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
Spiral galaxies are among the most beautiful objects in the Universe. Their grand, majestic nature is sweeping on a scale of hundreds of thousands of light years; their delicate arms are composed of a hundred billion stars blurred into a milky stream; and as for their cores… well, that’s a different story.
Let me present to you two surpassingly beautiful galaxies, each with a dark secret in its heart.
First is NGC 4698, as seen by Adam Block using the 0.8 meter Schulman Telescope at Mt. Lemmon in Arizona:
[Click to galactinate.]
NGC 4698 is relatively close, at a distance of 60 million light years. This image is lovely, with the faint outer arms clearly visible, the inner arms lined with clouds of dust like black pearls on a string. The core looks odd, though, which I noticed right away. It’s brighter than I would’ve expected, and appearing almost as if it’s popping right out of the plane of the galaxy.
And here’s a second spiral, M77, one with which I’m fairly familiar — I spent a long evening photographing it for an observational astronomy class in grad school. This remarkable image, however, was constructed by Andre vd Hoeven, who downloaded dozens of Hubble images of M77 from the online archive, and painstakingly assembled them into this amazing shot:
[Click to embiggen.]
Wee see M77 a bit more face-on than NGC 4698, and by coincidence it’s also roughly 60 million light years away. The red glow dotting the arms is indicative of star formation; those are vast gas clouds glowing from the heat of young, hot stars embedded in them. It too is thick with dust, and like NGC 4698 the core looks… odd. Too bright, too compact. In the high-res version you can also see a greenish glow off to the left of the core, like a searchlight shining in that direction.
So both of these galaxies look normal at a perfunctory glance, but clearly have something else going on, something not obvious that makes them special. A secret, if you will. Read More
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:
Two stories just came out that I would love to spend time writing up in full, but I’m trying to get a million things done before I leave for Dragon*Con in the morning, so I’ll be brief:
1) Astronomers using the Chandra X-ray Observatory have discovered a binary black hole: two ginormous beasts orbiting each other about 500 light years apart in the center of the gorgeous spiral galaxy NGC 3393. Each has a mass of at least one million times that of the Sun. While binary black holes in the centers of galaxies have been spotted before, this is the closest one found: a "mere" 160 million light years away!
2) A newly-discovered planet (PDF) orbiting a star just 36 light years away appears to be at just the right distance to potentially have liquid water on its surface. The planet, HD85512b, orbits a star somewhat smaller and cooler than the Sun, but close enough to it that it actually gets more heat on average than Earth does. The planet is hefty, 3.6 times the mass of the Earth, but the size is not known (you get that from transit data, which we don’t have, and it would give us an idea of the surface gravity). So we don’t know anything about it, really, but if conditions are just so, it has the best potential we know yet for a planet with liquid water. Nat Geo has a great writeup of all this.
Now, if the Universe would kindly oblige not doing anything interesting for a few more hours, I can finish packing!
The details, though, are maddening. We know, for example, that black holes spin — as odd as that may sound — but how they get that spin and how spin changes over time is elusive knowledge.
A new study has given us an idea of that now, though. Here’s how this works: we see that as matter falls into them, some black holes generate twin beams, called jets, which shoot away from their poles. We see this from black holes that form when stars explode, and we see them in the supermassive black holes that inhabit the centers of all big galaxies, too. We know that various physical features of the jets are tied to the rate at which the black holes spin, and this new study makes this connection more clear. The astronomers used computer models to correlate spin to the jets, and observations appear to confirm these models.
Two very interesting results came out of the study. Read More
A few years back I was working on creating educational products for the NASA orbiting observatories Fermi and Swift. These look at super-violent high-energy objects like exploding stars and black holes gobbling down matter. All big galaxies have supermassive black holes in their cores, and some are sloppy eaters, spewing out vast amounts of energy as the material makes The Final Plunge.
I remember finding images of one such galaxy, simply called the Circinus Galaxy, and being baffled as to why I had never heard of it or could find so little info on it. It’s only 14 million light years away, close for a galaxy! Turns out, it’s heavily obscured to visible light telescopes because it happens to lie in the plane of our own galaxy, and we have to look through lots of thick dust to see it. That dims the light a lot! But infrared light can pierce through that dust, making this an interesting object at wavelengths invisible to the human eye, colors that happen to be the specialty of NASA’s WISE spacecraft. So when astronomers took a look, well, behold!
What an awesome picture! [Click to blackholenate.]
There’s a lot to see here. Read More
I have a morality tale to tell here, but first we have to do some science. The science is part of the moral, and it’s actually rather surprising and cool. And it was reading about the science that made me chuckle, because the moral to me — as a scientist myself — was pretty obvious, but I know to others it will be as opaque as black hole.
Speaking of which…
We know that at the heart of every big galaxy lies a supermassive black hole. There’s one at the center of our galaxy — tipping the cosmic scale at 4 million times the mass of the Sun! — and one in Andromeda. In fact, looking for these monsters* was one of the key missions for building and launching the Hubble Space Telescope, a mission it had great success with.
Why those black holes are there, and so huge, is a matter of some discussion. We’re pretty sure they formed at the same time as their host galaxies themselves, and in fact helped the galaxies grow at the same time the galaxies fed the black holes material. We also know that big galaxies like our Milky Way grew to their current enormous size by literally colliding with and eating other galaxies. This would inevitably lead to the doomed smaller galaxy’s black hole falling to the center of our galaxy, where the insatiable black hole already there would merge with it, growing bigger.
When this happens, so it’s thought, matter in the form of gas, dust, and stars would also fall into the center, feeding the black hole. The matter can pile up outside the hole and get incredibly hot — observations indicate it can reach many millions of degrees, blasting out light in the form of X-rays. Galaxies like these are called active, and we see them everywhere. And many of these active galaxies are weirdly shaped, distorted, indicating they may have recently undergone a big collision. Aha! That fits the idea that colliding galaxies feed black holes and make them active.
There have been so many observations of this that it has matured to become the standard assumption: most active galaxies have recently collided with another galaxy, dumping material into the core and triggering an outburst. I can’t tell you how many papers I’ve read about this, especially when I was working on the public outreach for the Fermi satellite, which was designed to look at active galaxies.
It’s a good story. The problem is, it looks like it’s wrong.
Some 60 million light years from Earth is the monster galaxy M87. It’s a massive elliptical galaxy, one of the largest such in the nearby Universe… if you count 600 quintillion kilometers away as "nearby".
And when it comes to the Universe, I do.
It sits in the center of the Virgo cluster, a collection of roughly 1500 galaxies all bound to each other by gravity. At the heart of M87 is one of the biggest black holes ever seen: something like 6 billion times the mass of the Sun (the Milky Way has one as well, but it’s a paltry 4 million solar masses). It’s called a supermassive black hole, and it’s active. That means it’s a sloppy eater: as matter falls in to the hole, it piles up outside and forms a giant disk, which gets hot… millions of degrees hot. The tremendous heat and other titanic forces join up to blast away a huge amount of the otherwise incoming material. It’s not a nice, neat process, and when a black hole on that scale lets out a belch, it’s felt for hundreds of trillions of kilometers… as you can see in this image:
[Click to supermassivize.]
This is a composite of two images, one taken in radio wavelengths by the Very Large Array (in red) and the other in X-rays by the orbiting Chandra Observatory (in blue). The X-rays are being emitted by gas blasting away from the black hole, heated up by the disk and the magnetic fields affiliated with the hole itself. The radio waves are from gas that previously existed outside and farther away from the black hole, which is being slammed into, stirred up, and swept away by the outflowing gas.
Leon Jenkins is the President of the LA chapter of the NAACP, the organization that advocates for equal rights for black people. The work they do is fine by me, and I support their efforts. But organizations are made up of individuals, and individuals can make mistakes.
This is really one of those times. Here’s the story: Hallmark came out with a card for recent graduates, and it’s one of those deals that has a speaker in it that activates when you open it. Like all such cards it’s twee and sugary and over the top. It involves two cartoon characters with squeaky and high-pitched voices talking about how the graduate can now take over the world. It has an outer space theme to it, and what they say, well… watch/listen for yourself:
Um, yeah. It’s pretty clear to just about anyone who hears it — and doesn’t have any particular stake in the claim — that the card is saying “black holes”. The space theme is obvious enough, and black holes are a common topic. So why on Earth would someone think the card is saying “black whores”, as Mr. Jenkins and other LA NAACP members do?
In fact, there’s a good reason. What we have here is a very well-understood topic to skeptics: audio pareidolia. Read More
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.