by Paul Gilster | Mar 7, 2008 | Outer Solar System |
Sometimes nature does what huge telescopes can’t manage. Tomorrow night, a careful amateur astronomer may be able to provide information not only about the tiny asteroid 45 Eugenia but also about the two moons that orbit it. At play is an occultation, in which these moons and Eugenia itself helpfully occlude a star for observers in various parts of the southern US and Mexico. Sky & Telescope is reporting the relevant times to be 5:42 to 5:45 UTC on March 9.
Image: Eugenia and its larger moon, Petit-Prince. With a density only 20 percent greater than water, this main belt asteroid is either a loose pile of rubble or an icy object with sparse rocky materials. Petit-Prince orbits it at a radius of 1,190 kilometers. Not shown here is the smaller moon, Petite-Princesse. The animation was assembled from infrared images of the objects. Credit: William Merline (SwRI), Laird Close (ESO), et al., CFHT.
Moons have been discovered in their dozens around asteroids ever since 1994, when the Galileo spacecraft found Dactyl, a satellite of asteroid 243 Ida. But timing observations like these can be helpful in flagging the location of the moons relative to the asteroid they circle, with an accuracy we can’t manage with our best telescopes. David Herald (International Occultation Timing Association) points to the possibilities:
“If this event is well observed, the profiles of the components will be resolved at the 1-km level, relative positions being determined to within a few hundred microarcseconds. So I encourage everyone near the predicted paths to join in the group activity and monitor this event! And remember, the uncertainty in the path location could be a good 100 km or more. So even if you are outside the predicted paths, you should still monitor the event.”
Another opportunity for amateur astronomy, whose practitioners now have a shot at making observations of such tiny objects as the delightfully named Petit-Prince and Petite-Princesse, the known moons of Eugenia (the smaller of these objects is a mere 6 kilometers across). The necessary details are on the IOTA site, which also points to David Breit’s page on the occultation, complete with maps. Even binoculars can track this event, or telescopes with an aperture of at least 2.4 inches and up. CCD cameras, needless to say, would be more than helpful.
by Paul Gilster | Mar 6, 2008 | Culture and Society |
Science fiction has brought us so many concepts for colonizing the stars over the last hundred years, everything from interstellar arks loading thousands of colonists (the sea-faring metaphor) to worldships that see generations of crewmembers live and die during their long joiurney. Suspended animation can get people through a trip that takes centuries, while robotic wardens might oversee the safe passage of human genetic material that could be converted into a colony upon arrival.
If you want to be on the cutting edge today, though, better look toward what George Dvorsky talks about in Seven ways to control the Galaxy with self-replicating probes. Here’s a novel way to colonize a distant star system: Let a von Neumann probe find a promising planet and use the matter it finds there to establish a colony and fill it with settlers. Not the kind of settler that gets out of a suspended animation tank, yawns, stretches, and then walks out onto an alien landscape, but an uploaded consciousness that would be able to take physical (robotic) form to explore the new environment.
Image: John von Neumann, shown here with technology that might have been more to his taste, the 18,000 vacuum-tube strong ENIAC. One can only wonder what the sybaritic mathematician would have made of uploaded consciousness. If only he were here to tell us.
The awakening of a consciousness in an exoplanetary setting makes for still more science fiction fodder. And it’s an interesting take on where advances in computing might take us, one demanding artificial intelligence and supercomputing powers we may achieve sooner than we expect. The colony built with such methods could be quite large because it is limited solely by computational resources, and the von Neumann probe, with its assembler technology, can take care of that lack in short order. A single von Neumann probe using these methods spreads throughout the galaxy, offering strange new alternatives to travel. How about this:
Colonization probes could also construct data receivers and transmission stations so that uploaded persons could travel as digital data streams from one point to another. Consequently, the dream of traveling at the speed of light will some day be possible.
Traveling at the speed of light as a data stream gets you where you’re going with no perceived lapse of time (to you, at least), so that the journey to Andromeda is instantaneous. Which is quite enough to chew on, you would think, but Dvorsky’s fascinating article tackles the whole subject of von Neumann probes, breaking them down into categories ranging from explorer probes to berserkers, the ultimate in malevolent technology. All are intelligent devices capable of self-reproduction via molecular assemblers. You could put together a great science fiction reading list with treatments of all Dvorsky’s categories.
Ponder, for example, ‘uplift’ probes, most familiar through the work of Arthur C. Clarke and Stanley Kubrick in 2001: A Space Odyssey. The monoliths of the movie’s beginning enable the use of tools, an extraterrestrial civilization imparting gifts to the creatures it finds on a distant world, our own. Dvorsky also notes David Brin’s Uplift series and goes on to discuss motivations for uplift and its implications:
Uplift probes could quickly bring a civilization to a post-Singularity, postbiological condition. Such a force might appear as a colonization wave that sweeps across the Galaxy, transforming all that it touches into computronium. Such a scenario has been projected by such thinkers as Hans Moravec and Ray Kurzweil.
Computronium maximizes computing power to the point where we might imagine a Dyson sphere or a Matrioshka brain — a set of concentric Dyson spheres — created to capture usable energy from a star for use in computation. If species take such a route, and if galactic colonization via von Neumann probes could be accomplished in as little as half a million years (a reasonable extrapolation), then is the absence of the computronium ‘wave’ a sign that extraterrestrials aren’t out there? Or is it a sign (as Adam Crowl speculated to me in a recent e-mail) that the wave has already passed; i.e., the notion that we are already living in a simulation gains a delightful speculative force (I don’t believe it for a minute, but then, I’m not much an admirer of the Singularity either).
My own thinking on von Neumann probes is that self-replicating technology like this is best used in Dvorsky’s category two, the Bracewell probe. Ronald Bracewell imagined probes set up in an array of communications relays and Dvorsky points to the obvious cultural example in recent times, Sagan’s Contact, where a dormant Bracewell probe awakens in the Vega system and began to transmit to Earth after receiving radio evidence that a technological civilization is nearby. Bracewell probes in our own system? The most encouraging thing that can be said about the search for such is that there is no shortage of places to look. Stable orbits around Jupiter make a certain sense.
by Paul Gilster | Mar 5, 2008 | Exoplanetary Science |
In today’s world, one of the more useful gifts for a scientist to have is the ability to save money. Enter the Jet Propulsion Laboratory’s Wesley Traub, who copes with problems like NASA’s indefinite hold on Terrestrial Planet Finder with a low-cost alternative of his own. Last year, Traub and crew experimented with the Solar Bolometric Imager, an observatory lofted by a balloon to altitudes of 35 kilometers and more. Their study of air distortions at those altitudes convinced Traub that the balloon’s movements through the stratosphere would not distort received images, and that led to speculation about doing exoplanet science close to home.
A balloon-based TPF? Hardly, but Traub does talk about imaging perhaps twenty exoplanets, according to a recent story in New Scientist. The method: A coronagraph teamed with a one to two-meter mirror. The so-called Planetscope weighs in at $10 million, making it a bargain when compared to space-based observatories, and cheap enough to tempt experimentation, even though a full-blown space mission would obviously offer far higher levels of performance.
Traub’s presentation to the American Astronomical Society’s annual meeting in January explained how Planetscope’s coronagraph could block the glare of the stars being investigated while allowing light from their planets to be detected, opening up the possibility of spectrographic studies of distant atmospheres. With both TPF and Darwin coping with budgetary issues, not to mention technological questions in need of resolution, Planetscope could become a useful stop-gap, just as coming observatories will open up new options from the ground.
Not nearly as inexpensive but nonetheless well below some Terrestrial Planet Finder estimates is another mission Traub has championed called Small Prototype Planet Finding Interferometer (SPPFI). Here we’re talking about a passively cooled two-telescope space interferometer operating at the L2 point in near- to mid-infrared wavelengths. The team investigating this one believes that it can be used to study the atmospheres of non-transiting exoplanets and perhaps taken still further:
Clearly such a mission concept has sufficient sensitivity to detect and characterize a broad range of extrasolar planets. If the telescopes are somewhat larger than has been discussed in some of the exisiting mission concepts (e.g., 1-2 m) and are somewhat cooler (e.g., < 60K) so that the interferometer can operate at longer wavelengths, it is possible for the SPPFI system to detect earth-like planets around the nearest stars. This is especially important now that there is an increasing belief that lower mass planets are very common, based on the detection of the 5.5 Earth mass planet using the microlensing approach...
A mission like this one comes with a price tag of $600 to $800 million and offers the opportunity to study not just exoplanets but the debris disks around stars we’ll later want to look at with missions like Darwin and TPF. We’re clearly ready for these next steps. Radial velocity methods have steadily improved, to the point where we can now find planets not only of Saturn mass but that of Neptune and Uranus, with improvements expected in the near future. Microlensing and transit studies both offer the chance to spot smaller, rocky worlds. Given our budgetary constraints, concepts that can take us to the next level and set the table for the breakthrough observatories we all hope for have to be affordable.
Which is why work like what Traub’s team is doing deserves your attention. Think affordability. Right now NASA has funded nineteen teams for studies for future observatories, a total of $12 million in fiscal 2008 and 2009 that includes a concept Centauri Dreams has always admired both for its technology and its budget, Webster Cash’s New Worlds Observer. Also under scrutiny is a study of direct imaging of giant planets around nearby stars using 2-meter class optical space telescopes. Study results for these latter mission ideas are expected in March of 2009.
For more on the work of Traub’s team, see Danchi et al., “Towards a Small Prototype Planet Finding Interferometer: The next step in planet finding and characterization in the infrared,” a white paper for the Exoplanetary Task Force. On 2-meter class optical space telescopes, see especially Stapelfeldt et al, “First Steps in Direct Imaging of Planetary Systems Like our Own: The Science Potential of 2-m Class Optical Space Telescopes,” also submitted to the AAAC Exoplanet Task Force (abstract). We’ll follow all these mission concepts as they make their way through the system.
by Paul Gilster | Mar 4, 2008 | Asteroid and Comet Deflection |
By Larry Klaes
Tau Zero journalist Larry Klaes now looks at recent activity in near-Earth space, where a variety of objects have turned up just this year to remind us of the potential danger of impacts on our planet. With good connections at Cornell University, Larry is our point man for Arecibo information, the more of which the better as we assess the near-Earth asteroid issue and what can be done if one of these rogue objects is found to be on a collision course.
The last two months have seen a fair number of objects from space making rather close encounters with the terrestrial worlds of our Solar System.
In late January, a small planetoid designated 2007 WD5 made a relatively close pass of the planet Mars. Astronomers had earlier projected the planetoid might actually strike the Red Planet and hoped that one of the robotic spacecraft currently in Mars orbit would be able to record the 164-foot wide rock’s impact on the planet’s surface. However, as the scientists made refinements to their information on 2007 WD5’s solar orbit, the odds of such a collision dropped from 1 in 75 to 1 in 10,000.
While there is still a chance that the space rock did hit the Red Planet, more than likely it is now circling the Sun again. 2007 WD5 is currently too small and remote for Earth-based astronomers to monitor for now, nor does this Near Earth Object (NEO) have any chance of impacting our planet in the next century or so, based on the best understanding of its solar orbit.
Had 2007 WD5 struck either world, however, it would have impacted in a manner similar to the object that struck in what is now Winslow, Arizona some 50,000 years ago. Known as Meteor Crater (though it should be more properly called Meteorite Crater), the impactor made a ground scar one mile across that is still visible today and remains a significant tourist attraction. The shock waves from the impact would have killed any living creature within twenty miles of ground zero.
Just a few days before planetoid 2007 WD5 flew by Mars, another somewhat larger object named 2007 TU24 passed by Earth just a bit further than the distance of our Moon. Despite some early concerns about a possible impact with our planet and several inaccurate and deceptive commentaries about this planetoid causing havoc with our world, 2007 TU24 proved not to be a threat. The space rock did, however, prove a boon to science with its close flyby, allowing the Arecibo Observatory in Puerto Rico to bounce radar signals off its surface in late January and early February and return images three times better than the next best radar telescope.
“We have good images of a couple dozen objects like this, and for about one in ten, we see something we’ve never seen before,” said Mike Nolan, a senior research associate at Cornell, to the Cornell Chronicle. “We really haven’t sampled the population enough to know what’s out there.”
Image: The largest single-dish telescope in the world, Arecibo proves uncommonly effective at detecting and tracking the kind of objects that in the past may have caused mass extinctions. Keeping its planetary radar in operation is crucial to planetary security. Credit: National Astronomy and Ionosphere Center/Cornell University/NSF.
One week later, another space rock labeled 2008 CT1 came within 84,000 miles of Earth, just two days after its discovery by the Lincoln Near Earth Asteroid Research (LINEAR) project at New Mexico’s White Sands Missile Range. Although 2008 CT1 is only the size of a large pickup truck and not likely to return to our neck of the Solar System until 2041, recent studies indicate that even relatively small objects impacting from space can cause major damage. The celestial body that caused the Tunguska Event, flattening many square miles of Siberian forest one hundred years ago this June, was recently determined to be smaller than previously predicted at just over 100 feet across.
In early February, Arecibo radar imaged another planetoid — 2001 SN263 — making a 7 million mile pass at Earth. Though little was known about this 1.5-mile wide space rock since its discovery by LINEAR in 2001, the planetoid turned out to be holding a major surprise: It was a triple system, the first such NEO ever discovered.
“We did not have much information about 2001 SN263 until we started observing it,” explained Nolan, who is also the head of the Solar System group at Arecibo and the assistant director for technical services at the observatory. “We chose it because it was fairly large (~2.5 kilometers in diameter) and well placed in the sky for us to be able to observe it over a relatively long interval (about 10 days). Many NEOs are visible for only a few days at Arecibo.”
To obtain the image of 2001 SN263, Arecibo transmitted a 500,000 watt radar beam towards the planetoid. The radar echo power received with Arecibo’s ultra-sensitive detectors and processed into these images totals less than a billionth of a billionth of a billionth of a watt.
The radar images depict a spherical main body surrounded by two smaller elongated companions. Nolan suspects that these two “satellites”, one of which is roughly the size of the Arecibo radio telescope, orbit the larger body, but more data is required to be certain of this. As for the composition of 2001 SN263, Nolan says that “from recent spectroscopy done by coworkers, it appears to be ‘primitive’, meaning rock and organic material that has not been heated very much.”
While Nolan and his team do not yet know how this triple NEO came to be, they do know that the planetoid will not cross Earth’s solar orbit for at least the next one thousand years. This discovery will certainly help in science’s understanding of other planetoid and cometary bodies which are also part of multiple systems and the formation and behaviors of NEOs in general.
Although certain planetoids and comets are a threat to organisms on Earth, their potential impact may also ironically save some of our planet’s lower life forms by reseeding our world or another such as Mars with terrestrial microbes.
In a new paper in the Spring, 2008 issue of the journal Astrobiology, Gerda Horneck and colleagues report on their experiments with a variety of simple organisms in surviving the shock of a celestial impact and the subsequent catapulting into space with the debris flung upwards from the collision. Their tests show that certain creatures could indeed survive such an event and reach other worlds, or return to a damaged Earth to begin a new evolution of life. Centauri Dreams‘ story on this work is here.
by Paul Gilster | Mar 3, 2008 | Culture and Society |
Ever since I was a kid watching Adventures in Paradise on TV, I’ve had a yen for islands, the more remote the better. The show had quite a pull on a young imagination, as skipper Gardner McKay sailed the waters of French Polynesia in his schooner, turning up beautiful women and adventure at most every port. The thought of someday threading through the Tuamotus or setting out for Nuku Hiva and the Marquesas made my spirit soar, and to this day my fascination with maps is undiminished.
So you can imagine how I studied the image below, and the kind of speculations it triggered. Because when you look at a map, you try to put yourself there in your mind, and perhaps no islands are more challenging to imagine than the ones pictured here. The work of San Diego middle school teacher Peter Minton (and thanks to Frank Taylor for the pointer), they’re based on Cassini imagery peering through the murk of Titan’s atmosphere at what seems to be an island group in a methane sea. Assuming, of course, that the methane/ethane mix is something more than sludge, but this is where the imagination has its own work to do.
And here is the image from which Minton worked:
Minton normally works with satellite photos of out of the way islands here on Earth, like Isla Alboran in the Mediterranean or Nukutavake Island in the aforementioned Tuamotus. Anyone with a lust for distant ports of call will want to bookmark his site. The idea of turning to Cassini imagery is brilliant and leads me to wonder what’s next for Minton. These are substantial islands, the largest almost fifty kilometers long. Below, you can see the unnamed sea that holds the islands, a vast body of liquid methane, ethane and nitrogen about the size of Lake Superior.
From Voyager to early radar imagery of Venus and now again with the Messenger mission to Mercury, we are challenged with new landscapes and the naming of places in ways that haven’t occurred in centuries. The thought of extending our mapping to extrasolar planets through the kind of space telescopes we may be able to deploy by the end of this century is breathtaking. As always, maps fire the imagination and provoke an essential human wanderlust. One day imagery of a green and blue exoplanet may spur our efforts to make the most difficult of all voyages, using technologies we have probably not yet imagined.
