Astronomers have just announced that tiny Pluto has a fifth moon! It was discovered using the Hubble Space Telescope:
You can see it in that image (click to enhadesenate) in the green circle. Pluto was targeted by HST for several observations in late June and early July, and P5 – also called S/2012 (134340), the moon’s designation until it gets a proper name – was seen moving around the tiny world. This image is from July 7.
As moons go, it isn’t much: it’s probably only about 10 – 25 kilometers (6 – 15 miles) across, making it one of the smallest moons detected in the entire solar system. That’s actually pretty amazing, given Pluto was 4.7 billion km away (2.8 billion miles) when these images were taken!
Pluto was observed in part to look for more moons. In 2015, the New Horizons probe will zip past Pluto, and scientists want to know as much about the system as they can before it gets there. The odds are low of them hitting any of those moons – space is big, and the moons and spacecraft are small – but a) better safe than sorry, and 2) if there are more targets to observe we want to know now so they can be added to the itinerary!
Observations like this are good for discovering moons and getting their locations, but size is a different matter. Literally. We know how far away the moon is, and how bright, but it’s far too small to directly get the size. Its diameter has to be estimated by assuming how reflective the surface is. If it’s dark like coal, it has to be bigger to be so bright, and if it’s shiny like ice, it’s smaller. That’s why we don’t know P5’s size to even within a factor of 2! But once New Horizons zips past, it may be able to nail down the size far better.
The first moon of Pluto, Charon, was discovered in 1978. Nix and Hydra were found using Hubble in 2006, and the fourth moon just last year, in 2011.
As for the argument about Pluto being a planet or not, this will no doubt provide grist for the mill. However, number of moons does not a planet make; Mercury and Venus have none and they’re planets. Mars has twice as many as Earth does, but it’s not twice the planet! And many very small asteroids have moons, too.
My feelings about this are on record: the word "planet" is not and can not be defined; it’s a concept, not a definition. It’s like the word "continent": it’s more of an idea than something you can rigidly define. There is no sharp border that you can use to divide objects into planet and not planet.
So I actually don’t care if you call Pluto a planet or not. It is what it is: a very cool object, perhaps the biggest in the Kuiper Belt of frozen icy comet-like bodies past Neptune. It’s an oddity, since it’s so bright, and yes, has so many moons.
And it’s absolutely worthy of study, no matter what you call it.
Image credit: NASA, ESA, and M. Showalter (SETI Institute)
Stars are one of the fundamental building blocks of the Universe. Huge, hot, and powerful, they emit energy that can be detected across vast reaches of space. For as long as they live (so to speak) they glow with a fierce luminosity.
And even when they die they can announce their presence in weird and wonderful ways.
Meet U Camelopardalis, just such a dying star about 1400 light years from Earth:
[Click to doomsdaymachinenate.]
U Cam is a red giant, a star that was once like the Sun but has gone much further along its evolutionary path. Our Sun is fusing hydrogen steadily into helium in its core, providing warmth and light for us. U Cam ran out of hydrogen in its core long ago, and began fusing helium into carbon. Then it even ran out of helium as a fuel! The core is now essentially an extremely hot ball of carbon, squeezed by pressure to within an inch of its life. There’s still helium outside the core, and gets so much heat from the core’s radiation that it’s fusing in a thin shell. Think of it like a very hot skin around an orange.
This helium fusion is ridiculously dependent on temperature. Increase the heat just a wee bit and the fusion rate increases madly, generating huge amounts of energy, which get dumped into the outer layers of the star on very short timescales. And by "short" I mean like years. Not millions of years. Just years.
When this happens the star swells immensely and ejects its topmost layer, like a solar wind on cosmic steroids. This event doesn’t last long, maybe a century or so, then it subsides. But that shell of ejected gas expands out from the star, eventually dissipating over millennia.
And that’s where U Cam is right now. Not long ago its core underwent one of these paroxysms, and the star blasted out the shell of material you can see in this Hubble Space Telescope image. Measuring the expansion rate, it looks like this shell was ejected about 700 years ago, and the event only took 50 years to unfold! Because these events don’t last long compared to the life of the star, it’s rare to see them. U Cam is one of the best of only a handful of such stars known.
In the image you can see how thin the shell is, indicating the event happened rather quickly (if it took a long time the shell would be thicker). I’ll note that the total mass of the shell is only about a tenth the mass of the Earth! It’s spread out over so much volume of space that it’s barely more dense than the vacuum surrounding it.
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
Life must suck for HD 189733b.
It’s a planet orbiting the star HD 189733, about 63 light years from Earth. It’s similar to Jupiter, being slightly more massive and slightly bigger. Unlike our own big brother, though, HD 189733b is far closer to its parent star, orbiting just about 4 million kilometers (about 2.5 million miles) above its surface! That means the cloudtops of the planet are at a scorching 840°C (1500°F), so hot that the atmosphere of the planet is getting blown away by the star itself, creating a comet-like tail of gas escaping from the planet.
And now, adding insult to injury, astronomers have discovered that the star is prone to cosmic hissy fits — and this may actually blow torch even more air from the planet.
[Illustration by NASA, ESA, and L. Calçada]
This pretty nifty: the researchers targeted the star and planet using Hubble in 2010 and didn’t see anything amiss. In 2011, though, they observed it with Hubble again, but also used NASA’s Swift satellite, which is sensitive to high energy emission like extreme ultraviolet and X-rays. They happened to be looking when the star erupted in a massive flare, quickly quadrupling its brightness in X-rays alone. And because the planet is so close to the star, it took the full brunt of this event, its atmosphere puffing up and actually getting blasted away into space by the fierce light from the star!
Just a few hours later, as seen from Earth, the planet passed directly in front of its star (like Venus did during its transit earlier this month). The atmosphere by this point was really streaming away from the planet in the aftermath of the flare, and was also blocking a bit of the star’s light. In the Hubble data the astronomers not only detected that absorption, but they could measure it to see how much hydrogen the planet was losing. It turns out something like 1000 tons of hydrogen was screaming away from the planet every second! And that’s a lower limit; they could only detect neutral hydrogen — that is, atoms that still held on to their electrons. There was probably plenty of ionized hydrogen they couldn’t detect.
NASA put out a short video that explains this as well:
It’s generally said that discoveries in science tend to be at the thin hairy edge of what you can do — always at the faintest limits you can see, the furthest reaches, the lowest signals. That can be trivially true because stuff that’s easy to find has already been discovered. But many times, when you’re looking farther and fainter than you ever have, you find things that really are new… and can (maybe!) be a problem for existing models of how the Universe behaves.
Astronomers ran across just such thing recently. Hubble observations of a distant galaxy cluster revealed an arc of light above it. That’s actually the distorted image of a more distant galaxy, and it’s a common enough sight near foreground clusters. But the thing is, that galaxy shouldn’t be there.
This picture is a combination of two images taken in the near-infrared using Hubble. The cluster is the clump of fuzzy blobs in the center left. The small square outlines the arc, and the big square zooms in on it.
The cluster is unusual. It’s at a distance of nearly 10 billion light years away. Clusters have been seen that far away, so by itself that’s not so odd. The thing is, it’s a whopper: the total mass in all those galaxies combined may be as much as a staggering 500 trillion times the mass of the Sun, making this by far the most massive cluster seen at that distance.
But that arc… First, things like this are seen pretty often near clusters. They’re gravitational lenses: the gravity from the cluster bends the light from a more distant galaxy in the background, bending its shape into an arc. See Related Posts below for lots of info and cool pictures on these arcs. In this case, I’ll note the shape of the arc implies the biggest galaxy in the cluster, the one right below the small square, is doing most of the lensing.
But here’s the problem: the galaxy whose light is getting bent has to be on the other side of the cluster, and that cluster is really far away. Note only that, the galaxy has to be bright enough that we can see it at all. Combined, this should make an arc like this rare. Really rare.
So rare, in fact, that it shouldn’t be there at all! The astronomers who did this research worked through the physics and statistics, and what they found is that the odds of seeing this arc in this way are zero. As in, what the heck is it doing there at all?
You’d think that with all our fancy equipment and technology, all the nearby galaxies in the Universe would’ve been spotted by now. But it turns out that’s not the case. Some galaxies are very faint — small, with few stars — making them tough to find even when relatively speaking they’re in our neighborhood.
So say hello to our newly-discovered neighbor, UGC 4597!
[Click to galactinate.]
UGC 4597 is a dwarf galaxy. Galaxies like our Milky Way have billions or hundreds of billions of stars, but dwarf galaxies have stars numbering in the millions. That’s why it remained undiscovered until just a few years ago — it turned up in a survey taken in 2008! Astronomers were looking for dwarf companions to the splashy spiral galaxy M81 located about 12 million light years away, and dinky UGC 5497 showed up.
The image above was taken by Hubble in late 2009. Of course, in this shot it looks obvious enough, but this only shows a teeny portion of the sky. Because it’s so close to us, the entire M81 group of galaxies covers an area of the sky something like 20 times the size of the full Moon — thousands of times the size of this diminutive dwarf. That’s how it remained undiscovered for so long.
The image is a combination of two separates shots, one in visible light and one in near-infrared. The stars look very blue, with very few being red. Without a third image taken in bluer light it’s hard to be completely sure, but the color here most likely means that most of these stars are young, created in a wave of star formation a few million years ago. Just above and to the right of center of the core of the galaxy is a reddish patch; I thought initially that might be a gas cloud of some sort, but now I suspect it’s a background galaxy. In the full-res version of the picture you can see dozens of distant galaxies littering the scene, typical for a Hubble picture. They’re most likely hundreds of millions and even billions of light years away, far, far in the background.
That bright star on the right and the fainter one on the left are probably stars in the foreground, in our own galaxy. Sometimes that fact gets me even more than the rich science of the galaxies themselves: the depth of time and space we see in images like this. Nearby objects like local stars, medium-distance objects like neighborhood galaxies, and then mind-crushingly distant galaxies so far away that the light we see from them left when the newest evolutionary invention on Earth were organisms with more than one cell!
Astronomy may be all about looking out into the Universe, but it’s the perspective on ourselves that always stirs my mind.
ESA/Hubble & NASA
I figured I was done posting Venus Transit pictures, but I should’ve realized I hadn’t heard from Thierry Legault yet. And as soon as I saw his name in my email Inbox this morning, and before I even opened it, I knew I’d have at least one more picture to show you.
And I was right. Thierry is a master astrophotographer, and he’s not one to just let an astronomical event go by without figuring out some way to make it even cooler. He traveled to northeast Australia to view the Venus transit… not just because it had a good view, but also because from there, he could see the Hubble Space Telescope transiting the Sun at the same time! On June 6th, at 01:42:25 UTC, he got this amazing shot:
Holy wow! [Click to doubletransitenate.]
You can see Venus as the big black circle, as well as dozens of sunspots. But you can also see multiple images of Hubble as it zipped across the Sun, circled in the image above. Orbiting the Earth, Hubble moves across the sky so quickly that it crossed the Sun in just under a second. Blasting his DSLR away at ten frames per second (and with an exposure time of only 1/8000th of a second per frame) Thierry managed to get 8 shots of Hubble silhouetted against the Sun.
Here’s a bit of a close-up:
I added the arrows to help you see Hubble. The orbiting telescope was about 750 kilometers (450 miles) away from Thierry when he took these pictures (it was not directly overhead), so details on Hubble are too small to capture, but it can be seen as a black dot.
Theirry’s done this before, too: in January 2011, he got an astonishing picture of the space station crossing the Sun during a partial solar eclipse! His ability to time these events and get pictures like these is nothing short of amazing.
He also says he got more pictures, too, including some of Venus just as it was entering the Sun’s face. Hopefully he’ll have those available soon! In the meantime, click the links below under Related Posts to see more of his ridiculously cool photos.
Image credit: Thierry Legault, used by permission.
– China’s space lab has a spot in the Sun
– Doomed ROSAT captured in video
– Atlantis, one last time in the Sun
– SERIOUSLY jaw-dropping pictures of Endeavour and the ISS!
– INSANELY awesome solar eclipse picture
I have no shame in admitting I love face-on spiral galaxies. Scientifically, of course, they’re fascinating; spread out in front of us are all the inner workings of a galaxy. It’s like having an X-ray of human body in front of you, making it easier to understand anatomy.
But their beauty… well. The scope and grandeur of a face-on spiral is unparalleled, I think, in astronomy, or perhaps any field of science. But don’t take my word on it. See for yourself.
[Click to galactinate, or get a 1900 x 1200 desktop image.]
This is the wonderful nearby spiral M101, and is a composite of no fewer than four orbiting observatories! It has images from Hubble, Spitzer, Chandra, and GALEX. These represent (in order) observations in visible light (shown as yellow in the picture), infrared (red), X-ray (purple) and ultraviolet (blue).
Each shows a different aspect of the galaxy. Visible light shows stars and gas, infrared indicates warm dust, X-ray show hot gas and energetic objects like supernovae and black holes, and ultraviolet is where young stars glow and light the gas around them. Each observation is incredibly useful to a scientist, but combining them together makes them even more powerful.
The things to look for are where colors overlap, and where they don’t overlap. For example, in the outer arms you can see dust and gas and young stars all together, showing where stars are born. In the inner regions of the galaxy the infrared and visible images are next to each other, parallel spirals. Dust blocks visible light, so where there’s lots of dust there’s little light we can see, and vice-versa.
You have to be careful interpreting images like this, though. The outer arms, for example, are blue. You might think this means they’re only giving off ultraviolet light. But you have to account for the different telescopes’ field of view, exposure times, and more. Each of those affects what you see no matter what the galaxy itself may be doing. Images like the one above are useful, even important, but it’s also important to remember their scientific limitations.
But artistically? That’s a different matter. All together.
Image credit: X-ray: NASA/CXC/SAO; IR & UV: NASA/JPL-Caltech; Optical: NASA/STScI
Today is the 22nd anniversary of the launch of the Hubble Space Telescope. I worked on Hubble one way or another for a decade or so, and it changed not just my life, but the lives of astronomers around the world, and of course forever altered — for the better! –how the public viewed of astronomy.
To acknowledge this, below is a repost of my "Ten Things You Don’t Know About Hubble", first put on the blog in 2010, and which I think still holds up. And what better way to celebrate this observatory’s anniversary than to get to know it a little better?
On April 24, 1990, the Space Shuttle Discovery roared into space, carrying on board a revolution: The Hubble Space Telescope. It was the largest and most sensitive optical-light telescope ever launched into space, and while it suffered initially from a focusing problem, it would soon return some of the most amazing and beautiful astronomical images anyone had ever seen.
Hubble was designed to be periodically upgraded, and even as I write this, astronauts are in the Space Shuttle Atlantis installing two new cameras, fixing two others, and replacing a whole slew of Hubble’s parts. This is the last planned mission, ever, to service the venerable ‘scope, so what better time to talk about it?
Plus, it’s arguably the world’s most famous telescope (it’s probably the only one people know by name), and yet I suspect that there are lots of things about it that might surprise you. So I present to you Ten Things You Don’t Know About the Hubble Space Telescope, part of my Ten Things series. I know, my readers are smart, savvy, exceptionally good-looking, and well-versed in things astronomical. Whenever I do a Ten Things post some goofball always claims they knew all ten. But I am extremely close to being 100% positive that no one who reads this blog will know all ten things here (unless they’ve used Hubble themselves). I have one or two big surprises in this one, including some of my own personal interactions with the great observatory!
April 24th marks the 22nd anniversary of Hubble’s launch into space. To celebrate it, NASA and ESA released this devastating panoramic view (also available here) of the mighty star-forming region 30 Doradus:
Yegads. [Click to embiggen, or get the 4000 x 3200 pixel version, or grab the ginormous 267 Mb 20,323 x 16,259 pixel version. There’s also a way cool zoomable image too.]
30 Dor is a vast, sprawling, and chaotic region located in the Large Magellanic Cloud, a dwarf irregular galaxy that orbits our Milky Way. Even though it’s about 170,000 light years away it’s so bright it’s easily visible using binoculars (if you happen to live in the southern hemisphere or not far from the equator). The reason it’s so bright is that this stellar nursery is churning out thousands of stars, and some of them are the massive, hot, and blue type. These flood the surrounding gas with ultraviolet light which makes the gas glow.
In fact, those young stars are so luminous and energetic they’re eating away the cloud from the inside out! Those big cavities you see are where the light and fierce winds of subatomic particles blown from the stars are slamming onto the gas, pushing it outwards. The edges of the cavities are bright because that’s where gas piles up, and shines more brightly.
In fact, the folks at Chandra released a similar version of this image, except they added observations from that observatory, which detects X-rays (as well as an image using Spitzer which sees in infrared). X-rays are emitted from extremely hot gas, and as you can see in the image inset here (click to embiggen) the cavities are filled with X-ray emitting material (colored blue in the image). I wrote more about this in a post when a similar image was released.