Astronomers working with Fermi — a mission that is mapping the sky in gamma rays — have just released a new catalog of objects detected by the spacecraft. They’ve re-analyzed two years worth of data and have found nearly 2000 objects blasting out this super-high-energy form of light.
[Click to enhulkenate, and see a labeled version.]
The map is set up in galactic coordinates, so the Milky Way itself runs across the center. There are a lot of gamma-ray sources in our galaxy, most of which are bright simply because they’re close. Others are actually luminous sources like the Crab Nebula, various pulsars, and other violent objects. The map is very similar to one released by Fermi a while back, but this new one is more sensitive, and can see fainter objects.
About half the detected sources are active galaxies: distant galaxies with supermassive black holes at their hearts, actively gobbling down matter and spewing out vast amounts of energy in the process (black holes are sloppy eaters). The folks at Goddard Space Flight Center put out a nice, short video explaining this:
On June 11, 2008 — three years ago today — NASA launched the Gamma-ray Large Area Space Telescope into orbit:
Fermi — as it was renamed once it reached orbit, after the great Italian scientist Enrico Fermi — is designed to observe gamma rays, the highest energy flavor of light. Gamma rays are only emitted from the most violent events in the universe: black holes gobbling down matter, exploding stars, antimatter particles annihilating each other, and so on. Fermi surveys the sky day after day, returning gobs of data to waiting scientists.
I was involved with Fermi when it was still called GLAST. Long before launch, I signed on to do education and public outreach for GLAST at Sonoma State University. Along with our team, I wrote web pages and helped create educational activities — including classroom lessons, a card game, a paper model of GLAST, a planetarium show, a PBS NOVA episode… we even built a small observatory near the University to augment GLAST observations! You can find all this on the SSU Fermi website.
Fermi has been a very successful mission, and I’m proud to have done my small part for it. And I guess I’m still doing it; technically, writing this blog post is EPO. So happy birthday, Fermi! You’ll always be GLAST in my heart.
On March 28, 2011, NASA’s Swift satellite caught a flash of high-energy X-rays pouring in from deep space. Swift is designed to do this, and since its launch in 2004 has seen hundreds of such things, usually caused by stars exploding at the ends of their lives.
But this time was hardly "usual". It didn’t see a star exploding as a supernova, it saw a star literally getting torn apart as it fell too close to a black hole!
The event was labeled GRB 110328A –a gamma-ray burst seen in 2011, third month (March) on the 28th day (in other words, last week). Normal gamma-ray bursts are when supermassive stars collapse (or ultra-dense neutron stars merge) to form a black hole. This releases a titanic amount of energy, which can be seen clear across the Universe.
And those last two characteristics are certainly true of GRB 110328A; it’s nearly four billion light years away*, and the ferocity of its final moments is not to be underestimated: it peaked at a solid one trillion times the Sun’s brightness!
Yegads. I’m rather glad this happened so far away. That’s not the kind of thing I’d like to see up close.
Although initially cataloged as a GRB, followup observations indicated this was no usual event. The way the light grew and faded seemed to fit better with a star getting torn apart. And what can do that to an entire star? A black hole. So instead of the star in question forming a black hole, it apparently literally fell victim to one!
The observations indicate the black hole in question may have as much as half a million times the mass of the Sun, meaning it’s very probably a supermassive black hole in the very center of a distant galaxy. Hubble Space Telescope observations (not yet released to the public) also place the event very near the center of a galaxy, which is consistent with this scenario.
So what happened?
This week is the semi-annual meeting of the American Astronomical Society, the largest society of professional astronomers in the US. The January meeting is always huge, and always has a lot of news flooding from it like the collimated jet from a supermassive black hole. The big news stories I’ve written about the past couple of days have come from there, and I’ve been scrambling to keep up. But that’s proving to be difficult, so instead of my usual Pulitzer-level reporting of astronomy news, here are some links to stories that will probably interest you. And if you’re on Twitter you should be following the awesomeness that is Pamela Gay, aka StarStryder, as she writes live from the floor of the meeting (and blogs about it, too).
A very cool announcement from the orbiting gamma-ray observatory Fermi: thunderstorms on earth generate this high-energy form of light by creating antimatter. Yes, antimatter. This idea has been around for a while — I remember thinking about it years ago when I worked on the education and outreach for Fermi — but the scientists finally nailed down the specifics, and it’s pretty amazing. Not enough there to power a starship (and it might be hard to bottle it anyway), but still. Wow.
The Planck satellite is designed to look at the background radiation of the Universe in unprecedented detail. While it may not see any signatures by The Ancients (man, I’m ticked Stargate:Universe was canceled) it just released a whole lot of science, and Sean Carroll at Cosmic Variance has links to some of the science and scientific papers.
This news came out a little while ago but I didn’t cover it at the time, and it’s cool enough that it deserves to be covered. I got it from my friends with NASA’s Fermi satellite outreach group. I used to work on Fermi outreach before the satellite launched and was still called GLAST (Gamma-ray Large Area Space Telescope), and it was fun trying to come up with lesson plans and educational efforts based on gamma rays (the Hulk came up a lot).
Anyway, one thing Fermi can do is measure the exact time when high-energy gamma rays hit its detectors. Not too long ago, photons from a distant explosion slammed into Fermi, and it found that all these photons arrived essentially simultaneously from the event, irrespective of their energies.
So what? So, Einstein was right. Check it out for yourself:
Basically, the idea is that some quantum mechanics theories propose that space is irregular, foamy, and bumpy on incredibly small scales, and this means the speed at which photons travel may change very slightly if they are more or less energetic. The difference is so small that it takes very long trips to detect it — imagine two cars traveling at 50 versus 50.5 kph: after a few seconds you’ll hardly see any difference, but over an hour they’re separated by half a kilometer. So the longer the trip, the easier it is to measure.
After 7 billion years, if those specific QM theories are right, two photons should arrive at very different times, but Fermi found that the high energy gamma rays hit Fermi less than a second after the low energy ones. This means that space really is smooth, or at smooth at scales smaller than predicted by those quantum theories. QM is still a solid model for the Universe — after all, solar panels, computers, and nuclear bombs do work — but this means that we need to rethink certain aspects of them.
I love hearing stuff like this. We have lots of ideas on how the Universe works, but we need observations of the Universe to know if we’re traveling down the correct path or not. Fermi has shown us that some of these paths lead to dead ends, and we need to look elsewhere for our journey to continue. And I will guarantee that not only will that journey go on, but we’ll find ever-more roads to investigate as we travel.
One of the secondary goals of the Fermi gamma ray satellite is to look for the signature of dark matter. One idea for dark matter is that it’s composed of weird (and as yet undetected) particles called WIMPs (weakly interacting massive particles). A very odd property about them is that they are self-annihilating: when two of them touch, they turn into energy (and other, more easily detectable particles). When I first read about this several years ago I was pretty excited, because this is finally a testable hypothesis about dark matter.
My fellow Hive Overmind blogger and astronomer Sean Carroll writes that it’s possible Fermi has done just this. The data are not conclusive, but very provocative nonetheless. He has the details.
But I can’t resist adding that on The Big Bang Theory a few weeks ago, Raj and Sheldon were investigating building a detector to look for this very type of dark matter. I wrote David Saltzberg, the science advisor (whom I met on the set last month when I was visiting LA; more on him and that at a later date) and told him this, and he noted that I was right. Well, how about that! It had to happen sometime. Now, to publish…
It’s a (Bruce) banner moment for NASA’s new Fermi satellite: it’s found a pulsar that emits only gamma rays.
Brief background: when a massive star explode, its core collapses. If it has enough mass, the core shrinks down into a black hole. If it doesn’t have quite that much oomph (if it has about 1 – 2.8 times the mass of the Sun) it forms a weird object called a neutron star. As massive as a star but only a few kilometers across, a neutron star is incredibly dense, rapidly rotating, and has a magnetic field intense enough to give you an MRI from a million kilometers away.
OK, I made that last one up, but in fact it sounds about right. The point: neutron stars are seriously awesome, right on the edge of matter as we understand it.
The supercharged magnetic field channels a tremendously powerful flow of energy away from the star in twin beams like a lighthouse. And, like a lighthouse, as the star rotates these beams sweep around. If they’re aimed at Earth we see a pair of pulses every time the star spins around once. So, duh, we call these special neutron stars pulsars. You can see a way cool animation of this on NASA’s Conceptual Image Lab web page.
Usually, the beams from these pulsars contain light from all (or nearly all) across the electromagnetic spectrum. We seem them in radio waves, visible light, ultraviolet, even X-rays and some in gamma rays. The processes that create these beams are pretty fierce and weird, and the type of light emitted depends on the process. However, in general, if we see high energy light (like X- and gamma rays) from a pulsar, we tend to see it in lower energy light (optical and radio) as well.
But Fermi found an oddball! Located about 4600 light years away in the constellation of Cepheus, CTA-1 is a supernova remnant, the expanding debris from an exploding star. But that expanding junk is only from the outer layers of the detonated star: the core collapsed down into a neutron star, and that’s what Fermi detected. This newly discovered gamma-ray-only pulsar spins three times per second — think on that; an object with the mass of an entire star spinning at that rate! — and is blasting out gamma radiation with 1000 times the Sun’s entire energy output.
And all of it in super-high energy invisible gamma rays. The Hulk has nothing on this pulsar.
Actually, let’s pause for just a sec. Is it sunny outside? Good. Go outside, and hold your hand up. Feel the warmth? That’s just a bit of optical light warming your hand. Now think about how much energy is falling over the entire Earth itself, a gazillion times the size of your hand. Now think about how much energy the Sun is emitting in all directions; the entire Earth only intercepts about one-two billionths of that light. Now think about one thousand times that much energy. Now think of all that energy being only in the form of DNA-shattering gamma rays.
Yeah, now you’re getting it. This object is seriously freaky.
We know of about 1800 pulsars, and all of them emit radio waves. All but this guy. It’s a brand new category of object (well, a sub category, but still), a new character on the cosmic stage. But why does it only emit gamma rays? Hey, good question. I don’t know the answer (and the press release doesn’t say, in fact). I suspect the answer right now is, we don’t know. This object was only discovered a little while ago, and worse, gamma rays are really difficult to study. That’s why we launched Fermi in the first place! Worse even than that, without being able to look at this object in radio, optical, or any other form of light really hobbles our ability to study it.
For now, I think we’ll have to rely on Fermi’s observations and then look at theoretical models. I imagine there will be astronomers all over the world pouncing on this, trying to figure out how the magnetic fields of the star can be so choosy (maybe they’re elitist).
But until then, as usual, I have to wonder: if we only just now found this object, what the heck else is floating around out there just waiting for us to find?
Pulsar image credit: NASA.