A little over 2000 light years away, toward the constellation of Cepheus, is a place where stars are being born. It’s a nebula, a gas cloud, and it’s called IC 1396. It’s monstrous, well over a hundred light years across – even at its tremendous distance, it’s wider than six full Moons in our sky.
Finnish astrophotographer J-P Metsävainio observed IC 1396, making a gorgeous image of it. But he wasn’t satisfied just doing that. He’d been playing with making 3D images for some time, and decided this might be a good opportunity to make a model of the structure of the nebula, and then create an animated GIF of it.
The results are… well, see for yourself:
Holy. Haleakala! [The filesize is 7Mb, so it may take a while to load.]
OK, let me be clear: this is not actually showing you the 3D structure of the nebula. It’s an approximation, a guess based on various assumptions on how nebulae are shaped. J-P broke the image up into layers, made a surface model of it, then remapped it all into different frames seen from different angles. He then put those together to make the animated GIF you see here.
The structure may not be completely real, but it’s still awesome… and it gives you a sense of the shape and composition of the gas cloud. The star in the center is the ionizing source; that is, it’s a hot, young, massive star blasting out ultraviolet light, and that’s what’s making the nebula glow. The dark ribbons are filaments of dust which absorb optical light (the kind of light we see). Many of them seem to point toward the central star. That’s because at their head is a dense clump of matter, and that’s getting eaten away by the light and fierce winds from that hot star. Material from the clump gets blown back and away from the star, like sandbars in a stream. It’s a very common structure in nebulae like this.
One thing that is pretty accurate is how the gas in the interior is blue, and red on the outside. Read More
We live in the outskirts of our disk-shaped galaxy, our Sun and planets located about halfway from the center to the edge. This is a bit like living a few kilometers away from a city, in the suburbs. From that distance, when you look toward the city, you see more buildings, more activity, just more stuff going on.
The same thing is true for us on Earth: the center of the galaxy (downtown) is located toward the constellations of Sagittarius and Scorpius, so when we look in that direction there’s lots of fun things to see: more stars, more gas and dust, more clusters, more stellar nurseries.
And when you point the monster Very Large Telescopes ginormous 8 meter mirror in that direction you can see amazing details in that buzzing hubbub, like this lovely shot of the nebula NGC 6357:
[Click to ennebulanate, or grab the 3760 x 1560 pixel version. note: I rotated the image to make it fit the blog better and so you can see it more properly embiggened here.]
This piece is actually part of a much larger complex of gas and dust, but shows some nice features. The whole place is lousy with hydrogen gas, glowing rosy red due to energy pumped into it from young, massive, hot stars. Those stars are forming from that very gas, so they’re lighting up their own nursery. Running right through the middle is a river of interstellar dust – not like the dust bunnies under your bed, this is actually more like soot, and made up of complex clumps of organic molecules. This dust absorbs and blocks light behind it, so it looks like it’s splitting the gas cloud in half.
You can also see some structures in the dust, like the "fingers" of material at the top pointing to the center of the gas. Those are actually dense clumps of material being slowly blasted away by the fierce, intense ultraviolet light from newborn stars. Think of them like sandbars in a river getting eaten away by the current. They point right at the stars doing the deed, a cosmic "j’accuse!"
Nebulae like this are among my favorite objects in the sky. They’re beautiful, they’re fascinating, and it’s more than a little mind-blowing to know that there are dozens, hundreds, maybe thousands of stars being born in these objects even as we watch. And it also gives me a bit of a shiver to know that these objects are ephemeral, too: the stars being born really are slowly eating away at the material… and many of these stars will explode as supernovae someday, and that destruction won’t be slow anymore! The onslaught of high-energy radiation and material moving outwards from those stellar blasts at thousands of kilometers per second will make short work of this nebula. So take a look while you can. In a million years or four, this whole thing will be gone.
The sky is not as it seems.
Certainly, gazing upon it on a clear night you see so much: stars, planets, the glow of hot gas here and there… but there’s also darkness. Look at the Milky Way, its stream split down the middle by a rift of black. Gape at a gaudy nebula, and you’ll see it pocked here and there by pools of black.
But what is inky pitch to our eyes glows with a cold light to those attuned to it.
Tell me, what do you see here?
The bright star is obvious enough, but you can also, dimly, see a feathered stripe of black splashed across the vista, blocking, absorbing the light from stars behind it. Details are muted, structure difficult to ascertain, and you strain to see features that your brain cannot interpret.
But that’s with your eyes. Try again, look at it, but this time, widen your view. See it now?
Well done! Where before you saw material absorbing light, now it emits! Of course, unbeknownst to you, you had some help: the ESO APEX telescope in Chile. It sees into the far, far infrared, where light is so stretched out it is entirely invisible to humans. In fact, the wavelength of light is so wide there that if it were a vibrating string, you could physically see the crests and troughs, since each would be separated by the next by nearly a millimeter. The light your eye can see has a wavelength only a thousandth that wide.
When APEX looked at this ribbon of dark, frigidly cold dust, it sees the material glowing. What we see as dark, it sees as bright. You can even compare the two directly, using a slider over the two versions of this picture, unveiling precisely what your now-expanded vision can take in.
Cold dust is the bane of the astronomer who uses merely visible light, since it blocks the view behind it. But one person’s poison is another’s meat, and if you study the material that wends its way between the stars — and sometimes comes together to form them — then the view from APEX is sustenance for you. This material is barely above the ultimate freezing point of absolute zero, and you might think it dead and useless. But from such stuff are you and I descended, and everything you see around you.
So when you do peer around you, and take in your environment, your surroundings, your home, look again. You are surrounded by the invisible, permeated by it… but always remember, it was invisible only until we chose to look for it. We created the means necessary to do so, and when we did the Universe opened up before us.
Image credit: ESO/APEX (MPIfR/ESO/OSO)/A. Hacar et al./Digitized Sky Survey 2. Acknowledgment: Davide De Martin.
Something like 6000 light years away, roughly toward the downtown area of our galaxy, lies NGC 6604, a tight cluster of young, massive, hot, bright stars. Just starting to shrug off the gas cloud of its birth, these stars emit a fierce light that makes the gas glow. When you point the 2.2 meter ESO/MPG telescope at this cluster what you get is startling beauty:
[Click to ennebulenate, or grab the cosmic 8600 x 8400 pixel version.]
NGC 6604 is the compact group of bright blue stars in the upper left. This whole complex of gas (called Sharpless 2-54) is about 200 – 250 light years across, making it rather huge! You’re only seeing a fraction of it here, though. It’s actually part of an even larger series of nebulae which include the more famous Eagle nebula (the Pillars of Creation) and the Omega nebula.
The image is a composite of pictures from different filters. Ultraviolet and blue filtered images were combined to make blue in this image; green filtered light is colored green, yellowish light from nitrogen is yellow, and the red is actually red from warm hydrogen. As you can see, hydrogen is plentiful in this area!
Also, see those odd diagonal features on the lower left? Those extend for a long way, well outside the frame here. That structure is called a "chimney", and may be 650 light years long! As stars are born, they can blow massive winds from their surfaces. This puts pressure on the surround gas, and if there’s a weak spot — where the gas is less dense, or if it’s near the edge of the cloud — the winds can push through. It’s not clear exactly how these form, or why they tend to be so straight. It’s suspected magnetic fields are involved, but that complicates things hugely. Still, the chimney in Sharpless 2-54 is the closest one known (of dozens), providing a nice clear view of it. If we ever do figure out the detail mechanics of chimneys, no doubt this one will play a role.
Image credit: ESO
- Desktop Project Part 26: Carina will keelhaul your brain
- The gorgeous birth pangs of young stars
- Kali ma… Kali ma… Kali ma, shakti deh!
- The new VLT Survey Telescope delivers spectacular images
April 24th marks the 22nd anniversary of Hubble’s launch into space. To celebrate it, NASA and ESA released this devastating panoramic view (also available here) of the mighty star-forming region 30 Doradus:
Yegads. [Click to embiggen, or get the 4000 x 3200 pixel version, or grab the ginormous 267 Mb 20,323 x 16,259 pixel version. There's also a way cool zoomable image too.]
30 Dor is a vast, sprawling, and chaotic region located in the Large Magellanic Cloud, a dwarf irregular galaxy that orbits our Milky Way. Even though it’s about 170,000 light years away it’s so bright it’s easily visible using binoculars (if you happen to live in the southern hemisphere or not far from the equator). The reason it’s so bright is that this stellar nursery is churning out thousands of stars, and some of them are the massive, hot, and blue type. These flood the surrounding gas with ultraviolet light which makes the gas glow.
In fact, those young stars are so luminous and energetic they’re eating away the cloud from the inside out! Those big cavities you see are where the light and fierce winds of subatomic particles blown from the stars are slamming onto the gas, pushing it outwards. The edges of the cavities are bright because that’s where gas piles up, and shines more brightly.
In fact, the folks at Chandra released a similar version of this image, except they added observations from that observatory, which detects X-rays (as well as an image using Spitzer which sees in infrared). X-rays are emitted from extremely hot gas, and as you can see in the image inset here (click to embiggen) the cavities are filled with X-ray emitting material (colored blue in the image). I wrote more about this in a post when a similar image was released.
One of the basic principles of modern science is that the physics we understand here, on Earth, work everywhere. This turns out to be a pretty good assumption, because we see it coming true time and again. That knowledge can then be used to figure out things that are happening at very large distances — even well across the Universe.
With that in mind, I present to you LAB-1: a glowing glob of gas as seen by the European Southern Observatory’s Very Large Telescope:
[Click to, um, englobenate.]
This, however, is no ordinary Space Blob: it’s located at the staggering distance of 11.5 billion light years from Earth! Not very many objects have been seen farther away than this, and it’s one of the single biggest discrete structures seen this far away. It’s about 300,000 light years across — three quintillion kilometers, or three times the diameter of our own galaxy. That’s pretty flipping big.
And although it’s faint to our telescopes, at that distance it must actually be tremendously luminous for us to see it at all. Something is making it glow fiercely, but what? One hint is in the cloud’s name: the LAB in LAB-1 stands for Lyman Alpha Blob. Lyman Alpha (written as Lyman-α) is a specific color of light you get from hot hydrogen gas (just so’s you know, it’s emitted when the electron in a hydrogen atom jumps down from the second to the lowest orbital energy state). Normally, Lyman-α is in the ultraviolet, but this blob is so far away the light is shifted by the expanding Universe into the optical region — that’s why it looks green in the image above.
It takes a goodly amount of energy to create Lyman-α light, so something big is going on here. Maybe this gas cloud is collapsing under its own gravity, and is heated up. Or maybe there are big galaxies inside of it, causing it to glow. How can we tell which is the culprit?
It turns out there is a way: polarization.
[Update: I originally had called this the Very Large Survey Telescope, but have learned it's actually the VLT (for Very Large Telescope) Survey Telescope. I've corrected this in the title and below. I like my less-redundant name for it better, but it's best to be accurate.]
The European Southern Observatory is an agency that governs some of the best telescopes on the planet, and they just added a new eye on the sky: the VLTe Survey Telescope (VST), a 2.6 meter ‘scope in Chile. There are lots of telescopes of similar size dotting our planet, but what makes this one special is its huge field of view — a solid one degree across, twice the diameter of the Moon on the sky – and the resolution of the camera: a terrifying 268 megapixels!
When you put that together, you get some dazzling pictures, like this one of the globular cluster Omega Centauri:
[Click to englobulenate to a 4000 x 4000 pixel 13 MB image, or grab yourself the internet-choking 14,540 x 14,540 pixel 280 MB version.]
Omega Cen is one of the largest globular clusters of the 150 or so orbiting the Milky Way galaxy, a collection of hundreds of thousands or even millions of stars all orbiting the cluster center willy-nilly like bees swarming around a hive. Telescopes like the VST will allow astronomers to survey these clusters quickly and deeply, which is important because it’s sometimes difficult to know what stars are in the cluster and which happen to be in the background or foreground. You have to get a good census of cluster membership before moving on to studying how old the stars are, what they’re made of, and how they behave. Since globulars are among the oldest objects in the Universe and are tied with galaxy formation, understanding them leads to understanding a great deal more.
VST also took this spectacular picture of the star-forming region M17, also known as the Omega nebula:
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