Tag: PAHs

Desktop Project Part 2: Unicorn, rainbow… soot?

By Phil Plait | March 27, 2012 7:00 am

[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.]

Did you know there’s a unicorn in the sky? There is: the constellation Monoceros (literally, one-horn). Located near Orion, when we look in that direction we’re peering into the disk of our Milky Way galaxy, and that means seeing lots of gas and dust. And when you do that with a telescope like WISE that sees into the far-infared, what you get is, well, magic:

This is SH2-284, a star forming nebula. The image is false color, but each hue represents a different part of the infrared spectrum. Blue and teal is mostly coming from stars, while red and yellow is dust. Green comes from a very specific kind of material called a polycyclic aromatic hydrocarbons — long-chain carbon molecules which are essentially soot. PAHs are made in various ways, but are abundant where stars are being born, and that’s what we’re seeing here.

There’s a cluster of young stars in the center of this cloud, and they’re so hot they’re eating out the inside of the cloud, creating that cavity you can see. Like so many of these structures, the clock is ticking: many of those stars will explode, and when they do they’ll tear the cloud apart. So take a look while you can… this unicorn rainbow cloud only has a few million years left before it’s extinct.

Image Credit: NASA/JPL-Caltech/WISE Team

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CATEGORIZED UNDER: Astronomy, Pretty pictures

Rudolph the red-dusted Strömgren sphere

By Phil Plait | December 23, 2011 10:48 am

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!

Read More

CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures
MORE ABOUT: Barnard 3, dust, infrared, PAHs, WISE

The coldly warm glow of star birth

By Phil Plait | August 23, 2010 10:05 am

For centuries, scientists have wondered how stars were born. There were lots of ideas, but precious little evidence to back them up.

That’s changed recently. Oh baby, how that’s changed. Check out this gorgeous image of the star-forming compact gas cloud called GL490:


You have to click that to get the ginormous 6000 x 6000 pixel version! It’s stunning.

This image is a combination of pictures taken by the Spitzer Space Telescope and the 2 Micron All-Sky Survey, or 2MASS. Both telescopes scan the sky in the infrared, well outside what our eyes can see. In this false-color image, blue represents 2.2 microns (the reddest light our human eyes can detect is about 0.7 microns, so this is three times that wavelength), green is 3.6 microns, and red is 4.5 microns. At these long wavelengths, what you tend to see are objects that astronomers call "warm", but that’s compared to empty space. In non-geek terms, these objects are colder than 100 Kelvin: about -170°C, or -280°F!

The green glow is from PAHs, or polycyclic aromatic hydrocarbons. Again, in non-geek lingo: big molecules of stinky soot. Read More

CATEGORIZED UNDER: Astronomy, Pretty pictures

A WISE flower blooms in space

By Phil Plait | March 22, 2010 8:00 am

I loves me some astronomical nebulae! And the Wide-field Infrared Survey Explorer — WISE — can really deliver:


[Click to emblossom.]

This image shows AFGL 3193 — what looks like a rosebud — a small piece of a very complicated region of gas, dust, and stars in the constellation of Cepheus in the northern sky. This region has star formation, cold and hot dust, and even a supernova remnant (called NGC 7822). This particular part seen by WISE shows a cluster of young stars called Berkeley 59 — the stars colored blue to the right — surrounded by the gas and dust from which they formed. This cluster is less than a million years old, and the massive, hot stars are blasting out radiation that is eating away at the cocoon surrounding them.

In the false-color image from WISE, red shows the coolest dust, blue and cyan warmer material, and green reveals long-chain organic molecules called polycyclic aromatic hydrocarbons, or PAHs. You can see how the PAHs appear to form around the rim of the nebula as the material there is compressed and warmed by the ultraviolet light and solar winds from the young stars. The filaments are testament to the forces tossed around as the stars go through their violent birth process. One of the stars in the cluster is a massive O5 star with dozens of times the mass of the Sun, and blasting out radiation at a rate 100,000 times that of the Sun!

I’m not sure just how big an area this image covers, but it’s roughly a degree across, twice the width of the Moon on the sky. The cluster is located about 3000 light years away, which is good: a lot of those stars will soon (well, in a few million years) explode, and this distance is far enough away that we’ll see a spectacular light show, but won’t wind up hurting us. Phew!

WISE is designed to survey the sky in infrared, literally spinning around and scanning the entire celestial sphere. It doesn’t have a field of view per se; the data come down in a stream and the astronomers on the ground can put them together at any scale they want, a little bit like Google maps. So expect to see lots more images of objects like this one, and you can get the whole list at the WISE gallery.

Image credit: NASA/JPL-Caltech/WISE Team

CATEGORIZED UNDER: Astronomy, Pretty pictures

The first spectacular views of the sky from WISE

By Phil Plait | February 17, 2010 10:08 am

NASA’s fledgling Wide-field Infrared Survey Explorer (WISE) opened its eyes a few weeks ago, and astronomers have just released the first of a torrent of spectacular images from it.

Since its launch last December, WISE has been surveying the sky, taking data continuously as it spins on its axis and orbits the Earth. A few images have been released before, but these new ones are fully processed, scientifically-calibrated, and gorgeous.

I have to start with this one, because it’s just so pretty! Behold Comet C/2007 Q3, aka Siding Spring:


Holy dirty snowballs! That’s gorgeous, a classic comet. When this image was taken, on January 10, 2010, the comet was 340 million kilometers (200 million miles) from Earth. That’s a good ways off, so I’m impressed with the detail of this image! It’s actually a four-color image: blue is 3.6 microns (about 5 times the reddest wavelength the human eye can see, so well out into the infrared), green is 4.6, orange is 12, and red is 22 microns.

Since the temperature of an objects determines the kind of light it emits, we can estimate the temperature of the comet just by eyeballing this picture. It’s mostly orange, meaning the comet is pouring out light at 12 microns. A human being radiates infrared from about 7 to 14 microns, so this means the parts of the comet emitting IR (and therefore seen by WISE in this image) are around the same temperature as a person! Well, in physics terms; in human terms it’s pretty cold, about -40 Celsius. And it’ll get even colder now since it’s on its way out of the inner solar system, away from the Sun’s warmth. It’ll dim as it cools, too, returning back to invisibility once again.

WISE is expected to see quite a few comets, and in fact discovered its first just a few days ago. I wonder how many it’ll find, and if they’ll all be this pretty…?

Let’s take a step farther out for the next WISE image:


Recognize that galaxy? I wouldn’t blame you if you didn’t, but it’s Andromeda! That’s the nearest large spiral to our Milky Way. It’s roughly 2.9 million light years away (estimates vary) and can be seen by the naked eye from a dark site. This stunning photo really accentuates how amazing WISE is: the field of view is 5 degrees across, the width of ten full Moons. The Hubble camera I used to work with would barely cover a pixel in this image!

Remember, this image is all infrared. What looks blue here is actually cold stuff compared to what we’re used to: old red stars, for example. The colors are a little different than in the comet image, but red is still the coolest material: dust. These complex molecules are created when massive stars are born and when they die. Since massive stars don’t live long, they tend to die near where they were born, so you see the dust constrained to very narrow areas where star formation occurs. Less hefty stars (like the Sun) live long enough to drift away from their nursery over billions of years, so they fill the galaxy’s disk (in blue). That’s why the dust is so vivid and tightly defined in this image.

If you look closely, you can see the left side of the galaxy is a bit distorted. That’s called a warp, and is probably caused by a nearby pass of another galaxy, or one Andromeda actually absorbed. The fuzzy blob just below the main galaxy is a dwarf elliptical companion to Andromeda, orbiting it like the Moon orbits the Earth. It’s mostly composed of old stars that look red to our eye, so again it’s blue in this false color image.

OK, one more. I like this one a lot: NGC 3603, a star-forming region about 20,000 light years from Earth:

It may not look familiar, but if you’ve been reading my blog for more than a couple of weeks, you’ve seen it: I wrote about a Hubble image of this very nebula. Now, if you’re like me, you’ll click that link, look at the Hubble image, and then try to figure out where it fits in this WISE shot. Pbbbt. Don’t bother. The Hubble image is only a tiny portion of this vast vista, a blip right in the middle of the brightest part of the WISE image. The S in WISE is for "Survey", which means it takes pictures of ginormous swaths of sky, far more than Hubble can do. In fact, Hubble could take picture after picture for weeks and not get a view of the sky as large as WISE does in a few minutes (of course, the Hubble image would be a whole lot more detailed…).

In this image, as before, red is warm dust, and blue is hotter material like stars. The green is what gets me though: at 12 microns, that reveals PAHs, polycyclic aromatic hydrocarbons. These complex organic compounds form in cool conditions in nebulae, which are lousy with them. They’re everywhere where the temperature isn’t too high to disintegrate them. They can form even larger molecules, and some people think they may be important in creating the molecules necessary for life on Earth. That’s not to say those molecules form in nebulae like NGC 3603 and then somehow get here; they most likely form right here as well. The point is, they look like they’re pretty easy to make if conditions are right… on Earth as it is in the heavens.

And the sheer size and breadth of the nebula is simply stunning! I’m so used to narrow fields of view that I forget sometimes just how large these objects are. This nebula is dozens of light years across, forming thousands upon thousands of stars. It’s among the biggest such star factories in our galaxy, and is certainly easily visible from other galaxies as well. Even from 20,000 light years away — 1/5 of the way across our entire galaxy — it’s clearly a formidable object.

And that’s the strength of WISE. It can see large objects, investigate the bigger picture of the sky, and do it in the longest regions of the infrared spectrum, light that we simply cannot explore from the ground — our air absorbs it, and all the warm objects around us glow fiercely at those energies. It would be like trying to find a firefly against the Sun! So we must launch observatories into space to peer at the far infrared light from cosmic objects, and WISE will be our eyes to do just that.

And from these images it looks like it’ll do a fine job. I’m impressed with these images. I’ve seen a few early release observations in my time — I’ve made a few myself! — and these are excellent. The whole mission is only supposed to last a few months; there is coolant on board for the detectors that can only go so far. In that short time it has a whole sky to observe, and that’s a lot of space. But that also means there’s a lot to see: galaxies, asteroids, comets, nebulae… maybe even a gamma-ray burst or two. The next few months will be very exciting for infrared astronomy!

Related posts:
WISE uncovers its first near-Earth asteroid
First light for WISE
The terrible beauty of chaotic starbirth
Spitzer peeks under a cradle’s blanket

Images credit: NASA/JPL-Caltech/UCLA

CATEGORIZED UNDER: Astronomy, Pretty pictures

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