When I picture an exploding star in my head — which I do unsurprisingly often — the imaginary mental detonation I picture is symmetric. That is, it expands like a sphere, getting bigger in all directions equally.
Supernovae are actually not like that though. Stars are messy affairs, and when massive ones explode they tend to have internal factors that distort that nice, smooth expansion. One big factor is that the actual point of explosion is off-center in the star, not at its exact heart. That can create a massively asymmetric explosion, blasting vast amounts of material and energy off to one side.
Mind you, the core itself in such a star still collapses to become a super-dense neutron star (or a black hole), but the sideways nature of the explosion can give a kick to the leftover ball of neutrons. Quite a kick. In fact, the energies are so titanic that an off-center supernova explosion can blast the neutron star in the other direction, screaming away from the explosion site like a shell out of the muzzle of a battleship gun.
And now astronomers may have found the most extreme example of this: what looks to be just such a neutron star barreling away from a supernova at high speed:
[Click to Chandrasekharenate.]
This image is a combination of observations from the XMM-Newton and Chandra X-ray observatories, the Digitized Sky Survey, and the 2MASS infrared survey. It shows the supernova remnant SNR MSH 11-16A, located about 30,000 light years away. The purple glow is from X-rays emitted by the gas superheated to millions of degrees by the exposion.
But look off to the right. See that comet-looking thing? I’ve put a close up of it here. You can see a dot at the head of the "comet": astronomers think that might be the runaway neutron star from the explosion that created SNR MSH 11-16A! It’s hard to know for sure, but a lot of things add up to make me think they’re right.
The most obvious is that tail of gas pointing right back to the center of the supernova gas cloud. A hot, young neutron star blows out a high-energy wind of subatomic particles called a pulsar wind, and that pushes against gas floating out in space. As a runaway neutron star blasts through space, it would leave a glowing trail like that. The X-rays appear to be coming from a single, tiny point, just what you’d expect for a neutron star, and observations using optical and infrared don’t see it; again, just what you’d expect since neutron stars are tiny and don’t glow visibly. They’re brightest in X-rays due to their phenomenally strong magnetic fields whipping particles around at high energies.
The fainter tail to the side is something of a mystery, though. Apparently things like this have been seen before, but it’s not clear what’s causing it.
Knowing the distance to the supernova remnant we can get its size, which, together with its expansion rate, tells us that it’s something like 15,000 years old. If that dot is the ejected neutron star, it’s screaming away from the explosion site at a mind-numbing 10 million kilometers per hour (6 million mph) — fast enough to cross the entire United State in two seconds flat! Yegads.
Other runaway neutron stars have been seen moving away from supernovae at high speeds, but none this fast. Again, this has not been confirmed to be the neutron star in question, but if it is, it handily holds the speed record for such an event. Mind you, this star probably has about the mass of the Sun: over an octillion tons!
Can I get another "yegads" from the congregation?
Images like this show me that my mental images of some phenomena need to be updated. We like to simplify in our heads, and that’s fine if it helps us get a grip, a basic understanding, of a complex event. But we have to remember that the Universe is weird and complex and sometimes gleefully bent on crushing our preconceptions. That might make some people uncomfortable, but it fills me with joy. Who wants a boring Universe where we easily understand everything?
Weirdness is way more fun.
Image credit: X-ray: NASA/CXC/UC Berkeley/J.Tomsick et al & ESA/XMM-Newton, Optical: DSS; IR: 2MASS/UMass/IPAC-Caltech/NASA/NSF
At 16:00 UTC June 13, 2012, the NuSTAR X-ray observatory began its successful journey into orbit! The satellite was launched using a Pegasus rocket, a smaller vehicle that is literally dropped from an airplane and blasts away into space. This method saves a huge amount of fuel by starting the rocket a few kilometers above the ground. [The image shown here is from a different Pegasus drop and is for explanatory purposes; I'm hoping to get some nice images of the actual NuSTAR launch soon.]
NuSTAR (NUclear Spectroscopic Telescope Array) is designed to detect high-energy X-rays emitted by some of the most violent objects in the Universe: exploding stars, matter falling into black holes, and magnetars (super-magnetic neutron stars that are capable of fierce blasts of energy).
X-ray astronomy is a lot harder to do than regular-old visible light astronomy. For one thing, our air absorb X-rays, so we have to launch telescopes into orbit to see these objects at all.
For another, at these high energies, it’s not possible to focus X-rays in a normal way. Photons of visible light bounce off of mirrors, so we can focus them to a point and see distant objects clearly. X-rays are different, though. Think of them as little bullets zipping along; if they hit a mirror they’ll penetrate right through it! So instead of using a reflective mirror, X-rays can be focused by letting them graze against a gently angled sheet of metal, like skipping a rock on the surface of a lake.
So X-ray observatories like Chandra, XMM-Newton, and NuSTAR use very long cylindrical mirrors. But not precisely cylinders; they gently taper at one end a bit like a thimble. X-rays graze these cylinders and bounce at a shallow angle, coming to a focus. The problem with this is that the angle is so shallow it takes a long path (called the focal length) to get the X-rays to a focus. So the telescopes have to be many meters long.
However, to fit on the diminutive Pegasus rocket, NuSTAR has to be only 2 meters long. Engineers solved this length problem in a very cool way: an extendable boom, like an accordion, that expands after launch and lengthens the spacecraft to over 10 meters! At one end of the extended mast are the mirrors, and at the other end are the detectors, as in the drawing above.
I’ll note I worked on NuSTAR a few years back. When I was at Sonoma State University we developed educational activities based on NASA missions. We were asked to work on the original proposal for NuSTAR to NASA, so my boss Lynn Cominsky and I wrote the original Education and Public Outreach part of the proposal, and once it was accepted I wound up writing a lot of the verbiage for the NuSTAR educational website as well.
NuSTAR has a bit of a checkered history. I wrote about this a while back; in 2006 NuSTAR was abruptly canceled just before the final proposal was submitted to NASA (and I was, um, fairly angry about that), then reinstated a year or so later. But now NuSTAR is in orbit after a wonderfully perfect launch, and I’m very, very happy.
My congrats to the NuSTAR team, especially to Dr. Fiona Harrison — to the best of my knowledge the first female Principal Investigator of a NASA astrophysics mission — on finally getting this important mission into space and peering at some of the most interesting objects in the Universe!
Image credits: NASA/JPL-Caltech/Orbital; NASA/JPL-Caltech
[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.]
I’m fond of saying that the Orion Nebula is one of the biggest, most active star forming regions in the Milky Way galaxy. It has enough gas to form thousands of stars like the Sun, and it’s one of the brightest and closest such gas clouds in the sky.
But, it turns out, Orion is a piker. Or a pike. Because behold: The Dragonfish Nebula!
[Click to ennebulenate, or if you're feeling frisky, grab the huge 7000 x 5500 pixel 26 MB version!]
The Dragonfish nebula — named for its resemblance to a terrifyingly toothy deep-sea fish — is, like its namesake, a monster. It’s something like 450 light years across… compare that to the Orion Nebula’s 12-15 light year width and you start to see how huge this thing is. It’s also incredibly massive: it may have a total mass exceeding 100,000 times the Sun’s mass, and may contain millions of stars!
Incredible. Even from other galaxies, it must be one of the most obvious features in the Milky Way. Yet, ironically, it’s very difficult to see at all from Earth. It’s located over 30,000 light years away, on the other side of the galaxy. There’s a vast amount of interstellar material (like dust) between us and it, absorbing its light, so in optical light it’s essentially invisible. But infrared light can pierce that fog, and the image above was taken using NASA’s Spitzer Space Telescope, designed to look in the infrared.
Astronomers used a different infrared telescope to look at the individual stars in the nebula, and found that it has an incredible 400+ O-type stars, the most massive stars that can exist. These stars are young, hot, massive, and blast out ultraviolet light. That’s what’s making this huge gas cloud glow, and in fact the cloud is expanding under the influence of the terrible flood of radiation. Worse, those stars will eventually explode in the next million years or so, one after another, blasting out radiation and material that will dwarf even what they’re putting out now. That will eventually tear through the nebula, ramming it, causing parts of it to collapse and form new stars, and other parts to dissipate entirely.
We’re safe where we are, tens of thousands of light year away. Too bad! In a million years, that’ll be quite a show.
Image credit: NASA/JPL-Caltech/Univ. of Toronto
I am very pleased to write that the Nobel Prize for physics this year has been awarded to three astronomers for their discovery of dark energy — a still-mysterious phenomenon that is causing the expansion of the Universe to accelerate.
Saul Perlmutter, Brian Schmidt, and Adam Riess are sharing the award. Back in 1998, Saul and Brian headed up two rival teams trying to observe very distant exploding stars, hoping they would yield better numbers for how fast the Universe expanded. Adam was on Brian’s team, and led the work on finding a way to try to understand the behavior of the supernovae. To everyone’s surprise, the data indicated the Universe was not just expanding, but expanding faster every day — it was accelerating.
Something must be pushing on the very fabric of space itself, causing it to expand ever-faster. We don’t now what it is, exactly, but we call it dark energy, and over the past 12 years, more and more observations have piled up showing that this stuff really is out there.
If you want background info on all this, see the Related Posts section below; there are plenty of links to articles I’ve written on this topic. The folks at Hubble also created a video describing dark energy and what it means for the Universe.
This is very exciting for lots of reasons. First, of course, it’s nice to see an astronomical topic win what is considered the top prize in science. Second, because I predicted it would years ago (not that this was all that difficult to see coming!). And third, for personal reasons, because I know all three of these men. I worked with Brian and Adam back in the day; the project Brian headed up to observe distant supernovae was part of a project using Hubble to observe supernovae in general, and I worked on a different aspect of it. Adam and I were both grad students at the time; after I got my PhD I went to work on a different Hubble project, and Adam stayed with the team, cracked the supernova code, and now has a Nobel Prize.
I suspect that was the right move for him.
All three of these men have worked for a long, long time on this problem, essentially devoting their lives to it. It’s very, very nice to see that pay off. It’s richly deserved!
- The Universe is expanding at 73.8 +/- 2.4 km/sec/megaparsec! So there.
- News: dark energy stunts your growth
- The Universe is expanding at 74.2 km/sec/Mpc
- Hitting the gas
- The Universal expansion revisited
- What astronomers do
- AAS Post #6: The cosmological not-so-constant
Well, it’s been a while coming, but I’m pleased to let y’all know that the third and final episode of "Bad Universe" will air on The Discovery Channel tomorrow, April 19, at 11:00 a.m. Eastern (US) time — but of course, check your local listings.
The episode is entitled "Death Stars", and is about the effects of solar flares and nearby supernovae. Like the other two, this was a lot of fun to put together, though the trip to Sandia Lab still haunts me a bit… but I won’t give that away. You’ll just have to see. I actually haven’t seen the final cut since we put it together late last year, so to be honest when I watch it tomorrow it’ll be a bit like seeing it again for the first time.
Speaking of which, my daughter will be in school when it airs, so I won’t watch it until we can see it as a family. That means I won’t be live-tweeting or anything like that.
And to answer the inevitable question: I don’t know if the network is picking it up as a series or not. I expect the ratings of the airing tomorrow may play into that, so tell a friend! Or tell a few dozen.
I hope you like it, and have at least as much fun watching it as I did making it.
Last weekend I was in NYC attending the Northeast Conference on Science and Skepticism, aka NECSS. It was a lot of fun, as I kinda figured it would be. Skeptic conferences usually are! And of course it was a chance to catch up with a lot of old friends.
Attendees are writing their opinions of the meeting all over the place (like here, here, and here for starters). I’ll spare you the recap, which would boil down to how awesome my talk was, and cut to the chase which is to thank Michael Feldman from the New York City Skeptics, and all the folks from the New England Skeptical Society for inviting me and throwing such a fab conference.
I’d be remiss, though, if I didn’t include this little bit of funnery. Skeptical singer songwriter and BA friend George Hrab was at NECSS. On Geo’s last album, "Trebuchet", he wrote a tune called "Death from the Skies" — based on the brilliant book of the same name. He plays the funky beat, and I read statistics of getting killed by various astronomical events. We performed this song live both at Paddy Reilly’s, a bar where Geo had a gig, and to close out the ceremonies.
Here’s the recording of the latter, which is pretty laid back considering how many octillions of Joules of energy I’m talking about:
And what the heck, here we are at the somewhat more rambunctious bar the night before:
See? If you go to skeptic meetings you can experience stuff like this live. It’s way too much fun.
There are photos of NECSS popping up all over the place (search Flickr), including for example a nice set by Bruce Press. I also like this shot of Geo and me taken by Brian Engler. Apparently I had just stubbed my toe.
NECSS really is a terrific event. I hope to see you all there next year!
It’s been a couple of days since the foofooraw involving Betelegeuse, 2012, and media laziness took place. As you may recall, a site in Australia made some dubious connections between 2012 and the red supergiant star Betelgeuse exploding, which you may imagine I took a fairly dim view on. As bad as that was, it got worse when The Huffington Post weighed in, adding their own nonsense to the story, misattributing parts of the story and making even more faulty connections to 2012.
The story went viral rapidly. Other media venues quickly picked up on it, furthering the nonsense without doing any independent investigation of it. Happily, not everyone got it wrong; I’ll note that the first venue that apparently got it right was Fox News, who linked to an earlier article I wrote about Betelgeuse.
I was also contacted by Jesse Emspak from International Business Times, who asked me specific questions about it and wrote a very well-written and factually accurate article about all this, doing something that made my heart sing: not just presenting the real science we could get out of a Betelgeuse supernova, but making that the focus of the article! As it should be. Kudos to him and IBT.
Stories like 2012 and nearby supernovae are sexy, easy to sell, and get eyeballs on a webpage. It’s the devil’s bargain to write about them even on a skeptical astronomy blog; it can reinforce bad science in people’s minds, or it might put a spotlight on something that could otherwise wither and die on its own (which is why I didn’t write about this story until HuffPo posted it). It’s also amazing to me how some media — some actual, mainstream news sources — didn’t do any real fact-checking before putting up links to HuffPo. It once again reinforces what I learned long ago: keep a very skeptical frame of mind when reading or listening to the news. If they can mess up something as simple as this, then what else are they getting wrong?
What does a half million galaxies look like? Something like this:
Whoa. That’s a part of a huge image just released by the Canada-France-Hawaii Telescope Legacy Survey Deep Field #1, a ginormous mosaic of the night sky… and by ginormous, I mean GINORMOUS. It covers a solid square degree of sky — 5 times the area of the full Moon — and tips the scale at a whopping 370 megapixels! It took 5 years and several hundred hours of observing time with the 3.6 meter telescope on top of Mauna Kea to get this massive mosaic.
The image itself may look cool and all, but the true power comes when
you give in to the dark side you use the interactive zoom feature. You can surf the entire mammoth 370 million pixel image, zooming in on galaxies galore. And you won’t run out of objects to investigate any time soon: there are an estimated 500,000 galaxies in the image. Like the Hubble image I posted about yesterday, almost everything you see in the image above is a galaxy, not a star.
The images were taken to look for very distant supernovae. It was the investigation of these far-flung stellar explosions that led astronomers to determine the Universal expansion is accelerating, and to postulate the mysterious dark energy that powers this phenomenon. The CFHT is being used to map the same area of the sky over and over again, looking for the tell-tale blobs of light that mark the spots of a distant, dying suns. The more of these we see, the better we can nail down the physical characteristics of the cosmic expansion, and of the dark energy about which we know so little.
Of course, astronomers will squeeze a lot of science from this and other images… but it’s also OK to simply scan and pan through them at home, too, marveling that the Universe is so deep and so deeply beautiful.
For more deep and gorgeous images like this, see Hubble Digs Deep to See Baby Galaxies, The Milky Way Bulges with Cannibalized Corpses, Hubble Pokes at a Galactic Bulge, or just search in the Pretty Pictures category of this blog.
When Galileo first turned his telescope to the sky, almost exactly 400 years ago, he could not possibly have known what he was starting.
Today, four centuries later, we’ve come a long, long way. To celebrate the anniversary of Galileo’s telescopic revolution, NASA’s Great Observatories — Hubble, Spitzer, and Chandra — have released a jaw-dropping mosaic of the very heart of the Milky Way galaxy. Behold!
This image is nothing less than a heroic effort of astronomical artistry. It’s a chunk of the sky 38 x 14 arcminutes across, or about half the size of the full Moon, and it’s aimed right into the core of our galaxy. See the bright spot just to the right of the center? Buried in there behind light years of dust and gas is the monster of the Milky Way, a black hole with four million times the mass of the Sun. But even that is dwarfed by the 400 billion solar mass heft of the entire galaxy.
There is so much going on in this image it’s hard to know where to start. But first… the Hubble images are in the near-infrared, with a wavelength a little more than twice what the eye can see (1.87 microns for those playing at home). That’s represented in the image as yellow. Spitzer contributed observations in four infrared wavelengths (3.6, 4.5, 5.8, and 8.0 microns), and those are depicted in red. Chandra sees X-rays which are normally written as units of energy, but to remain consistent with the other two images, they were at wavelengths of 0.0005, 0.00025, and 0.00016 microns, and are shown in blue.
What does all this mean? Different objects emit light at different characteristic wavelengths. Warm dust, for example, emits strongly in the infrared. Stars and warm gas emit visible and near-infrared light. Violently heated gas, affected by huge magnetic fields or shocked by colossal collisions glows in X-rays. So this image is a polychromatic view of the crowded downtown region of a bustling city: our galaxy.
You might want to look at an annotated version of this image so you can get your bearings. It’s worth it!
The huge arches of gas on the left are actually the edges of gigantic molecular clouds (dense nebulae where stars are born), lit up by the torrential blast of light from a clutch of massive stars nearby. This clot of stars, called the Arches Cluster due to the arcs it excites, can be seen as a small spot glowing blue just to the left of center in the picture. Don’t be deceived by its diminutive appearance: the Arches cluster has thousands of superstars in it, each dwarfing our Sun, and each capable of sleeting out vast amounts of radiation that lights up the gas surrounding it. Were this cluster much closer than its 25,000+ light year distance, it would blaze in our sky like a beacon. Replace the Sun in our solar system with just one of those stars, and the Earth would be fried beyond the capability of any life to survive. You might as well try living in the flame of an arc-welder.
Below and just to the left of the Arches is a clumpier, more twisted arc of gas called the Sickle. That’s a giant cavity being carved out of dense gas by the Quintuplet cluster, the pinkish glow in its center. It’s another nursery of stars like the Arches cluster, which is also blasting out light and stellar winds which eat away at the gas enveloping it. The Pistol Star resides there, perhaps one of the most massive stars in the Milky Way.
And there’s more! The blue glow on the left is from an X-ray binary called 1E1743.1-2834, what is probably a massive star being orbited by either a neutron star or a black hole. Matter is being stripped from the star and piling up outside the collapsed companion, where it gets heated up to millions of degrees and emits X-rays.
Supernovae remnants dot the image, as do stars, filaments of gas, clouds of dust, and more. This picture is an astronomer’s dream, a map of everything someone might want to visit with a starship — as long as the shields are at full strength. This image is also a map of violence, turbulence, and unrest… a typical scene, so we think, of any normal spiral galaxy like ours. And our Galaxy’s center is considered quiet by astronomers! Some are far worse.
But this is home for us. It’s a place of unimaginable fury but also astonishing beauty… and we see it now as we do because we have dared to examine the world around us, to use tools we invent to peer closer, to magnify the tiny, to extend our eyes into realms we once didn’t even know existed. And every time we do — every single time — we find more questions, more puzzles, more things to examine.
And we find art. Galileo wasn’t the first to turn his telescope to the sky, nor was he the first to record what he saw. But he was the one who made everyone see what he did, and for that, all these years later, he is owed a debt of gratitude.
M81 and M82 are bright nearby galaxies; you can spot them with binoculars easily in the northern sky, and they are a mere 12 million light years from us (for comparison, the Milky Way Galaxy is 100,000 light years across, so if you think of the Milky Way as a DVD, M81 and M82 would be about 14 meters away). These two galaxies interacted a couple of hundred million years ago, and the gravitational interaction drew out long tendrils of gas (which is very common in colliding galaxies).
Astronomers examined this bridge of material using Hubble, and found clusters of stars in it. That was totally unexpected; the gas was thought to be too thin to form stars! Amazingly, many of the stars are blue, indicating they are young (blue stars burn through their fuel much more quickly than redder stars. This means that the gas is still forming stars, even 200 million years after the collision!
In the image below, almost all the stars you see are young blue stars formed in the aftermath of that titanic collision. The reddish stars are stars in our galaxy, and the bigger objects are distant background galaxies.
Most likely, the stars formed when turbulence in the tendril caused local regions of denser gas, which could collapse to form stars. Before these observations, it wasn’t really thought it was possible to form stars in the regions between galaxies, so this is an interesting new find.