Like human babies, newborn stars tend to blast out gas from both ends. Unlike infant people, when stars do it it’s because of things like angular momentum, magnetic fields, and radiation pressure.
Also unlike human babies, when stars blast out gas it’s incredibly beautiful. Like in the case of HH110, seen here using the Hubble Space Telescope:
[Click to encollimate -- and you want to -- or grab the huger 4000 x 3000 pixel version.]
Breathtaking, isn’t it? Ironically, given the analogy above.
Massive newborn stars are hot, bright, spin rapidly, and have strong magnetic fields. As matter flows away from the star, all of these combine to form two tornado-like structures, vast and violent, erupting away from the star’s poles. These two focused beams (astronomers call them "jets") can scream away from the star at hundreds of kilometers per second. As a class, we call them Herbig-Haro objects, or HH objects for short.
HH110 is a bit of an oddball since it only appears to have one beam of material instead of two. It’s also wider than most HH jets, and appears more turbulent, with lots of twisty structures and knots of material in it. And now we think we know why: it’s a bit of a fraud. It’s not its own HH object, but part of another!
Less than a light year away is a fainter HH object, called HH270. One of the jets from HH270 is pointed right at HH110, which seems like a pretty big coincidence. And it probably isn’t: the thinking now is that this HH270 jet is slamming into a dense cloud of material and getting deflected, and it’s this material splattering away that’s forming HH110! I’ve labeled the image above — taken using the Subaru telescope — to make this more clear (from the CASA website; there are images showing more of that region of space and it’s lousy with HH objects).
This idea makes a lot of sense, and explains the weird structure in HH110. Dense clouds of material are common near newborn stars — after all, stars form from gas clouds! — and it’s not too surprising that at some point a jet will slam in to one. You can even see the cloud in question in the picture; it’s the area which is black. The material there is so thick it’s blocking the light from stars behind it, so we see it because of what’s not there.
That’s pretty amazing. A light-years-long stream of gas beaming away from a star happens to hit a gas cloud, deflects in another direction, and the resulting chaotic mess gets bright enough to actually steal the limelight from the original event!
Sometimes, even by accident, the Universe makes beauty, and we can stand back in awe of it. Even better — we can figure out why. Science! I love this stuff.
Image credits: NASA, ESA and the Hubble Heritage team (STScI/AURA); Subaru/Bo Reipurth
- Hubble celebrates 20 years in space with a jaw-dropper [MUST SEE image of an HH object!]
- The gorgeous birth pangs of young stars
- A warm anniversary for Spitzer
- Spitzer sees star spew spurious spouts
- C-beams off the shoulder of Orion
You know why astronomy is cool? Because of things like this:
Galaxy clusters are collections of galaxies held together by their own gravity. We see clusters all over the place, and they’re among the largest structures in the Universe. We can find them at large distances, which means we see them as they (and the Universe) were young — it takes light a long time to travel across the cosmos. Astronomers went looking to find extremely distant clusters of galaxies, and found one at a staggering distance: 12.7 billion light years away!
Here’s an image showing the central part of the cluster:
[Click to bigbangenate.]
Each of those circled red dots is a young galaxy, so distant that the light has been on its way here for more than 90% of the current age of the Universe! And they’re almost lost among all those other stars and galaxies in the image (though their intense red color helps… as to why they’re red, read on).
Finding this cluster was a magnificent achievement. The astronomers used the massive 8.2 meter Subaru telescope to look at large swaths of the sky. They looked at the colors of the galaxies they found (PDF); distant objects would be so far away their light is significantly redshifted by the expansion of the Universe itself (I explain how this works here and here).
Galaxies are distributed throughout space, so you expect to see them scattered across the sky as well as in redshift (distance). When looking at one part of the sky, however, they found an unusually high concentration of galaxies that were very red. Using a different camera on Subaru, they took spectra of those galaxies — breaking the light up into very fine divisions of colors, like a rainbow with hundreds of colors in it — to accurately measure the redshifts of those galaxies. Spectroscopy of objects that faint is no easy task, but Subaru is a big ‘scope, and collect a lot of light even from faint objects at the remote reaches of the Universe,
The astronomers confirmed that many of the galaxies in their sample were at the same redshift (z = 6 for those in the know — which is a mighty big redshift). The odds of these galaxies all being at the same distance happening by chance is extremely small: only about one in a billion! So it’s pretty clear these galaxies really are physically associated with each other.
That is, clustered together.
This makes the cluster the most distant ever found that has been confirmed spectroscopically — one other has been found that might be farther away, but it hasn’t been confirmed yet. At 12.7 billion light years away, that means we see this cluster as it was a mere one billion years after the Universe itself formed! That provides key information about conditions in the early Universe, which are critical to understanding how it formed and changed as it aged.
The cluster itself is vast — it’s something like 50 million light years across. The team of astronomers used various methods to determine its mass, and their best guess is that its total mass is several thousand times the mass of our entire Milky Way galaxy! The estimation methods they used are fairly fuzzy, so it’s not clear how accurate this number really is. Still, the cluster is clearly huge, and massive. If we could see it today, it would probably rank among the largest structures in the Universe.
That’s not terribly surprising, if you think about it: only the biggest monster clusters can be seen at such a mind-crushing distance. The smaller ones will be harder to detect, so we’re likely to find the biggest.
Still, holy cow. I have read and written about extremely distant objects many, many times over the years, and have no doubt: I get chills every single time I think about this stuff. It wasn’t that long ago when the entire human race couldn’t be bothered to look beyond the tip of its collective nose. Now we can look into the fires of the Universe’s birth, into that forge itself, and tease out the secrets of how we came to be.
That’s why astronomy is cool.
- An ultradeep image that’s *full* of galaxies!
- Most distant object ever seen… maybe
- Another record breaker: ultra-deep image reveals ultra-distant galaxy
- Record-breaking galaxy found at the edge of the Universe
[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.
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.
There are quite a few mysteries in astronomy; things we don’t understand. The vast majority of them are smallish in scope, things that can probably be solved with a little more work, more observations. These are more like questions than outright mysteries; things we just don’t have the answers to quite yet.
But then there are some that really are mysteries: unexpected oddities that, for now, defy explanation. One of these reared its head again recently, when observations by the ground-based Subaru and Keck observatories were combined with those from the space-based telescopes Hubble and Spitzer. It doesn’t look like much of a mystery — just a red smudge — but it pushes the boundaries of what we think the very Universe itself can do.
[Click to enbigbangenate.]
First, holy cow, what an image! Incredibly, nearly every single object in that picture is an entire galaxy, a vast collection of billions of stars. They’re also very distant; I doubt any of the bigger ones are closer than several billion light years away.
And lurking off to the side, where you’d hardly notice it, is that little red guy. Named GN-108036, it’s at the soul-crushing distance of 12.9 billion light years away. That means that the light we see here left that galaxy when the Universe was only a few hundred million years old.
As you might imagine, it may look faint, but at that distance it’s remarkable we can see it at all. But we do, because it’s amazingly luminous, perhaps the most intrinsically bright galaxy seen at that distance ever found. Of course, we don’t see too many galaxies farther away than this! And that’s part of the mystery.
The Sun is literally a middle-aged star; approaching the midpoint between its birth over 4 billion years ago and its eventual death about 6 billion years from now. But the Sun is one of hundreds of billions of stars in the Milky Way galaxy, and we see them at all different ages, from their spastic births to their (in some cases) hyperspastic deaths. In many cases the way a star dies is foretold by how its born, so the study of star birth is a rich and fascinating field.
It’s also surpassingly beautiful, since stars are formed from the swirling chaos of thick clouds of gas and dust, lit up by the various newborns embedded within. You’ll find no finer example of this than the large nebula called Sharpless 2-239, a sprawling stellar nursery about 500 light years away in the direction of Taurus, and you may find no finer picture of it than this one taken by astronomer Adam Block using the 0.8 meter telescope at the Mt. Lemmon SkyCenter in Arizona:
[Click to ennebulenate, and yes, you want to.]
Isn’t that breathtaking? This image shows a portion of a much larger complex which currently has over a dozen stars forming inside it. Several of the stars you see here are quite young, only a few million years old. Since these are low mass stars like the Sun, and will merrily fuse hydrogen into helium for billions of years, this is like seeing a human baby when it’s less than a month old.
And, like babies will, these stars eject material from both ends: called bipolar outflow, twin beams of material (typically called "jets") are screaming out of these newborns at several hundred kilometers per second in opposite directions. These jets slam into the dense surrounding material, compressing it, heating it up, and causing it to glow. The structure you see fanning out to the lower left is from one of these jets, the one headed more or less toward us. The one moving in the other direction is mostly hidden from our view by the thick dust in the region.
But there’s much much more going on here…
Astronomers have found the most distant galaxy cluster ever seen: the sexily-named SXDF-XCLJ0218-0510.
First, the picture, then the words:
Yikes! What’s all that then?
Okay, first, this picture is littered with stars and galaxies. The galaxies are so far away they’re hard to distinguish from the stars! The dots that have arrows pointing to them are the galaxies that are most likely part of the cluster. The ones with circles have had their distance measured and are known to be part of the cluster for sure. The contour lines represent the detection of very hot gas, which is a dead giveaway that we’re dealing with a cluster here; all big clusters have gas swirling around them that gives off X-rays; the lines are like a topographic map telling you where the (otherwise invisible) gas is in the picture.
"So what?", you might say. We’ve seen lots of clusters before. Ah, but this one is different: it’s a whopping 9.6 billion light years away.
Billion. With a B.
Astronomers are like forensic investigators. We have all this data taken from the scene of some sort of event, and have to piece together what happened. But those folks on CSI have it easy: they get to actually walk around the scene, poke and prod it, examine various stains, and even take physical evidence back to the lab. Astronomers are stuck standing a quintillion kilometers away, and we only get to see things at one angle.
But oh, what an angle. If it pleases the court, I’d like to enter this evidence for your consideration:
That’s my kind of evidence (click to embiggen). It’s an image of the lovely grand-design spiral galaxy M81, one of the nearest major galaxies to our own. At about 12 million light years away it’s bright enough to be seen in binoculars (and in fact some extremely keen-eyed observers have been able to see it with their unaided eyes). That means it’s close enough to study in detail… and what detail!