[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. My Desktop Project -- posting one of those pictures every day -- is my way of clearing off my PC's desktop, and also showing you some truly amazing stuff. Enjoy!]
The Orion Nebula is a perennial favorite for astronomers. It’s big (the size of the full Moon on the sky), bright (visible to the naked eye), and gorgeous (even binoculars show some wispy details). It’s also scientifically fascinating, since it’s the closest example of a big star-forming factory in the Milky Way. We get a fantastic view of it and can study it in incredible detail (see Related Posts below for lots more pix).
Because of all that, it amazes me that anything can provide a truly new view of this old friend… but then our eyes don’t see into the deep infrared. When you combine images taken with the Herschel and Spitzer space telescopes, which probe the cosmos in that part of the spectrum, the portrait they make is just stunning:
[Click to ennebulenate.]
As lovely as this picture is, there’s an important science story going on here as well. The stars you see embedded in those filaments and knots of interstellar material are actually very, very young: probably only a few million years old, and on the verge of becoming full-fledged stars like the Sun. They’re still enshrouded in the dust and gas disks in which they formed. Near the embryonic stars, of course, the dust is warmer, and farther out it’s colder. Spitzer and Herschel see in different parts of the infrared, where the different temperatures of dust emit light, so they probe both the inner and outer parts of the clouds.
Astronomers used Herschel to observe this nebula in 2011, taking a series of images over time. What they found is that the stars and their dust changed in brightness by as much as 20% very rapidly — over weeks, when it would be expected to take years! It’s not clear what’s going on behind this variability. I suspect the disks of material around the stars are clumpy, and the inner region has clouds that block the starlight, shadowing the outer region. As that happens, the cooler part of the disk dims, which is what Herschel saw. Other processes may be at work as well, but any ideas as to what they are have to be tested against the observations.
Which is precisely why we observe even familiar objects with telescopes sensitive to different kinds of light. Ultraviolet, infrared, visible, radio, X-ray — these are all parts of the spectrum controlled by different processes, so by observing different flavors of light we see the different engines creating them. It’s the combination of these varying views that gives us insight (literally, in this case, since we’re seeing inside a nebula!) into the physical mechanisms of various astronomical phenomena.
Even though the Orion nebula is one of the best studied objects in the sky, there’s still a lot to learn from it. And as long as we keep our eyes open, especially across the electromagnetic spectrum, then more and more of its secrets will be revealed.
Image credit: ESA/NASA/JPL-Caltech/N. Billot (IRAM)
There’s cold water vapor orbiting the star TW Hydrae… and a lot of it. Enough to fill the Earth’s oceans thousands of times over!
TW Hydrae is a star located pretty close by, about 175 light years away. It’s lower mass than the Sun, so it glows an orange-red, but it’s also very young, less than 10 million years old. Stars that age are still shaking off the remnants of their formation, and that’s just the time you expect planets to get started.
And in fact it’s been known for years that TW Hydrae is surrounded by a giant disk, the leftover materials from its formation. Disks like that around other stars have been closely scrutinized, and we see lots of different materials in these disks, including various minerals, complex dust molecules, and even water. In general the water that’s been found is usually close in to the star and warm (which makes it easier to see).
Astronomers used the orbiting Herschel telescope to look at the disk of the star TW Hydrae in the infrared, and found water in the spectrum of the material there. And what they discovered is that it’s cold vapor, not warm. That’s the first time this has even been seen, and it’s kinda neat how this was done.
Like any scientist, I love a good mystery. Sometimes it’s fun when they are long, complicated, involve subtle and difficult layers, and require a vast effort to unravel.
And sometimes it’s cool when they are simply stated and simply solved. Like asking "Where does the water in Saturn’s upper atmosphere come from?" and finding out the answer is "It rains down from the moon Enceladus."
Water has been seen deep in Saturn’s atmosphere before, but a few years back it was detected in the upper atmosphere as well, and that’s a bit weird; there don’t appear to be any ways to get it from deep down in Saturn to the top parts of its clouds. So how did it get there?
Well, the tiny, icy moon Enceladus was discovered to have geysers at its south pole, actively spewing out quite a bit of water into space. Most of it goes into space and is gone forever. Some actually forms a ring around Saturn called the E-ring, and some no doubt hits other moons. Generally, when a moon blasts stuff into space (like Jupiter’s moon Io does with its sulfur volcanoes) the material forms a big donut-shaped region around the planet. It was figured that Enceladus was doing the same thing with water around Saturn, but even the Cassini spacecraft, which is right there, couldn’t detect it. It’s pretty hard to sample.
But astronomers used Herschel, an Earth-orbiting infrared observatory, to observe Saturn. They found a peculiar feature in the infrared spectrum of Saturn, and realized it’s from this Enceladusian water torus. Apparently, about 3-5% of the water from Enceladus’s geysers falls on Saturn, literally raining down in sufficient quantities to explain the presence of the water detected in the ringed planet’s upper atmosphere.
At the end of May, 2010, the European Space Agency’s orbiting Herschel telescope was pointed toward a dark cloud in space over 2500 light years away. What it saw may solve a bit of a scientific mystery… and is also truly beautiful:
[Click to ennebulanate.]
This object is called IC5146, and consists of the Cocoon nebula on the left, and two long streamers of gas extending to the right. Herschel is very sensitive to cold dust in the very far infrared; in this image blue shows gas and dust emitting at a wavelength of 70 microns (the reddest color the human eye can see is roughly 0.7 microns), green is 250 microns, and red 500 microns — that’s over 700 times the longest wavelength light the eye can detect.
The Cocoon nebula is a well-known gas cloud being lit up by a massive, hot star in its center. In the visible light image inset here — grab the stunning high-res version to compare to the Herschel shot — the dust is dark, since it absorbs the kind of light we see. Also, stars are pretty faint at these extreme infrared wavelengths, so they don’t interfere with the observations of the gas and dust. That’s why observatories like Herschel are so important: they allow us to investigate objects that might be invisible to other telescopes.
As you can see in the Herschel image, the entire region is interlaced with long, thin filaments of dust. This dust is cold: much of it is only about 15° Celsius above absolute zero, or -430°F! What’s so very interesting is that the filaments, no matter what length they are (and as seen in other parts of the sky by Herschel as well), seem to have about the same width of roughly 0.3 light years across. That argues very strongly that these filaments are formed from turbulence in the dust, probably caused by exploding stars roiling up the matter between stars. That width is just about what you’d expect as shock waves from exploding stars slam into each other, interact, and become turbulent.
But the Cassini Saturn probe sometimes sees things a little differently, and recently provided us with a sideways view of Mimas. Literally.
[Click to rickrollenate.]
On January 31, 2011, Cassini snapped this picture of the moon with the planet’s rings in the background. I really like this shot, since we see Mimas’s giant impact crater from the side. I don’t think I’ve ever seen it quite this way before.
A long time ago, Mimas got hit pretty hard with something pretty big. The apocalyptic impact carved a crater 130 km (80 miles) across in the moon, which we now call Herschel. In most pictures we see it from an angle and Mimas winds up looking an awful lot like the Death Star.
But in the big picture above the crater was almost edge-on, and you can see how seriously it messed up the moon: a pretty hefty portion of the edge of Mimas looks flat where the rim of the crater distorts the horizon. An impact this size anywhere on Earth would be, well, bad. Very very very bad. And it’s not like Mimas hasn’t suffered enough, as you can see it’s been hit thousands of times; the surface is saturated with craters.
But that’s the way it is in the solar system. A lot of debris is floating out there, and over billions of years physics cannot be denied. After all… you know the rules and so do I. If you’re a moon, those small objects are gonna run around and hurt you.
* That link is safe. Seriously. I promise. Go ahead, click it. I dare you.
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
A few years back, astronomers discovered that some distant galaxies were blasting out vast amounts of infrared light, but were very faint in visible light, the kind we see. They termed these objects ULIRGs ("you-lurgs"), for Ultra Luminous Infrared Galaxies. The idea is that these galaxies are forming lots of stars, but there was so much dust choking the region that all the visible light was blocked. However, infrared light can pierce through the dust, so telescopes that detect IR can see them. Due to the physics of the situation, astronomers also figured there must be two populations of these galaxies; the ones they had found, and another that was (very) slightly warmer.
I know, they don’t look like much, do they? But you have to realize what you’re seeing here: those circled blobs of light are entire galaxies, with billions of stars, and they’re a staggering 11 billion light years away.
That’s really, really far. The Universe is only 13.7 billion years old, so we’re seeing these galaxies as they were just a few billion years after the entire Universe came into being. Not only that, but the amount of infrared light these galaxies are emitting is truly terrifying: in the infrared alone, they are blasting out a solid trillion times the Sun’s entire energy output.
A trillion! 1,000,000,000,000! That’s a whole lot of energy. And it comes from a whole lot of newborn stars, because these galaxies are cranking out stars at a rate 700 times that of our own Milky Way galaxy! The view inside those galaxies must be breathtaking; imagine being surrounded by the Orion Nebula everywhere you look. Wow.
What cracks me up about this too, is how they found them. The European Space Agency is using the orbiting Herschel Infrared Observatory to take a survey of galaxies in the IR. It’s finding a lot of them; in the picture above every dot you see is an infrared source, most likely a galaxy. And that’s a small section of the sky; on the right is an image of a bigger part of the survey. You need to click it and see it full-res to get a sense of how many freaking galaxies there are out there!
As far as astronomical discoveries go, this is another in a long series of steps needed to understand the Universe. I know that in your daily life this may not affect you much; you have other things on your mind, daily stresses and such. But you know what? While I go about my everyday business, in my mind I’m occupied by all the mundane and gross worries of life just like you are, just like everyone else is. But somewhere back there, in some part of my brain, there is knowledge that sits there… and every now and again, it makes itself known.
We can see galaxies a hundred billion trillion kilometers away! We know that stars are being born there, stars like the Sun, and they’re being born every day! If you were there, the sky would be a riot of red and green gas strewn in sheets and ribbons and shock waves and festooned with brilliant jewel-like stars everywhere you looked!
Those wonders are out there, and they’re real. That makes my life better, just knowing that.
Image credit: ESA/SPIRE/HerMES
Cassini images of Saturn and its environs never get tiresome. And in fact, they can be downright jolting… like this stunning shot of the icy moon Mimas.
Cassini was 100,000 km (60,000 miles) from the small moon when it captured this moody image. It shows a view we can never get from Earth: a crescent Mimas, with the Sun well off to the side.
The giant crater is called Herschel, and it’s a whopping 130 km (80 miles) across. Whatever hit Mimas eons past was huge, and had it been any bigger, or moving any faster, the moon itself may have shattered. In fact, there’s some thinking that this happens to some smaller bodies in the solar system; they can get hit so hard they do shatter, and if the event isn’t too energetic the pieces can recoalesce, reintegrate. This may be why some asteroids are so low in density; they’re essentially rubble piles, like bags of glass.
Mimas was spared that fate those many, many years ago. What was left was an icy moon with a single brooding eye… reminding us that when we stare into the abyss, sometimes the abyss stares back.
Image credit: NASA/JPL/Space Science Institute