At the University of Alabama at Huntsville, a team of scientists and engineers is looking into the possibility of identifying and deflecting Earth-endangering asteroids with lasers. Blake Anderton, an engineer at Raytheon Corp., wrote his thesis on the topic. From a UAH news release:
Anderton said his thesis discusses “a way to look at asteroids at maximum range, which means early detection.” According to his calculations, an asteroid could be characterized up to 1 AU away (1.5 x 10 to the 11 meters). Arecibo and other radar observatories can only detect objects up to 0.1 AU away, so in theory a laser would represent a vast improvement over radar.
The laser the group is working on may one day evolve into a system with asteroid-nudging capabilities. UAH’s Richard Fork, who has compiled forty years of experience with lasers, says the work goes back to research he and others performed in the 1980s at AT&T Bell Laboratories. Remote sensing is a short-term goal, but Fork says “My vision is that this system is the progenitor of the laser that could characterize and deflect asteroids.” And that would be a helpful addition to our toolkit indeed.
With all the press being given to the Large Hadron Collider under construction at CERN, it’s interesting to see that the black hole believed to exist at the Milky Way’s center — the object called Sagittarius A* — seems to be going it one better. The LHC will be able to accelerate protons to seven trillion electronvolts. But Sgr A* evidently slings nearby particles even more energetically, reaching the 100 trillion electrovolt level. Not bad for an object considered to be relatively inactive compared to black holes in other galaxies, and one explanation for the hugely energetic gamma rays streaming from that part of our galaxy.
The study in question, reported in Astrophysical Journal Letters, sees the black hole as a cosmic particle accelerator, a region where powerful magnetic fields push particles to extraordinary energies. At play is the interstellar gas extending roughly ten light years from the black hole. Fuvio Melia (University of Arizona) calls Sgr A* “…one of the most energetic particle accelerators in the galaxy, but” — and here’s the mechanism involved — “it does this by proxy, by cajoling the magnetized plasma haplessly trapped within its clutches into slinging protons to unearthly speeds.”
Image: An illustration of the idea that the black hole at the center of the Milky Way is like an extremely powerful particle accelerator, revving up protons in the surrounding magnetic plasma and slinging them into lower-energy protons with such energy that high-energy gamma rays result from the collision. The yellow line depicts a high-energy proton flung into a lower-energy proton in the hydrogen gas cloud. The green arrow represents the high-energy gamma ray that results from the proton collision. (Credit: Sarah Ballantyne).
High-energy protons, having been accelerated by their brush with the supermassive object at galactic center, then collide with protons from low-energy hydrogen, creating pions that decay into gamma rays. So here’s an explanation for some of the universe’s most exotic objects. Melia again:
“Ironically, even though our galaxy’s central black hole does not itself abundantly eject hyper-relativistic plasma into the surrounding medium, this discovery may indirectly explain how the most powerful black holes in the universe, including quasars, produce their enormous jets extending over intergalactic proportions. The same particle slinging almost certainly occurs in all black-hole systems, though with much greater power earlier in the universe.”
The paper is Ballantyne et al., “A Possible Link between the Galactic Center HESS Source and Sagittarius A*,” in Astrophysical Journal Letters 657 (March 1 2007), L13-L16. A preprint is available.
What would happen if asteroid 99942 Apophis ever hit the Earth? It’s about 1200 feet in diameter, and according to David Morrison (NASA Ames), that’s large enough to obliterate an area the size of England. The subject was under discussion at the recent American Association for the Advancement of Science meeting, and is reported capably in this Columbus Dispatch story, which quotes others on their own conclusions.
Jay Melosh, a geophysicist at the University of Arizona’s Lunar and Planetary Laboratory, said that if Apophis struck Earth, it would produce a 40-megaton blast, almost eight times larger than the most powerful nuclear bomb ever detonated. The explosion would create a crater more than 2 miles wide and obliterate buildings and bridges in a 4-mile radius. Melosh said everything around it would be buried beneath 20 inches of debris.
Nice to see a sober article discussing asteroid deflection in the popular press. Apophis probably isn’t going to make this kind of history, but the potential for getting blind-sided by an uncatalogued object is always there. Long-term thinking inevitably includes the premise of species survival, which is why a space-based infrastructure will eventually be forced upon us whether we want it in the short-term or not. Let’s hope it doesn’t take a Rendezvous with Rama-type survivable hit to make the case more emphatically.
Addendum: New Scientist covers Apophis scenarios and asteroid deflection in this recent article. Also see this post by Brian Wang on the Lifeboat Foundation weblog.
If dark energy is pushing the universe apart at an accelerating clip, when did its effects begin to be felt? One way to study that question is through the Cosmic Microwave Background, whose infinitesimal variations in density and temperature give us an idea of what was happening a scant 400,000 years after the Big Bang. We should be able to find information in the CMB about how dark energy affected the formation of galaxy clusters by comparing CMB evidence against what we see in these clusters today.
And that makes ‘first light’ at the National Science Foundation’s South Pole Telescope a noteworthy event. The 75-ft tall telescope has been under assembly and testing since November, and its February 16 test run was a success. Now the pole’s cold, dry air will allow long-term Earth-based study of the CMB with little interference from water vapor. The Sunyaev-Zeldovich effect, which distorts CMB radiation as it encounters the gases in intervening galaxy clusters, will help scientists image the gases in these clusters.
Image: Backlit South Pole Telescope in profile, with sun dog (arc and rainbow), caused by ice crystals. Credit: Jeff McMahon.
The potential data windfall from galaxy clusters is immense with this instrument. Says John Carlstrom (University of Chicago), who headed the team that tested the telescope:
“To get a meaningful constraint on dark energy through measuring galaxy clusters, you need something like this South Pole Telescope. The cluster SZ [Sunyaev-Zeldovich] signals cover small patches in the sky relative to the intrinsic variations in the cosmic microwave background. To get the necessary resolution, you need a big telescope. Now we have one.”
At an altitude of 3000 meters on the Antarctic ice sheet, the Amundsen-Scott South Pole Station must be the nearest thing to a space-based telescope on Earth. The first major project for the instrument is a survey that is expected to reveal thousands of galaxy clusters, helping us to refine our knowledge of dark energy’s effects over time. More information is available at the South Pole Telescope homepage.
Long-term thinking is a continuing preoccupation in these precincts. For if we lack the ability now to mount human expeditions to the outer planets and to push probes into the Oort Cloud and beyond, the building of our mission concepts is still vital. We go experiment by experiment, paper by paper, creating a foundation for that future. Ad astra incrementis — you get to the stars one step at a time, and as you go up those steps, you realize that each one has taken you that much farther than the last.
It can be hard to make that case heard in a culture obsessed with consumerism and immediate satisfaction, but we can shape an argument for results in the long-term that may catch the most jaded eye. Ponder that we are on the verge of nanotechnology and computing capabilities that may resolve key issues of propulsion and instrumentation. By the end of the century, we may be sending intelligent robotic probes to destinations now thought impossible. If, that is, we take the needed steps now.
At Kyushu University in Japan, Tetsuo Yasaka and colleagues are developing a fifty-year plan for building an outpost on or near Callisto, one that would control laboratories on other Galilean satellites and send probes into the Jovian atmosphere. Primarily robotic, the outpost might include human crews under the Europan ice, where Jupiter’s intense radiation would pose far less of a threat. It would exploit the potential of this environment to produce propellants and study the ocean for life.
Yasaka’s thinking is to move beyond what isolated probes can do to create a permanent human presence that can be self-sustaining and aimed at systematized exploration of the entire Jovian system. Early priorities, after creating the central node at the Callisto L2 point, would be a geophysics laboratory on Io (robotic, to be sure) and the Europan sub-surface outpost, with a station on Ganymede to follow.
An idle daydream? Projects like this will always seem so without intelligent planning, but this exercise in long-term thinking, which may eventually bear fruit in one form or another, relies on a sound methodology. Ten major items of technological development are targeted, each to be undertaken in a five-year plan that could produce near-term benefits for spinoff to other space projects and industry.
The challenges of such a project are immense. To maximize payload and minimize travel time to Jupiter, aerobraking and aerocapture methods must be used. For power, nuclear energy seems to be the first candidate, but huge deployable solar arrays may be an option even though Jupiter’s orbit is at the outer limit of solar energy use. Intelligent robotics is also crucial, and here we look to machines that are supremely adaptable to their environment. The radiation hazard must be studied as well, identifying candidate technologies for dealing with it. And so far we are only in the first five-year phase of study.
Why put intensive effort into creating a fifty year plan for a series of missions that may never happen? This is how Tetsuo Yasaka explains the project, relying on collaborations between technology developers, government agencies and academia:
The project basically is, at present, a technology project that mainly contains items related to transportation, energy and environment driven technologies, that are identi?ed as crucial to outer planet explorations. The explorations will not be carried out by the University alone. Planetary explorations will be carried out under government agency initiative, with close collaborations with academia. In case of the Jovian outpost, it will no doubt be an international project. Missions are likely proposed by academic community, which Kyushu University has strong alliance with.
You see why I bring this up. What I’m after here is a methodology that looks at goals that are not presently attainable, and sets up step-by-step methods to define and investigate the technologies that can reach those goals. This is something like the ‘horizon mission methodology’ that NASA sometimes employs to stimulate new thinking in its seminars and conferences. Present a problem that is at present impossible to solve. Then define the breakthroughs needed to make this future possible.
You wind up targeting the key gaps in our knowledge. You look at ideas on the edge and try to distinguish the viable ones from the far more numerous dead-ends. You aim at provoking discussion that leads to insight. And one day something flows from all this. I suspect Tetsuo Yasaka would be surprised if we end up with a Jovian outpost that looks like this one. But that there will be a human presence in Jupiter space — and by this I mean people or intelligent AI — seems overwhelmingly likely.
And when that happens, it will be because projects like this one at Kyushu University have started early, worked hard, and thought long-term. For more, see Yasaka, “Outpost in Jovian system—a stepwise long-term undertaking,” Acta Astronautica 59 (2006), pp. 638–643.