A few years back, when I was working on using NASA satellite data to create educational materials for kids, we had this idea of using the steady beats from pulsars in a song. Pulsars are the rapidly-spinning über-dense fantastically-magnetic collapsed cores of exploded stars. As they spin, they emit beams of matter and energy that sweep out into space much like a lighthouse beam, and we see a blip of light when that beam passes over us.
Some pulsars spin hundreds of times per second, some take several seconds to spin once. If you take that pulse of light and translate it into sound, you get a very steady thumping beat with very precise timing. So making it into a song is a natural thought.
But we certainly didn’t take it as far as the German band Reimhaus did, making a music video out of it! They used several pulsars for their song "Echoes, Silence, Pulses & Waves". So here’s the cosmic beat:
Pretty clever. Lots of other people have turned cosmic phenomena into sounds and music, including the Perseid meteor shower, the Phoenix Mars Lander descent, the Earth’s aurorae, and even the aurorae from Saturn!
Image credit: NASA. Tip o’ the magnetar to Elkin Fricke for sending me the link to the video.
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:
Astronomers using the Chandra X-Ray Observatory may have found evidence for a young black hole: it was born in a titanic explosion just 31 years ago.
Black holes form when massive stars explode. The core of the star collapses, and if it’s massive enough (more than about 3 times the mass of the Sun), the gravity of the core can crush it down into a black hole.
Enter Supernova 1979c, a star that exploded in the nearby galaxy M100. About 50 million light years away, M100 is a lovely face-on spiral galaxy in the constellation Coma Berenices. SN1979c was discovered in — duh — 1979, and has been heavily studied for years since it was so bright, making it easy to see.
SN1979c was an interesting event, even for something as mind-numbingly violent as a supernova. The star that exploded was right on the edge of being massive enough to create a black hole; the total mass of the star was about 20 times the mass of the Sun, with a core of just about 3 solar masses. The question is, was the star big enough to create a black hole, or would the core collapse to form an incredibly dense neutron star?
Chandra observations may have answered this question. Read More
A thousand years ago, and 6500 light years away from Earth, a high mass star exploded. An octillion tons of gas blasted outwards at speeds of thousands of kilometers per second, forming tendrils and wisps as it raced away. At the center of the conflagration, the core of the star had collapsed into an ultradense object called a neutron star. It has the mass of the Sun crammed into a ball only 20 – 30 km (12 – 18 miles) across, and is spinning at a rate of 30 times per second.
All this happened a long time ago. The debris is what we now call the Crab Nebula, and is one of the best-studied objects in the sky. And that’s a good thing, because even now the Crab is capable of throwing tantrums… and we can see it when it does!
This image is a brand spanking new shot of the heart of the Crab Nebula taken by the Hubble Space Telescope. And by new, I mean it was taken on Saturday, October 2! It’s a bit hard to see what’s going on, so I created an annotated version:
The pulsar is labeled. It’s sitting right at the center of the gas cloud, which extends way beyond the edges of this picture. As the pulsar spins, it emits a fast stream of particles that act like a wind, compressing the gas in the nebula and creating those circles of light. They look elliptical because the whole system is tilted, and you’re seeing it like a DVD held at an angle. From what I can tell, the bottom left is the side toward us, and the upper right is farther away, as if we’re looking down on it.
In mid-September, just a couple of weeks ago, several orbiting observatories noted that there was an increased amount of gamma rays coming from this part of the sky. Gamma rays are the highest energy form of light, and there aren’t many sources in the sky that can create them at all, let alone in quantities that can be seen. The Crab is the brightest continuous gamma-ray source we know, and so it was immediately put on the Most Wanted list.
Every year, this gets harder.
Not that deciding what pictures to use in 2006, 2007, or 2008 was all that easy! But astronomy is such a beautiful science. Of course it has scientific appeal: the biggest questions fall squarely into its lap. Where did this all begin? How will it end? How did we get here? People used to look to the stars asking those questions, and coincidentally, for the most part, that’s where the answers lie. And we’ll be asking them for a long time to come.
But astronomy is so visually appealing as well! Colorful stars, wispy, ethereal nebulae, galactic vistas sprawling out across our telescopes… it’s art no matter how you look at it. And our techniques for viewing the heavens gets better every year; our telescopes get bigger, our cameras more sensitive, and our robotic probes visit distant realms, getting close-up shots that remind us that these are not just planets and moons; they’re worlds.
So every year the flood of imagery takes longer to sort through, and far longer to choose from. And the choices were really tough! This year leans a bit more toward planetary images than usual, but that’s not surprising given how many spacecraft we have out there these days.
I don’t pick all these images for their sheer beauty; I consider what they mean, what we’ve learned from them, and their impact as well. But have no doubts that they are all magnificent examples of the intersection of art and science. At the bottom of each post is a link to the original source and to my original post on the topic, if there is one. If you disagree with my picks, or think I’ve missed something, put a link in the comments! All the pictures have descriptions, and are clickable to bring you to (in most cases) much higher resolution version. So embiggen away!
And welcome to my annual Top Ten Astronomy Pictures post. Enjoy.
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.