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.
Spiral galaxies are among the most beautiful objects in the sky, and one of the most beautiful of them is M101, also known as the Pinwheel Galaxy. It’s a reliable favorite among amateur astronomers because it’s big, bright, and located near the north pole of the sky, so it’s easy to find for a big part of the year.
I’ve seen it many times through a telescope, but not quite like the way NASA’s Wide-field Infrared Survey Explorer (WISE) saw it: glowing fiercely in colors our eyes cannot detect:
[Click to galactinate.]
This image shows the galaxy in the far-infrared. What you see here as blue is actually starlight; green is from long organic compounds called PAHs, and red is from glowing dust, warmed by nearby star formation. Look at the gigantic red clouds where stars are being born! Thousands of these have been catalogued in the Pinwheel.
It’s actually an immense galaxy, twice the diameter of the Milky Way and possessing as many as ten times the number of stars. Our galaxy is no lightweight, but the Pinwheel is a monster. I wrote about it when Hubble released a gorgeous and incredibly detailed image of it back in 2006. There’s also a spectacular Spitzer image of it as well, which is also in the infrared, though in a different part of the IR spectrum.
The WISE mission shut its eye earlier this year when it ran out of coolant to keep its detectors cold (warm objects emit lots of IR, so keeping things cold prevents the detectors themselves from glowing in the very light they’re designed to see), but it surveyed the entire sky, returning a whole lot of data. I imagine we’ll be seeing more pictures like this coming from the database, as well as lots of amazing discoveries as scientists pore over it. The mission itself may be done, but the information it gave us goes on.
Image credit: NASA/JPL-Caltech/UCLA
I love to post pretty pictures of galaxies and wax lyrical about their magnificent structure, complex history, and complicated internal compositions.
… and then there’s the Carina Dwarf galaxy. It’s so small and faint it wasn’t even discovered until 1977 even though it’s one of the closest galaxies in the sky! How did it avoid detection so long? This’ll make it obvious:
[Click to unendwarfenate.]
See it? Yeah, it’s that faint smattering of stars in the middle of the picture (the bright star near the center is in our Milky Way and coincidentally aligned with Carina). Not much to it, is there? It’s about 300,000 light years away, only 1/10th as far as the much brighter and more famous Andromeda Galaxy, and only about twice as distant as our two satellite galaxies, the Small and Large Magellanic Clouds, both of which are easily visible to the unaided eye.
Like the LMC and SMC, it is apparently a satellite of the Milky Way, but formed long after we did; studies of the stars in the Carina Dwarf indicate it’s only about 7 billion years old at most, while our galaxy is well over 10 billion years old. It probably formed from primordial gas orbiting the Milky Way, taking much longer due to its low mass and relatively quiet environment.
This image is a combination of observations taken with the 2.2 meter MPG/ESO and the Victor M. Blanco 4-meter telescopes in Chile. It shows that the galaxy has very little or no gas at all in it, and so its career in star-formation is long dead. But there’s still much to learn from such objects: they get eaten by bigger galaxies, for example. This cosmic cannibalism is one way galaxies like ours get so big, so studying these smaller bite-sized snacks in situ help us learn about ones we’ve already munched on.
Plus, galaxies like Carina might be the most common in the Universe! We just can’t see them because even at relatively small distances they fade away into the background. They may not be as flashy as spirals or as monstrous as giant elliptical galaxies, but they play an important role in building up such beasts. The more we know about them, the better we’ll understand the Universe itself.
Image credit: ESO/G. Bono & CTIO
- And the cottonball galaxies shall inherit the Universe
- Lonely galaxy is lonely. But it ate its friends.
- Alien clusters invade our galaxy!
- Obese, gluttonous, and cannibalistic is no way to go through life, son
I recently wrote about a mind-boggling event: astronomers capturing what are apparently the final moments in a star’s life as it was literally torn apart by a black hole.
Today, NASA has released some new pictures of the event, including this Hubble Space Telescope shot:
[Click to embiggen.]
I know, it may not look like much at first. But remember what you’re seeing: the violent death of a star ripped apart by the gravity of a black hole… and it’s happening 3.8 billion light years away! That’s about 40,000,000,000,000,000,000,000 kilometers, so the fact that we can see it at all is pretty amazing. And terrifying.
In this false-color Hubble image, the galaxy and explosion are marked. Pretty much everything you see in the picture is a distant galaxy, a billion of more light years away. Normally, the host galaxy itself would appear as a dot, at best with some small amount of fuzz around it, the glow of billions of stars reduced by the incredible distance. But the dying light of the star increased the galaxy’s brightness by a lot. A whole lot.
This image (click to greatly embiggen!) is a combination of visible light (white), ultraviolet (purple), and X-rays (yellow and red) from NASA’s Swift observatory, the satellite that first detected the explosion. While the spikes are not real — they’re just an optical effect from the telescope itself — it still speaks to the drama of what we’re seeing.
And so just what are we seeing?
Astronomers have just announced they have discovered what may be the most distant galaxy ever seen, smashing the previous record holder. This galaxy is at a mind-crushing distance of 13.2 billion light years from Earth, making it not just the most distant galaxy but also the most distant extant object ever detected!
Here is the object in question:
The small box shows the location of the galaxy, which is invisible by eye in the image. The zoomed region shows it in the infrared, where it glows more strongly.
[NOTE: Let me be clear up front and say that this is a candidate galaxy, since it hasn't been confirmed using other distance determination methods. However, having read the paper I think the astronomers did an excellent job showing this is very likely to be a galaxy 13.2 giga-light years away. From here on out I'll refer to it as if it's real, but to be fair bear in mind there is some small chance it may turn out not to be real.]
Named UDFj-39546284, the galaxy is seen as it was just 480 million years after the Universe itself formed! The previous record holder — which was announced just last October — was 13.1 billion light years away. This new galaxy beats that by 120 million light years, a substantial amount. Mind you, these galaxies formed not long after the Big Bang, which happened 13.73 billion years ago. We think the very first galaxies started forming 200 – 300 million years after the Bang; if that’s correct then we won’t see any galaxies more than about 13.5 billion light years away. Going from 13.1 to 13.2 billion light years represents a big jump closer to that ultimate limit!
The galaxy was found in the infrared Hubble Ultra Deep Field, or HUDF, an incredible observation where Hubble pointed at one patch of sky and stared at it for 173,000 seconds: 48 solid hours! After Hubble’s Wide Field Camera 3 observed it, this supposedly blank patch of sky came alive with thousands upon thousands of distant galaxies, and in fact the last record-breaking galaxy was found in the image. The picture here shows the whole HUDF image, with the first picture at the top of this post outlined. Click it to see it in full size, and you’ll start to get an appreciation of just how freaking tough these observations are. The sky is full of faint galaxies!
This new discovery was found using what’s called the dropout technique. Read More
The Universe is a big place.
I mean, really big. Big enough for anything. Literally, big enough for everything. Everything you see, everywhere you go, it’s all inside. And there’s room for all of it, with space to spare. I get used to it sometimes, and then, suddenly, I’m thrown into a state where I’m forced to remember just how much of the Universe there is.
Let me show you something:
[Click to galactinate, and while it may take a little while to download the entire 3500 x 2000 pixel image, it will definitely be worth your time.]
This is the nearby spiral galaxy NGC 1345 as seen by Hubble. Lovely, isn’t it? You wouldn’t even think it’s a spiral at first; the arms are so faint compared to the sprawling core and inner regions. But it so happens the galaxy is close to our own, making fainter parts easier to observe.
Now there you go. Did you see that? What I said? "The nearby spiral…". "The galaxy is close to our own…". But it isn’t.
Look. Let your eyes move to the top of the galaxy, just to the right of center. See that bright star? You can tell it’s a star because it has those spikes going through it, an artifact of how point sources are seen by some of the Hubble cameras. Given how bright it is, that star is almost certainly in our own galaxy, and not some luminous giant in NGC 1345; it’s just coincidentally superposed on the more distant galaxy. That means it’s no more than a few thousand light years away, and given its deep red color, that means it’s most likely a very cool and faint red dwarf, and therefore in all likelihood much closer even than that.
But even if it’s only a thousand light years away, that’s 10 quadrillion kilometers! That distance is impossible to imagine: it’s more than 60 million times farther away than the Sun… and the Sun is hardly close. If you could fly an airplane to the Sun, it would take 20 years. Twenty years! And that star is millions of times farther away.
… and that star is the closest thing in that picture. I said NGC 1345 is nearby, and on a cosmic scale it is; it’s part of a small cluster of galaxies a mere 85 million light years away: 850 quintillion kilometers. That’s 850,000,000,000,000,000,000 kilometers.
But now let your eyes roam over the image. You can see dozens of smaller galaxies crowding the frame. Those are background galaxies much, much farther away than NGC 1345. I’ve extracted three of them here. Each looks to be a spiral galaxy — the one on the upper right is edge-on, but the tell-tale dark dust lane across its middle is a dead giveaway that it’s a disk galaxy — and although the distances aren’t known, it’s safe to bet they are hundreds of millions of light years away. Maybe more. In my time on Hubble we’d routinely see background galaxies that were well over a billion light years away. Routinely. Mind you, each of these background objects is itself an entire galaxy, containing tens or hundreds of billion of stars, perhaps as big, rich, and diverse as our own Milky Way.
And in the course of things, this was a short exposure for Hubble, just a little over half an hour. I once worked on a Hubble image that had an exposure that lasted for days, and we saw objects so faint that the faintest star you can see with your naked eye would be ten billion times brighter. These objects were essentially as far away as anything we possibly can see.
And yet the Universe is deeper even than that. It stretches on and on… and while it’s finite — it has an actual size — in practical terms it’s infinite. Why? Because it’s expanding. If you could somehow hitch a ride on a photon, the fastest thing in the cosmos, you’d still never reach the edge of the Universe even if it had one. That’s because the edge would be receding away from you faster than you could reach it. You’d forever be playing catch-up. Literally, forever.
I sometimes think it’s fantastic that we can see anything at all when we gaze upwards. And yet, there it is. Splayed out for us to study, for us to explore.
Some people feel small, insignificant, when they look out into all that space, all that blackness. It’s easy to feel that way, but it’s not a fair assessment. It can be a struggle, and a mighty one, but it’s worth the effort to seek out the awe and the grandeur in it as well. In all that vastness, all that depth, it’s entirely possible there are trillions of planets like Earth, and maybe more. But none is this Earth. Nowhere else is there another you, another me.
In the end, when you make that effort, this is one of most important lessons you learn: we’re a part of all this. A unique part. And that’s a fine thing to know.
Image credit: ESA/Hubble & NASA
Spiral galaxies are among the most magnificent objects in space. Grand and sprawling, they are icons of the night sky.
Like a snapshot of coins tossed in the air, we see them at all angles, from face-on disks to nearly edge-on lines. And sometimes we catch them so precisely to the side that what we see is hard to believe is real. But then we get pictures like this one from Hubble of the galaxy NGC 4452:
[Click to galactinate, and yes, you really want to.]
There are lots of edge-on galaxies in the sky, like NGC 253 and NGC 4710, but this one is extraordinary. The alignment is perfect, and the disk is incredibly thin. Our Milky Way is 100,000 light years across and 2500 or so light years thick (a ratio of 40:1), but NGC 4452 looks even thinner than that; measuring off the picture I get a width-to-thickness ratio of 100:1.
Other things are obvious, too, and honestly a bit weird. For one thing, the central bulge of the galaxy is very small; in most edge-on galaxies it pokes above and below the disk like in NGC 4565, shown here. In that picture you can also see lots of dark dust; that’s actually complex organic molecules that are very efficient at absorbing visible light. They’re created when stars are born and when they die, and dust clouds tend to huddle close to the center of the disk.
[Note added later: It occurs to me there might be dust in the galaxy despite what I say in the next paragraph. That's because dust doesn't show up in the infrared very well, and one of the filters used was IR (as I note in a following paragraph). Also, the kind of camera used isn't as sensitive in the blue as it is in the IR, so that might also suppress seeing any dust that might be there. So take the next paragraph with -- haha -- a grain of salt.]
But NGC 4452 appears denuded of dust! I’ve never seen a galaxy quite so clean. I think it would actually pass the white glove test. Read More
Galaxies come in a lot of flavors. And even in the major categories (spiral, elliptical) there are sub-flavors… like barred spirals, which are truly cool and weird and awesome. Behold!
Yowza. Click to engalacticate.
That’s NGC 1365, a barred spiral about 60 million light years away in the Fornax cluster, as seen by the HAWK-1 camera on the Very Large Telescope in Chile. HAWK-1 is sensitive to infrared light, from just outside our human eye’s range to wavelengths about four times longer than we can see. Those wavelengths are pretty good (though not perfect) at penetrating dust clouds in galaxies, which block visible light. So mostly what you see in images like this one is light from stars, along with gas clouds. Where you see dark lanes is where the dust is so thick it blocks even the infrared light, too.
The two major spiral arms are obvious enough, as well as some smaller ones (called spurs) too. These are not physical spirals; stars near the center of the galaxy revolve faster around the center than ones farther out, and so if the arms were "real" they’d quickly (well, over a few hundred million years) wind up into a tight little curl. But we see spiral arms in galaxies of all ages, so we know they’re not transient, and must be stable features.
I love big, splashy spiral galaxies. They are such eye candy, and of course their breadth and scale are magnificent. Sweeping, curved arms of stars and gas a hundred thousand light years long…
One of my favorites is NGC 253, a nearly edge-on spiral that lies roughly 11 million light years away in the constellation of Sculptor. I’ve seen it many, many times, but I was honestly surprised when a new image was released by the European Southern Observatory. I’ve never seen it like this:
Wow! Click to galactinate.
As you can see, it’s tilted pretty severely to our line of sight. You can clearly see the spiral arms, and the dust lanes wrapping around the galactic center. I was amazed to see the dust appears to be thicker on the top half than on the bottom. I was even more amazed to clearly see the bar — the elongated rectangular region in the center of the galaxy! That’s almost completely undetectable in a visible light image of the galaxy: