by Paul Gilster | Mar 22, 2007 | Deep Sky Astronomy & Telescopes |
When you can work with a deformable mirror that compensates for atmospheric distortions, wondrous things can emerge. The Gemini Observatory (Mauna Kea, HI) used such a system coupled with a laser guide star as reference to produce an image of fast-moving ‘bullets’ of gas and the wakes they leave as they move through molecular hydrogen in the Orion Nebula. Some 1500 light years away from Earth, this stellar nursery has much to teach us about the birthing of stars.
What we’re looking at appears to be the movement of clumps of gas that have been ejected from within the nebula by some kind of violent event. They’re moving outward at about 400 kilometers per second, vast gaseous agglomerations roughly ten times the size of Pluto’s orbit around the Sun. At the tip of each clump you can see the blue glow of iron atoms shock-heated by friction with the surrounding cloud. The long wakes of their motion appear as orange smudges in the image below.
Image: This composite image at infrared wavelengths was obtained using the Gemini North laser guide star system in conjunction with the ALTAIR adaptive optics system and the NIRI near-infrared imager. The image shows the Orion “bullets” as blue features and represents the light emitted by hot iron (Fe) gas. The light from the wakes, shown in orange, is from excited hydrogen gas. The images were taken at f/14 through the Fe II, H2 1-0 and K-band filters and then combined into one color composite image. The field of view of this image is about 50 arcseconds across and structure on 0.1 arcsecond (2 pixel) scales is visible. Credit: Gemini Observatory.
These are young features, their age estimated at less than a thousand years since ejection. The beauty of this work is that the imagery is precise enough for astronomers to follow developments as the bullets of gas push ever outward through the Nebula. Says Michael Burton (University of New South Wales):
“What I find stunning about the new image is the detail it shows, which was blurred out in any previous studies, revealing the structure of the bullets and their trailing wakes as they run into the surrounding molecular cloud…[S]mall changes in the structures are expected from year to year as the bullets continue their outward motion.”
Burton’s fascination is well founded, as he and David Allen (Anglo-Australian Observatory) were the first to explain the origin of the Orion bullets some 15 years ago. But beyond the bullets themselves, the exciting news is the progress being made in adaptive optics. Gemini’s system settles down the atmospheric jitter that makes stars seem to twinkle. The laser guide star it creates is an artificial reference point that allows it to measure how the atmosphere is distorting near-infrared starlight and correct for it. As we perfect these technologies, long observing runs that might otherwise prove impractical for space-born telescopes will become available to astronomers here on Earth.
by Paul Gilster | Mar 20, 2007 | Culture and Society |
I’ve been waiting for something official re the reported closing of NASA’s Institute for Advanced Concepts, but now that New Scientist is confirming the story that Keith Cowing at NASAWatch broke earlier this morning, I think it’s time to comment on this grim development. NASA will save $4 million in its annual budget by closing NIAC. That means closing a program that regularly sought ideas from people outside the agency, funded them in a first round to see if they held promise, and offered more substantial second round funding to advance the best of them still further.
Institute director Robert Cassanova has championed innovative ideas in propulsion, robotics, spacesuit design and more. In fact, NIAC-funded studies are so rich that browsing through this material could give science fiction authors ideas for years. I’ll add that Cassanova’s enthusiasm for the work was communicable. He was a great help when I was gathering NIAC material for Centauri Dreams (the book), and although he was planning retirement in any case, this loss has to be a bitter blow.
Let me quote something Dr. Cassanova told me in an interview for the book:
“Genius is in the generalities, not in the details. Look at Einstein. The generalities of his theories were where his genius was. The details developed out of much analysis by many other scientists. Einstein was known not to be a good mathematician. His genius was being able to visualize an explanation of something in nature, in recognizing some general theory that would explain something. We want people to think about the possibility of doing things in a different way.”
So much for that. We can grant the extent of NASA’s budgetary problems and empathize with its dilemmas in dealing with Congress amid continuing public apathy. But extinguishing its Institute for Advanced Concepts (especially in the context of the earlier loss of the Breakthrough Propulsion Physics program) cuts off potentially revolutionary ideas at the knees. We can fund a hazardous, aging Space Shuttle with an uncertain mission but not the kind of essential research that should embody what this agency is all about. This extraordinarily short-sighted decision leaves those committed to a human future in space shaking their heads.
by Paul Gilster | Mar 20, 2007 | Communications and Navigation |
‘Spooky action at a distance’ is still spooky no matter how you explain it. Einstein famously used the phrase to describe quantum entanglement, where two entangled particles appear to interact instantaneously even though separated in space. Now we’re talking about using the effect for communications, following the news that European scientists have proven that entanglement persists over a distance of 144 kilometers.
Fortunately for would be communicators, a pair of entangled photons can be created in a process called Spontaneous Parametric Down Conversion. Once entangled, the photons stay entangled until one of them interacts with a third particle. When that happens, the other photon changes its quantum state instantaneously. The beauty of entanglement for communications is that anyone trying to listen in on a message invariably disrupts the entangled system, a result that would be easily detectable.
The security potential is obvious in a world where so much banking information takes digital form, and where the security needs of military communications are greater than ever. But is entanglement a theoretical exercise or can it operate in real-world conditions? To find out, the researchers needed to learn not just how far the effect could travel but also how it might be affected by local conditions. Would it be possible for a ground station, for example, to communicate with an orbiting satellite? Or would the atmosphere destroy the entanglement effect?
To find out, the European team used the European Southern Observatory’s one-meter instrument on Tenerife (Canary Islands), situated 144 kilometers from an observatory on the nearby island of La Palma. The entangled pair was created on La Palma, with one photon sent toward Tenerife while the other remained at La Palma for comparison and study. The entanglement survived, implying that a ground-to-orbit connection is workable.
“We were sending the single-photon beam on a 144 kilometres path through the atmosphere, so this horizontal quantum link can be considered a ‘worst case scenario’ for a space to ground link,” says Josep Perdigues, ESA’s Study Manager. Up next: studying quantum entanglement at much greater distances, something that might be done by putting a quantum optical terminal on a dedicated satellite.
We’ll follow that mission concept as it develops. Meanwhile, theorists still have their work cut out for them. Just why does entanglement survive a journey through a medium in which it might be expected to interact with atmospheric molecules? We have much to learn about such bizarre effects, but the recent demonstration of a workable quantum computer from D-Wave Systems highlights how swiftly ‘spooky’ quantum properties are being harnessed for work in the macroscopic world around us.
by Paul Gilster | Mar 19, 2007 | Advanced Rocketry |
We’re a long way from achieving practical fusion to supply our power needs, much less fusion rockets to the stars. Just how far can be gauged by a look at current research. The principle seems straightforward: Heat hot, ionized gas to the point of ignition and you can fuse hydrogen into helium. But can you contain the plasma while you’re heating it? More to the point, can you get more power out of your device than you put in?
Most of the effort these days is going into tokamak designs that use magnetic fields to contain the plasma. But tokamaks tap plasma currents to produce at least part of the needed field. And, says John Canik (University of Wisconsin), “The problem is you need very large plasma currents and it’s not clear whether we’ll be able to drive that large of a current in a reactor-sized machine, or control it. It may blow itself apart.”
Enter the stellarator, an alternative plasma confinement method that uses no plasma currents, but one that loses energy at a high rate because the magnetic coils that generate the field are inefficient. That energy loss is known as transport, and too much of it makes fusion impossible. It would be helpful to correct that, for the stellarator brings engineering advantages in terms of designing a working fusion reactor.
Canik’s team at Wisconsin is working on a possible solution, a stellarator concept called HSX (Helically Symmetric eXperiment). It loses less energy than other stellarator designs, bringing some of the confinement advantages of a tokamak to the stellarator concept. The robustness of the magnetic field thus produced retains the energy and may make practical fusion more likely. “The slower energy comes out, the less power you have to put in, and the more economical the reactor is,” says Canik.
Image: Ungainly, isn’t it? But if it can help us toward workable fusion, we’ll live with its looks. Here we see the HSX coils and vessel on a support superstructure. Credit: University of Wisconsin.
Useful indeed, but consider this an incremental rather than breakthrough advance. The University of Wisconsin’s fusion research program has been going since the early 1960s and now includes several plasma confinement experiments. HSX’s design goes back seventeen years, a reminder that in so much of our scientific endeavor, patience is the name of the game.
Nonetheless, the latest work tweaks the confinment field interestingly, as described in this news release:
The HSX is the first stellarator to use a quasi-symmetric magnetic field. The reactor itself looks futuristic: Twisted magnetic coils wrap around the warped doughnut-shaped chamber, with instruments and sensors protruding at odd angles. But the semi-helical coils that give the HSX its unique shape also direct the strength of the magnetic field, confining the plasma in a way that helps it retain energy.
Next up is manipulating the coil design to achieve the lowest transport rate, and then figuring out ways to make the coils easier to engineer. Is a fusion generator on the (distant) horizon? The paper is Canik et al., “Experimental Demonstration of Improved Neoclassical Transport with Quasihelical Symmetry,” Physical Review Letters 98, 085002 (2007).
by Paul Gilster | Mar 17, 2007 | Antimatter |
If we need a huge particle accelerator to produce antimatter and use it only for exotic experiments, how are we ever going to ramp up production to the point where it becomes practical as a propulsion system? One answer may be that as we study the minute amounts of antimatter available for study today, we are learning how to use it in ways that are far more likely to catch the public eye, as in medicine. And treating cancer effectively — ask any patient — is anything but theoretical.
At CERN (European Organization for Nuclear Research), the Antiproton Cell Experiment (ACE) has been running since 2003. It’s an attempt to look at antimatter’s effect on cancer cells, and its results are startling. Antiprotons, it turns out, are four times more effective than protons at destroying live cancer cells. Here’s CERN’s Michael Holzscheiter on the encouraging news:
“To achieve the same level of damage to cells at the target area one needs four times fewer antiprotons than protons. This significantly reduces the damage to the cells along the entrance channel of the beam for antiprotons compared to protons. Due to the antiproton’s unsurpassed ability to preserve healthy tissue while causing damage to a specific area, this type of beam could be highly valuable in treating cases of recurring cancer, where this property is vital.”
Antimatter annihilates when it meets normal matter. And in this case, an antiproton annihilating with part of the nucleus of an atom in a tumor cell produces desirable results that multiply. The released energy is effective at destroying nearby tumor cells as well, a ripple effect not available with more conventional particle beam therapy based solely on protons. We’re still talking about clinical applications that are a decade or so out, but giving antimatter a ‘real-world’ connection boosts society’s interest in its study and may result in higher funding levels for future work.
