy to share.
There is just something wonderful when Hubble points to nearby spiral galaxies. Sprawling and detailed, we get both great resolution on smaller features as well as a jaw-dropping overview of a grand spiral… like, say, NGC 1073:
Yeah, I know. [Click to galactinate -- I had to shrink it to fit here, and it lost a lot of the coolness when I did -- or grab the 3900 x 3000 pixel version.]
NGC 1073 is a decent-sized spiral galaxy about 60 million light years away. It’s actually part of a small, tight group of galaxies many of which are far more famous (like NGC 1068). But 1073 is important because of a simple property: it looks like us.
While it’s not a perfect match, NGC 1073 does bear an interesting resemblance to our Milky Way galaxy (UGC 12158 looks more like our galaxy, but is far bigger, for example). Both have large, rectangular bars going across their centers. Bars are a bit odd, since you’d expect the arms just to wind all the way down to the center. But the gravity of a galaxy isn’t like the gravity of a solar system, with a big heavy star sitting in the center. Galaxies have their mass spread out over a long distance, so what gas and dust clouds and stars feel in the way of gravity is different, and bars are a natural outcome of that. However, they’re still not perfectly understood. Bars may form when galaxies collide, and they might be an indication of a galaxy reaching middle age. Perhaps there are other factors as well.
Studying galaxies like NGC 1073 will help us understand how bars form, and why we have one too. Remember, we’re stuck inside our galaxy and can’t see it from the outside (that picture above is an illustration based on detailed observations). It really helps our understanding of the Milky Way to observe galaxies like ours.
An important thing too is that the two galaxies are different in some ways: NGC 1073 has more open arms, for example, compared to our more tightly wound arms. Those differences are telling us something as well. What is it that makes one galaxy hold its arms closer in, and another to fling them out? Why does this galaxy have two arms, and that one three? If you can look at two galaxies that are alike except in one way, it’s easier to isolate the cause. So studying NGC 1073 is a great way to study ourselves.
It always makes me think of Nietzsche, who wrote on the nature of man, "And when you gaze long into an abyss, the abyss also gazes into you."
But on the nature of the Universe, it changes: "And when you gaze long into an abyss, your gaze falls back on yourself."
If you were wondering what was going on with the bright new supernova in the spiral galaxy M101, it’s now getting very difficult to observe due to its proximity to the Sun in the sky. But happily my friend, the accomplished astronomer Travis Rector, got a shot of it using the Mayall 4-meter telescope at Kitt Peak National Observatory. I would venture to say it’s one of the prettiest ones I’ve seen so far:
[Click to Chandrasekharenate.]
This was taken on September 18th, and the supernova is the bright blue star above and to the right of the center of the picture (to the left of the fuzzy red nebula). Pictures like this are important in pinning down the exact location of the supernova in the galaxy, so that after it fades the potential prescursor star can be found (though in this case, we already have pretty decent Hubble images of the field). Also, of course, big telescopes with sensitive detectors can give very accurate brightness measurements, which are absolutely critical in understanding how these objects change with time. This particular flavor of supernova is key to our understanding the size and scale of the Universe itself, so the more data — and the more accurate the data — we have, the better.
Image credit: T.A. Rector (University of Alaska Anchorage), H. Schweiker & S. Pakzad NOAO/AURA/NSF
- AAS 15: Travisty of astronomy (links to many of Travis Rector’s must-see photos!)
- Supernova update: it’s peaking now!
- M101 supernova update
- AstroAlert: Type Ia supernova in M101!
- Dwarf merging makes for an explosive combo
- Hubble delivers again: M101
A couple of weeks ago, astronomers spotted a star exploding in the nearby face-on spiral M101. They quickly determined it was a Type Ia, the kind used to calibrate the cosmic distance scale, and therefore a star of exceeding importance: we don’t see them close by (well, if 20+ million light years is "close", which it is to astronomers) very often. This one promised to get bright enough to study extremely well, which will help us understand these "standard candles" better.
Astronomers at Oxford University got a great shot of the galaxy and exploding star this week using a telescope located in California:
[Click to galactenate.]
The supernova is labeled. It was found by the Palomar Transient Factory, a group of folks looking for nearby supernovae, and was given the temporary name PTF 11kly; the official designation is SN 2011fe, the 136th supernova seen so far in 2011 (they’re named alphabetically for a given year, so the first 26 are 2011a – z, the second 26 are 2011ba – bz, etc.). This image was taken using a 0.8 meter telescope at the Las Cumbres Observatory Global Telescope Network; that’s a relatively small ‘scope, which tells you this a pretty bright object!
In fact, it appears to be reaching its peak brightness right now, and should be visible in binoculars. If you have a good view of Ursa Major, currently in the northwest at sunset, finding it shouldn’t be too difficult. Any decent star chart will show it (here’s one on wikipedia, for example). It’s raining here in Boulder (figures) but I’m hoping to get a chance to see it with my binoculars soon. Supernovae usually brighten for a couple of weeks and then fade more slowly, so if you can’t see it tonight or tomorrow it’s not critical, but of course the sooner you look the better.
Image credit: BJ Fulton/LCOGT. Tip o’ the accreting white dwarf to Dan Vergano (you should follow him on Twitter for lots of sciencey updates).
Sometimes I think it’s a good idea to start off the week with a gorgeous spiral galaxy. So here’s a fantastic example of a flocculent (fluffy or patchy) spiral: NGC 3521 in the constellation of Leo, care of the Very Large Telescope:
[Click to enflocculenate.]
NGC 3521 is a mere 35 million light years away (350 quintillion kilometers, a comfy airplane ride of just 50 trillion years or so; ask for an extra bag of peanuts), which is outside our local area but still close as the Universe goes. It’s half the size of our Milky Way home, about 50,000 light years across. [Note that it has that same effect I mentioned in an earlier post where the dust on the side of the galaxy closer to us appears darker; the light from intervening stars in that galaxy appear to "fill in" the dust on the other side.]
A large fraction of spiral galaxies have these patchy, ill-defined arms, so nature is telling us something: these things are easy to make. Grand design spirals — ones like ours, with splashy well-defined spiral arms — appear to be due to some global effect creating the arms; stars near the galaxy’s center orbit more quickly than ones farther out, so spiral arms should get wound up relative quickly. The fact that so many grand design spirals are seen means that this differential rotation does not destroy the spiral pattern: something most be maintaining it (we think it’s a traffic jam-like effect).
Flocculent spirals, on the other hand (arm?) are more likely to have some sort of local effect in the disk creating the patchiness — if it were some galaxy-spanning effect then we’d see better defined arms! Perhaps regions of local star formation from dense clouds are being stretched and pulled apart by differential rotation, for example, or, rather more likely, combination of several factors working in concert.
But the contrast between the two types of spirals is striking. And the differences between spirals don’t stop there: there are barred spirals, ones with small nuclei, ones with big nuclei, arms that are wound tightly, others loosely… the variety in nature on how to make a colossal structure 500 quadrillion kilometers across containing hundreds of billions of stars is pretty amazing. And we have a long way to go to understanding why they’re different! The math and physics of the behavior of galaxies is fierce, to say the least. They may look fluffy, but the science underlying them is anything but.
Image credit: ESO/O. Maliy
In something I’m considering making a tradition here at BA Central, here is your Monday morning jaw-dropping spiral galaxy: NGC 634 as seen by Hubble:
[Click to galactinate.]
Isn’t that something? This galaxy is a gorgeous nearly edge-on spiral, about 120,000 light years across or so — slightly bigger than the Milky Way — and 220 million light years away. The press release (at the link above) for this spiral talks about a supernova that blew up in this galaxy back in 2008, and I was going to write about that, but then something else tickled my brain.
Look at the picture. The disk of the galaxy, like in most spirals, is ribboned with dark dust lanes, huge clouds of complex organic molecules expelled by stars being born and stars dying. It’s pretty common to see them, but what struck me is the asymmetry of the lanes: they are darker on the bottom than at the top. The overwhelming impression is that we’re looking down on the spiral, so the dust lanes are more obvious on the near side than the far side.
This cannot be a physical effect of having dust only on one side of the galaxy. If it were, then random chance would make it pretty unlikely to have it on the side tipped toward us. Plus, I realized that I’ve seen this before! Read More