Spiral galaxies are among the most beautiful objects in the sky, and one of the most beautiful of them is M101, also known as the Pinwheel Galaxy. It’s a reliable favorite among amateur astronomers because it’s big, bright, and located near the north pole of the sky, so it’s easy to find for a big part of the year.
I’ve seen it many times through a telescope, but not quite like the way NASA’s Wide-field Infrared Survey Explorer (WISE) saw it: glowing fiercely in colors our eyes cannot detect:
[Click to galactinate.]
This image shows the galaxy in the far-infrared. What you see here as blue is actually starlight; green is from long organic compounds called PAHs, and red is from glowing dust, warmed by nearby star formation. Look at the gigantic red clouds where stars are being born! Thousands of these have been catalogued in the Pinwheel.
It’s actually an immense galaxy, twice the diameter of the Milky Way and possessing as many as ten times the number of stars. Our galaxy is no lightweight, but the Pinwheel is a monster. I wrote about it when Hubble released a gorgeous and incredibly detailed image of it back in 2006. There’s also a spectacular Spitzer image of it as well, which is also in the infrared, though in a different part of the IR spectrum.
The WISE mission shut its eye earlier this year when it ran out of coolant to keep its detectors cold (warm objects emit lots of IR, so keeping things cold prevents the detectors themselves from glowing in the very light they’re designed to see), but it surveyed the entire sky, returning a whole lot of data. I imagine we’ll be seeing more pictures like this coming from the database, as well as lots of amazing discoveries as scientists pore over it. The mission itself may be done, but the information it gave us goes on.
Image credit: NASA/JPL-Caltech/UCLA
Need a little face-on spiral awesomeness for your Monday morning? Then try this magnificent image of the nearby face-on spiral galaxy M33, aka the Triangulum Galaxy:
[Click to islanduniversalize, or go here to get the cosmic 7900 x 8000 pixel version.]
That not enough for ya? Then try this: Here’s a zoomable and pannable version!
This image is from Davide de Martin, who takes images from professional observatories, reprocesses them, and puts them on his Sky Factory website. M33 is a bit of an odd beast: it’s the second-closest spiral galaxy to our own — at about 3 million years away, it’s just a bit farther away than the Andromeda Galaxy — but it’s fainter than you might expect in the sky. That’s because it’s dinky, less than half the size of our Milky Way, and face-on, which means that small amount of light gets spread out, dimming it.
I’ve never seen it naked eye (Andromeda is actually pretty easy to spot from a dark site) but I’ve observed it many times with binoculars and a small telescope. Davide had a bit of an advantage though: this picture is from observations using the 4-meter Mayall telescope at Kitt Peak, a fine instrument indeed. The picture uses mostly "natural" color, adding together blue, green, and red-filtered images.
Cosmic coincidences always make me smile. The sky is pretty big, so finding two totally unrelated objects close together doesn’t happen often. But it does happen, like in this delightful image of the spiral galaxy NGC 3244 and the star TYC 7713 527-1:
This reminds me of another cosmic photobomb involving a star and a galaxy, but in this one the contrast isn’t quite so severe. The two objects seen here are unrelated; TYC 7713 is in our galaxy, while NGC 3244 is something like 100 million light years away. Maddeningly, I can’t find the distance to the star, so I can’t give you an exact ratio (I know it’s reddish, and a magnitude of about 10.2, but that could mean it’s an orange/red dwarf 100 light years away or a red giant 10,000 light years distant). Still, it’s way way closer to us than the galaxy. A millionth the distance? Maybe.
The galaxy is pretty nice; a nearly perfectly face-on spiral. I noticed it’s a bit lopsided, with one arm poking out a bit. Those clumps along the arm are regions of active star formation, and the dust lanes are clear too. Not bad for a galaxy a mere 2 arcminutes across in size — compare that to the Moon, which is 15 times larger in the sky! In real size, it’s not terribly big as galaxies go: about 25,000 light years across, only a quarter of the size of our galaxy.
In the press release linked above, it says this image was taken "with the help of" Václav Klaus, President of the Czech Republic, who was visiting the Very Large Telescope at the time. I wonder what his involvement was — it’s fun to think of the country’s leader using a joystick to swoosh and zoom the ‘scope. Still, it’s very nice indeed to see a major Head of State paying attention to science. Especially when it’s astronomy, and involved such a lovely image.
My love affair with spiral galaxies is well documented here on this blog. Of course, I’m biased: I live in one.
But some of them demand a little more attention than others, like the oddly off-kilter NGC 2442, aka the Meat Hook Galaxy:
That gorgeous image (click to galactinate, or grab the ginormous 6756 x 5687 pixel version) is from the MPG/ESO 2.2 meter telescope in Chile, and it definitely shows why NGC 2442 is a weird one. The one arm at the bottom is long and stretched out, the top one is thicker and dotted with pink star-forming regions, and the nucleus is way off-center. What the heck happened to this galaxy?
Perhaps a close-up by Hubble will help:
[Note: this image is rotated 180° from the one above.] Again, we see lots of red gas clouds glowing, fired up by massive stars forming in them. Interestingly, to me this view of the galaxy looks like a single bird feather, with the individual vanes arcing down. Those vanes are actually streamers of gas and dust pulled out like taffy from the main arm. Given all this, it’s pretty clear that NGC 2442 suffered a very close pass or even a collision with another galaxy sometime in the relatively recent past.
But what galaxy? Read More
I write about spiral galaxies here, and when I do it’s usually because they’re unusual. They’re really big, or small, or violent, or forming lots of stars.
So how about one that’s entirely normal? But don’t let that fool you: it’s still gorgeous. Take a gander at NGC 2841, a perfectly normal spiral galaxy as seen by Hubble:
Breathtaking, isn’t it? Click it to galactinate, or grab the super-dooper 3400 x 3000 pixel high-res version.
NGC 2841 is about 45 million light years way. That kinda sorta close, but not too far, keeping with our theme of averageness. It’s not particularly extraordinary in any way — assuming that any time you see an object tens of thousands of light years across and possessing a hundred billion stars, you’re seeing something ordinary. This type of galaxy is called flocculent: with lots of short arms instead of a two or three long, grand, majestic ones.
It’s forming stars, but not many. Those blue patches are where stars are being born, and they seem small, well-behaved, and scattered evenly across the galaxy’s disk. Everything about this galaxy is, well, polite. It doesn’t have enormous star-birth factories, it isn’t colliding with another galaxy, it doesn’t have weirdly-shaped arms.
Hmph. I’m no genius, and I know there’s lots of astronomy-related things I don’t know that much about. But what surprises me is that there still are complete surprises for me… like a type of galaxy I’ve never heard of!
So here’s NGC 3621, as seen by the 2.2 meter MPG/ESO telescope in La Silla, Chile:
[Click to galactinate to the 3500 x 3100 pixel version.]
Pretty cool, right? This is a near true-color image, using three filters that come close to mimicking the eye’s blue, yellow-green, and red sensitivity, as well as a filter that selects the light from warm hydrogen gas (shown as pinkish-red). As usual, that last bit shows where stars are actively being born.
At 22 million light years away, NGC 3621 looks like your usual big spiral galaxy: flat disk, arms sweeping out majestically, central bulge… hey, hold on there a second. Where’s the central bulge?
Hot (and cold) on the heels of my posting the infrared view of the nearby spiral M33, the European Space Agency just published this incredible picture of our other spiral neighbor, M31, the Andromeda Galaxy!
[Click to galactinate.]
Oh my. This is a composite of two orbiting observatory images: the far infrared using Herschel (colored orange), and the X-ray emission using XMM-Newton (blue). There’s so much to see! That’s not surprising, since at 2.5 million light years away, Andromeda is the closest big galaxy to us, and presents itself with loads of detail.
First, shown here is Robert Gendler’s magnificent visible-light image of the galaxy. You can see it’s tilted almost edge-on to us, but you can see the central bulge of old stars, the spiral arms winding out, the dark lanes of dust. This image has roughly the same orientation and border as the big one above, so you can compare them.
The infrared observations trace the presence of cold dust, created when stars are born and when they die. And by cold, I mean cold: much of it is just a few degrees above absolute zero. That dust is opaque in visible light, as you can see in Gendler’s shot. But it glows in infrared! The X-rays, on the other hand, are from incredibly hot gas heated to millions of degrees by neutron stars, black holes, and newly-born massive stars; you can see several individual objects in the galaxy’s core. Read More
Astronomers using the Chandra X-Ray Observatory may have found evidence for a young black hole: it was born in a titanic explosion just 31 years ago.
Black holes form when massive stars explode. The core of the star collapses, and if it’s massive enough (more than about 3 times the mass of the Sun), the gravity of the core can crush it down into a black hole.
Enter Supernova 1979c, a star that exploded in the nearby galaxy M100. About 50 million light years away, M100 is a lovely face-on spiral galaxy in the constellation Coma Berenices. SN1979c was discovered in — duh — 1979, and has been heavily studied for years since it was so bright, making it easy to see.
SN1979c was an interesting event, even for something as mind-numbingly violent as a supernova. The star that exploded was right on the edge of being massive enough to create a black hole; the total mass of the star was about 20 times the mass of the Sun, with a core of just about 3 solar masses. The question is, was the star big enough to create a black hole, or would the core collapse to form an incredibly dense neutron star?
Chandra observations may have answered this question. Read More
Spiral galaxies are among the most magnificent objects in space. Grand and sprawling, they are icons of the night sky.
Like a snapshot of coins tossed in the air, we see them at all angles, from face-on disks to nearly edge-on lines. And sometimes we catch them so precisely to the side that what we see is hard to believe is real. But then we get pictures like this one from Hubble of the galaxy NGC 4452:
[Click to galactinate, and yes, you really want to.]
There are lots of edge-on galaxies in the sky, like NGC 253 and NGC 4710, but this one is extraordinary. The alignment is perfect, and the disk is incredibly thin. Our Milky Way is 100,000 light years across and 2500 or so light years thick (a ratio of 40:1), but NGC 4452 looks even thinner than that; measuring off the picture I get a width-to-thickness ratio of 100:1.
Other things are obvious, too, and honestly a bit weird. For one thing, the central bulge of the galaxy is very small; in most edge-on galaxies it pokes above and below the disk like in NGC 4565, shown here. In that picture you can also see lots of dark dust; that’s actually complex organic molecules that are very efficient at absorbing visible light. They’re created when stars are born and when they die, and dust clouds tend to huddle close to the center of the disk.
[Note added later: It occurs to me there might be dust in the galaxy despite what I say in the next paragraph. That's because dust doesn't show up in the infrared very well, and one of the filters used was IR (as I note in a following paragraph). Also, the kind of camera used isn't as sensitive in the blue as it is in the IR, so that might also suppress seeing any dust that might be there. So take the next paragraph with -- haha -- a grain of salt.]
But NGC 4452 appears denuded of dust! I’ve never seen a galaxy quite so clean. I think it would actually pass the white glove test. Read More
I love big, splashy spiral galaxies. They are such eye candy, and of course their breadth and scale are magnificent. Sweeping, curved arms of stars and gas a hundred thousand light years long…
One of my favorites is NGC 253, a nearly edge-on spiral that lies roughly 11 million light years away in the constellation of Sculptor. I’ve seen it many, many times, but I was honestly surprised when a new image was released by the European Southern Observatory. I’ve never seen it like this:
Wow! Click to galactinate.
As you can see, it’s tilted pretty severely to our line of sight. You can clearly see the spiral arms, and the dust lanes wrapping around the galactic center. I was amazed to see the dust appears to be thicker on the top half than on the bottom. I was even more amazed to clearly see the bar — the elongated rectangular region in the center of the galaxy! That’s almost completely undetectable in a visible light image of the galaxy: