[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)
[Over the next week or two, I'll be posting some of the many, many cool astronomical images I've been collecting and which are cluttering my computer's desktop. These are all really cool pictures, and I'm glad I'm finally getting around to writing about them!]
One of my favorite types of objects are things that look like other things. So how can I resist writing about the Pac-Man Nebula, aka NGC 281? As for why it’s called that, duh. The image inset here (click to powerpelletenate) was taken using a telescope that sees optical light, the kind our eyes see.
The resemblance is obvious, isn’t it? If you’re my age or younger, than Pac-Man is pretty much all you can see there (and it’s not the only cosmic object to look like that, either). Of course, as an astronomer, I also see hydrogen (red), oxygen (yellowish-green), dust (black; it absorbs optical light), and evidence of star formation. Those finger-like things on the left are formed when young stars blast out fierce amounts of ultraviolet light, and eat away at the gas surrounding them. Think of them like sandbars eroding under a current. Still, all-in-all: this is clearly Pac-Man, albeit one over 9000 light years away.
But what happens when you look with telescopes that see other kinds of light? Like, say, infrared and X-ray? Then things look really different. Opposite, even!
What do I mean by that? Well, let me show you:
See! On the left is a combination of infrared and X-ray observations taken with Spitzer and Chandra, and I scaled the images to show the same field of view. Stuff that’s dark in the optical picture on the right glows brightly in infrared on the left — mostly warm dust. And the pink glow is due to X-rays from the very young, massive, and hot stars in the center of the Pac-Man’s mouth (ghosts?).
Looking at nebulae like this at different wavelengths tells us different stories about them. We learn more about how stars form, and what happens to the nebula itself as they do. Eventually, the stars in the center will explode, becoming supernovae, and will tear the nebula apart. And you know what happens to the nebula then, right?
Image Credits: X-ray: NASA/CXC/CfA/S.Wolk; IR: NASA/JPL/CfA/S.Wolk; Optical: NSF/AURA/WIYN/Univ. of Alaska/T.A.Rector
[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.
What happens when you take a monster 4.1 meter telescope in the southern hemisphere and point it at the same patch of sky for 55 hours?
This. Oh my, this:
[Click to embiggen.]
OK, I know. At first glance it doesn’t look like much, does it? Just a field of stars. However, here’s the important bit: I had to take the somewhat larger original image and reduce it in size to fit my 610-pixel-wide blog. So how much bigger is the original?
It’s 17,000 x 11,000 pixels! If you happen to be sitting on a T1 line, then you can grab this massive 250 Mb file. And I surely suggest you do.
Because yeah, the brightest objects you see in this are stars. Probably a few hundred of them. But you have to look at the bigger image ! Why? Because what’s amazing, truly jaw-dropping and incredible is this:
There are over 200,000 galaxies filling this image!
Here’s a zoom of the image, centered on what looked to me to be one of the biggest galaxies in the frame, a nice edge-on spiral.
With the exception of a handful of blue-looking stars, everything in this zoom is a galaxy, probably billions of light years away. Those tiny red dots are galaxies so far away they crush our minds to dust: we’re seeing them with light that left them shortly after the Universe itself formed.
This light is ancient. And it came a long, long way.
By the way, that picture of the spiral there is not even at full resolution! Just to give you an idea, I cropped out just that galaxy in the full-res image and inset it here. If you want to find it in the full frame, it’s about one-third of the way in from the left, and one-third of the way down from the top. Happy hunting.
[Edited to add: I forgot to add that this galaxy is warped! See how the disk flares up on the left and down on the right, just a bit? This is very common in disk galaxies, and our own Milky Way does it too (see #9 at that link). It's usually caused when a nearby galaxy's gravity torques on the stars in the disk.]
These images were taken with VISTA, the European Southern Observatory’s Visible and Infrared Survey Telescope for Astronomy (VISTA), a 4.1 meter telescope in Chile. This huge image is actually composed of 6000 separate images, and is the single deepest infrared picture of the sky ever taken with this field of view. Hubble can get deeper, for example, but sees a much, much smaller part of the sky.
About 700 light years away sits the expanding death cry of a star: the Helix Nebula, a four-light-year wide gas cloud blasted out when a star that was once like the Sun gave up its life.
A new image of it in colors just outside what the human eye can see shows just how much it does look like a screaming star:
[Click to ennebulenate, or download the huge 6600 x 600 pixel 35 Mb version.]
This image is in the near-infrared, taken using the European Southern Observatory’s Visible and Infrared Survey Telescope for Astronomy (VISTA), a 4.1 meter telescope in Chile. Equipped with a whopping 67 megapixel camera it can take pictures of large areas of the sky. The Helix nebula fits that bill: it’s close enough to us that it’s nearly the size of the full Moon in the sky.
This image is pretty nifty. It accentuates cooler gas than what we see in visible light. What’s colored red in the picture is actually infrared light coming from molecular hydrogen, and shows the sharp ring-like edge of the nebula. What you’re seeing here is not so much a ring as it is the walls of a barrel-like structure, and we happen to be seeing it nearly right down the tube (see Related posts below for all the info you could want on this amazing object).
It also accentuates the long, long streamers pointing directly away from the center. Those are comet-like tails coming from denser clumps of material boiling away as the fierce ultraviolet light of the central star floods out, their material flowing radially outward. This is seen in other nebulae as well.
And while it’s beautiful and scientifically very useful (I would’ve killed for data this nice when I was researching these nebulae in grad school), it’s also something of an existential reminder: someday, our own Sun will look a bit like this. Probably not quite this bright and well-defined; our local star doesn’t quite have the power needed to light up its surroundings this way. But for all intent and purpose, you’re seeing a snapshot of our solar system in seven or eight billion years.
Just in case you needed a little perspective this morning.
Image credit: ESO/VISTA/J. Emerson. Acknowledgment: Cambridge Astronomical Survey Unit
I am fascinated by junk floating around stars. And no, not paparazzi, har har. I mean circumstellar material, literally gas and dust orbiting other stars. We see it around stars that are dying, we see it around stars being born, and we see it even after stars are well into their youth.
One such young’un is the bright and shiny HR4796, a star 240 light years away, with about twice the mass of the Sun. It’s known to be less than 10 million years old — compare that to the Sun’s age of 4.56 billion years; we’re 450 times older! — and has also been known for some time to have material around it in the shape of a ring. New observations by Japan’s huge 8.2 meter Subaru telescope have provided some of the sharpest views of this ring ever taken, and revealed some surprises.
Isn’t that lovely? [Click to enannulusenate.]
This picture is in the infrared, well outside what the human eye can see. The star itself is so bright it’s saturated, overexposed. That part of the picture is blocked out to make it easier to see details around it, but the star’s position is marked with a dot. The tendril-like structures radiating outward are not real, but are artifacts of the image processing techniques. You can ignore them.
The important thing is the ring itself, which is easy to spot. It’s almost certainly a circle, but we’re seeing it at an angle (about 13° from edge-on) so it looks like an ellipse. It’s huge; 22 billion km (14 billion miles) across, more than twice as wide as our entire solar system.
Again, the ring has been known for some time; for example it was seen in Hubble observations back in 2009 [NOTE: as astronomer (and my friend) Glenn Scheider points out in the comments below, HR 4706's ring was seen long before 2009. I wasn't clear when I wrote the previous statement; I was only alluding to one particular earlier observation, but it wound up sounding like it was the earliest such observation. My apologies for any confusion.]. But there is some new stuff here. For one, if you look along the long axis of the ring, you can see it looks fuzzy. That’s real! The ring is made of dust grains of various sizes, probably the result of bigger clumps colliding with each other and grinding themselves up into ever-smaller pieces (the authors of this reasearch (PDF) call this a "collisional cascade", my new favorite phrase for 2012). These grains of dust orbit the star, and the smaller ones get blown away from the star due to the pressure of its fierce light. Bigger grains are less affected, so they tend to stay in place.
So the main ring is made of bigger grains, while the smaller ones are blown back, forming a larger, extended ring. That fuzzier outer ring is fainter and harder to see, but we see it more easily along the long axis because of geometric effects (similar to why soap bubbles and giant shells of cosmic gas look like circles in space). So even though we only see a part of this outer ring, the fact that we only see it in those two spots is what makes it clear we’re seeing a ring at all! Funny how that works.
For some reason, a lot of gorgeous pictures are being released after I post my Top 24 Deep Space Pictures of 2011 gallery. Figures. Since I already had a few images from NASA’s WISE observatory in the gallery anyway I guess can’t complain too much, especially when they release one as pretty as this!
[Click to infraredenate.]
This is Barnard 3, a dusty, gassy region of the galaxy about a thousand light years away where young stars are lighting up their neighborhood. WISE observes the skies in the far infrared, well past what our eye can detect, so this false-color picture mostly picks out the dust warmed by nearby stars. What you see as green and yellow-green is actually from long, complex molecules similar to soot, called polycyclic aromatic hydrocarbons or PAHs. Red shows cooler material.
So what’s going on here? Right in the center of the red splotch is a star which is brighter and hotter than our Sun, and is flooding the surrounding material with ultraviolet light and a fast wind of subatomic particles (like the Sun’s solar wind, but a whole lot stronger and with a much, much farther reach). This has carved out a gigantic cavity in that stuff, creating a bubble about 25 light years in diameter — that’s huge: 250,000,000,000,000 kilometers across, more than 10,000 times the size of our solar system!
Astronomers may have, for the first time, directly imaged a planet still in the process of formation, gathering material from a debris disk surrounding its parent star.
First: Holy Haleakala!
Second: note the use of the word "may". It looks to me like it’s real, though.
Third: Oh, you want to see the picture? Well, let me do the honors:
The alleged planet, called LkCa 15b, is the blue spot in the image. The red shows material which is most likely accumulating onto the planet itself, building up its mass. The central star isn’t seen in this image because its light has been blocked out so the fainter material near it can be seen. The star’s position is marked by the star icon.
The image is in the infrared, taken using the monster Keck telescope in Hawaii. What’s shown in red is light at a wavelength of 3.7 microns (roughly five times what the human eye can see) and blue is from 2.1 microns, about three times what we can see. Warm material around the star is best seen at these wavelengths. If this is a planet, it’s at a temperature of about 500 – 1000 K (440° – 1340° F), and has a mass roughly six times that of Jupiter, or about 2000 times the Earth’s mass.
So is it a planet? Read More
I know I just posted a global color map of Saturn’s moon Titan, but sometimes it’s cool just to take a step back and look at a picture that gives a little context… and it doesn’t hurt that it’s a moody grayscale shot, too:
[Click to encronosenate.]
This shot of Titan was taken by the Cassini spacecraft back in August, and shows the moon superposed on Saturn’s rings, seen here almost — but not quite — edge-on.
The fact that you can see surface detail on Titan is a dead giveaway this shot was taken in the infrared: optical light, the kind we see, can’t penetrate the thick, hazy, nitrogen/methane atmosphere blanketing this moon. Infrared light gets through, though, so surface features can be seen. In fact, this image was taken using a filter that lets through light at 938 nanometers (the reddest light the human eye can see is about 750 nm). Methane is pretty good at absorbing light at a bunch of different wavelengths, but at 938 nm it’s transparent, so this is a particularly good place in the spectrum to look at Titan — astronomers call it the "methane window". Not only that, but this image also employed a polarizing filter, which blocks a lot of light from the atmospheric haze, making the surface easier to see (it also makes rainbows appear and disappear, too).
Not that the atmosphere is completely invisible in this picture: look around the moon’s edge and you can just see some of the upper atmospheric layers, and at the top you can easily spot the north polar hood, which may have water ice crystals in it.
And that dark region on Titan’s surface? It may have once been the bed of a methane sea, but now it’s a dry, vast area of wind-blown dunes, hydrocarbon grains collected by the Titanian winds. It’s called Shangri-La, and that makes me smile. I’m not sure anything at -180°C could be called a human paradise, but for astronomers, it’s certainly a scientific one.
We’ve sent space probes to every planet in our solar system (and if you’re a die-hard Pluto fan, you only have to wait 4 more years). And yet there is still much to see, much to explore. Not every world gives up its secrets easily, and perhaps none has been so difficult to probe than Titan, Saturn’s largest moon. Bigger than Mercury, second only to Jupiter’s Ganymede, Titan has an atmosphere of nitrogen so thick it has twice the Earth’s air pressure at its surface.
That thick, hazy atmosphere is impenetrable by optical light… but infrared light can pierce that veil, and the Cassini space probe is well-equipped with detectors that can see in that part of that spectrum. And after 7 years, and 78 fly-by passes of the huge moon, there are enough images for scientists to make this amazing global map:
Pretty awesome. And making this animation was a huge effort. First, not all of the passes were at the same distance, so scientists had to resize the images to match the scale. Cassini passed at different times of day for the local regions, so the sunlight angle changed, making illumination and shadowing different. The atmosphere of Titan is dynamic, changing with time, so again compensations must be made. It’s painstaking work, but the results are truly incredible: