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.
[The Desktop Project is my way of clearing all the pretty pictures off my computer's desktop, by posting one per day until they're gone. I think this week is it - I'm almost out!]
Dark matter is funny stuff. We’ve known about its existence for many decades, and the more we look the better our evidence gets. We know it has mass, and therefore gravity, but we don’t know what it is! We do, however, know what it isn’t: normal matter of any kind, like cold gas, rogue planets, black holes, dead stars, or anything else made of protons, neutrons and the other types of particles we deal with in everyday life.
Since careful observations have shown clearly it can’t be any kind of normal matter, it therefore must be some sort of exotic flavor of matter, some kind of particle we haven’t yet seen.
One thing we’re pretty sure about it, though, is that it doesn’t interact with normal matter except through gravity. Dark matter can pass right through you and you’d never know it. But put enough of it in one spot, and its gravity will reveal its presence.
Which is why the galaxy cluster Abell 520 is such a mystery. Here’s the beauty shot:
Pretty, isn’t it? Abell 520 is a galaxy cluster about 2.4 billion light years away, and a mass of several trillion times our Sun’s — it’s made of galaxies, each with billions of stars in them. And a galaxy cluster is a collection of hundreds or even thousands of galaxies bound together by their gravity. In fact, Abell 520 is more than one cluster: it’s actually a collision between two or more clusters! As they move through space, clusters can collide, and actually quite a few of these cosmic train wrecks are known.
When clusters collide, a lot of things happen. The gas clouds in between galaxies in the two cluster slams into each other, heating up to millions of degrees and glowing in X-rays. In the picture above, that gas has been colored green so you can see it (invisible to the eye, the X-rays were detected by the Chandra Observatory). The orange glow is from stars in galaxies (as seen by the Canada-France-Hawaii and Subaru telescopes). The blue is actually a map of the dark matter made using Hubble observations. The gravity of dark matter distorts the light passing through from more distant galaxies, making it possible to map out the location of the otherwise invisible stuff (you can read about how that’s done here and here).
Since dark matter doesn’t interact with normal matter, we expect it to simply pass through the collision point, sailing on as if nothing had happened. That’s been seen in a half dozen other galaxy cluster collisions, including the Bullet Cluster — hailed as definitive proof of the existence of dark matter — as well as Abell 2744 aka Pandora’s cluster (seen here on the right), and the newly found Musketball cluster.
But Abell 520 isn’t like those others. The problem is, there’s a clear peak in the dark matter right in the middle of the cluster, not off to the sides as you might expect. It looks as if the dark matter slammed to halt in the middle of the collision instead of sailing on.
Here’s the thing: this does not mean dark matter doesn’t exist, or we’re wrong about it. The other clusters I mentioned above make it clear we do have a pretty good grip — so to speak — on the behavior of dark matter.
[We're in the home stretch of my Desktop Project: going through all the pictures on my computer's desktop and posting one a day until they're gone. Only a few left now...]
This is the only one of my Desktop Project pictures that’s not actually a picture: it’s an illustration. It’s still pretty neat:
[Click to Schwarzschildenate.]
This drawing shows the binary star IGR J17091−3624, which is actually a normal star in the clutches of a black hole. They orbit each other, and the fierce gravity of the black hole is drawing material off the other star. This matter doesn’t fall straight into the black hole, however. Because the two stars orbit each other, the material coming off the normal star has some sideways velocity (technically, angular momentum) which causes it to spiral around the black hole and form a disk called the accretion disk.
This disk is hot. Very way incredibly yikes hot: probably something like 10 million degrees Celsius (27 million F). The heat comes from lots of forces including magnetism and plain old friction as particles rub against each other pretty violently before The Final Plunge.
Stuff that hot emits X-rays, and this binary is blasting them out. What’s so very interesting is that astronomers studying this black hole found that something was absorbing X-rays from the disk. Their best guess is that this is vaporized iron blasting away from the disk in a kind of black hole wind, and it’s hauling butt: the material is expanding at a speed upwards of 9300 km/sec — that’s 5800 miles per second, fast enough to cross the US in less than the tick of a watch. Want another unit? That means the wind is blowing at a brisk 0.03 times the speed of light!
I love black holes. They’re many things, but one they aren’t is subtle.
Another thing they are is ironic: although most people think of them as being able to suck down everything, including light, they power the most luminous objects in the Universe. This black hole probably is small, a few times the mass of the Sun. But much bigger ones exist, with millions or even billions of times the mass of the Sun. Those are in the centers of galaxies, and can have so much material falling into them and heating up that they can shine brighter than all the stars in the galaxy combined! It’s not the black hole itself that’s glowing, but it’s the center, the engine, behind that raw fury.
And that wind may be more than bright: there’s some evidence that the mighty gale from a galaxy’s central black hole affects the overall state of the galaxy itself. It may be tied to the way stars form in the galaxy, and even the size of the galaxy itself. Mind you, even a black hole with a billion times the Sun’s mass is still only as small fraction of a galaxy, which might have hundreds of billions of stars! So while you might think of something like that as a monster, it’s actually more amazing to me that something so tiny can be so influential on such a huge scale.
Illustration credit: NASA/CXC/M.Weiss
450 million light years away are two interacting galaxies. Both spirals, they are caught in each other’s gravitational claws. Already distorted and bound, eventually, to merge into one larger galaxy in a few million years, the view we have of them from Earth is both amazing and lovely… and hey: they’re punctuating their own predicament!
[Click to exclamatenate.]
Looking a lot like an exclamation point, the two galaxies together are called Arp 302 (or VV 340). This image is a combination of pictures from the Chandra X-Ray Observatory (purple) and Hubble (red, green, and blue). The bottom galaxy is a face-on spiral, while the upper one is seen more edge-on, giving the pair their typographical appearance.
The Carina nebula is a sprawling, monstrous complex of gas located a mere 7500 light years from Earth. Hundreds of light years across, it’s massive enough to create thousands of stars like the Sun. Tens of thousands.
And churn out stars it does. Embedded in the nebula are several clusters of newborn stars, and many of these stars are so massive they’re nearly at the limit of how big a star can be without tearing itself apart. Stars that big explode as supernovae, and a new mosaic by the orbiting Chandra X-ray Observatory indicate they’ve been popping off in the nebula for quite some time:
[Click to enchandrasekharlimitenate.]
This image is pretty amazing: it’s a mosaic of 22 separate images by Chandra, covering 1.4 square degrees (seven times the area of the full Moon on the sky), and represents an exposure time of 1.2 million seconds! Since it shows X-rays coming from astronomical objects, it’s false color: red is from lower energy X-rays, green is medium energy, and blue from the highest energy photons.
The diffuse glow is from two sources: the stellar winds from those massive stars slamming into surrounding ambient gas at high speed, and from the shock waves generated when supernovae explode. Both are extremely high-energy events, and produce copious amounts of X-rays. That long, horizontal arc is probably the edge of a bubble, a shell of gas piled up from the winds of stars and supernovae like snow piled up in front of a snowplow.
That’s evidence right there that Carina has been cranking out supernovae over the past few million years. Interestingly, it’s what’s missing that provides more proof. Read More
Astronomers have just announced something that took me by surprise: the dwarf irregular galaxy named Henize 2-10 has a fairly beefy supermassive black hole in it! Here’s a picture of the galaxy:
[Click to unendwarfenate.]
The image is a composite of images from Hubble (red, green, and blue), radio images from the Very Large Array in New Mexico (yellow), and X-rays from the Chandra Observatory (purple). The cross marks the location of the black hole.
Henize 2-10 is pretty dinky, only about 3000 light years across — the Milky Way is 100,000 for comparison. It’s about 30 million light years away, which is kinda sorta close by, at least close enough to get a decent look at it. Now, we know that big galaxies like ours have these monster black holes in their very centers; the Milky Way’s is about 4 million times the mass of the Sun. Many galaxies have much larger ones, like Andromeda which harbors one 35 times as massive as ours.
One of my favorite types of objects in space are the thin, ethereal shells of gas stars create when they die. So I was thrilled* to see this new image of one taken in exquisite detail by the Hubble Space Telescope:
[Click to supernovenate.]
I studied weird soap bubbles like this for quite some time for both my post-graduate degrees, and they still fascinate me. This one, called SNR 0509, is actually a very interesting example. There are lots of ring-shaped objects in the sky — the Helix nebula (seen below) may be the most canonical — but usually the ring itself is thick, the width of the band being a large fraction of the object diameter itself. Why does SNR 0509 have such a thin ring?
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
What happens when a star with a planetary system (or perhaps a close stellar companion) gets old, expands into a red giant, and engulfs its neighborhood?
"This", in this case, is the star BP Piscium (or just BP Psc), a star a bit less than twice the mass of the Sun located about 1000 light years away. The picture is actually a composite of both an optical image from the Lick Observatory (in white and green) and X-rays using the orbiting Chandra Observatory (purple).
The jets of matter streaming away are usually seen around young stars. When a star forms, there is a thick disk of material surrounding it. Due to processes not fully understood yet (though we know it has to do with the disk, the star’s spin, and the star’s magnetic field), matter and energy can be focused into those two beams, and they can blast away from the star’s poles at high velocity, stretching for several light years.
But there’s a monkey in the wrench here: BP Psc isn’t a young star.
Some 60 million light years from Earth is the monster galaxy M87. It’s a massive elliptical galaxy, one of the largest such in the nearby Universe… if you count 600 quintillion kilometers away as "nearby".
And when it comes to the Universe, I do.
It sits in the center of the Virgo cluster, a collection of roughly 1500 galaxies all bound to each other by gravity. At the heart of M87 is one of the biggest black holes ever seen: something like 6 billion times the mass of the Sun (the Milky Way has one as well, but it’s a paltry 4 million solar masses). It’s called a supermassive black hole, and it’s active. That means it’s a sloppy eater: as matter falls in to the hole, it piles up outside and forms a giant disk, which gets hot… millions of degrees hot. The tremendous heat and other titanic forces join up to blast away a huge amount of the otherwise incoming material. It’s not a nice, neat process, and when a black hole on that scale lets out a belch, it’s felt for hundreds of trillions of kilometers… as you can see in this image:
[Click to supermassivize.]
This is a composite of two images, one taken in radio wavelengths by the Very Large Array (in red) and the other in X-rays by the orbiting Chandra Observatory (in blue). The X-rays are being emitted by gas blasting away from the black hole, heated up by the disk and the magnetic fields affiliated with the hole itself. The radio waves are from gas that previously existed outside and farther away from the black hole, which is being slammed into, stirred up, and swept away by the outflowing gas.