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Astrobiology and the Kuiper Belt

by Paul Gilster | Oct 29, 2010 | Outer Solar System | 9 Comments

Here's an interesting bit of news from the New Horizons team. Remember that the spacecraft, having made its pass by the Pluto/Charon system in 2015, will be moving ever deeper into the Kuiper Belt. It's been the hope of mission planners that a close study of one or more objects there might be possible. Now astronomer Scott Sheppard (Carnegie Institution of Washington) has announced that he has detected the first asteroid in Neptune's trailing Trojan zone (the planet's L5 point), an area New Horizons will fly through before arriving at the Pluto/Charon binary. 2008 LC18 is not itself in range for a New Horizons flyby, but mission principal investigator Alan Stern notes its significance in a recent report on the mission's Web site: " ...its discovery shows that additional and potentially closer Neptune Trojans that New Horizons might be able to study could be discovered in the next three years." And that gives us an interesting mission extension for New Horizons, to take advantage of...

Crunching the Numbers on Earth-Size Planets

by Paul Gilster | Oct 28, 2010 | Exoplanetary Science | 30 Comments

Finding Earth-size planets around other stars is a long-cherished goal, and new results from Geoffrey Marcy and Andrew Howard (UC Berkeley) give us reason to think they're out there in some abundance. As reported in Science, the astronomers have used the 10-meter Keck telescopes in Hawaii to make radial velocity measurements of 166 G and K-class stars within 80 light years of Earth. The resulting five years of data suggest that about one in every four stars like the Sun could have Earth-size planets, although none has thus far been detected. "Of about 100 typical Sun-like stars, one or two have planets the size of Jupiter, roughly six have a planet the size of Neptune, and about 12 have super-Earths between three and 10 Earth masses," said Howard, a research astronomer in UC Berkeley's Department of Astronomy and at the Space Sciences Laboratory. "If we extrapolate down to Earth-size planets -- between one-half and two times the mass of Earth -- we predict that you'd find about 23...

Ocean Impacts and Their Consequences

by Paul Gilster | Oct 27, 2010 | Asteroid and Comet Deflection | 15 Comments

It's good to see asteroid deflection occasionally popping up in the news, thanks to the efforts of people like former astronaut Rusty Schweickart, whose efforts as co-chairman of the Task Force on Planetary Defense of the NASA Advisory Council are complemented by his work for non-profits like the B612 Foundation. Schweickart is worried about the potential consequences of even a small asteroid impact, pointing to the Tunguska event of 1908, in which 800 square miles of Siberian forest were flattened in the kind of strike that occurs every 200 to 300 years. Bigger asteroids are, obviously, a far greater danger, and while they're much rarer, they do have the capability of wiping out entire species, as may well have occurred some 65 million years ago in the destruction of the dinosaurs. In his recent New York Times article, Schweickart notes what we need to do: With a readily achievable detection and deflection system we can avoid their same fate. Professional (and a few amateur)...

‘Snowball Growth’ and the Centauri Stars

by Paul Gilster | Oct 26, 2010 | Exoplanetary Science | 10 Comments

With three groups now looking hard at Alpha Centauri for planets, let’s hope our nearest stars don’t do for us what Gliese 581 has. First we had a habitable planet in Gl 581c, then we didn’t. Then Gl 581d looked a bit promising, and may skirt the outer edges of the habitable zone, although the jury is still out. Gl 581g looked to be the winner, the fabled ‘Goldilocks’ planet, but now the evidence for it seems weak and its existence is called very much into doubt. Gl 581 keeps dealing out winners and then calling them back, a frustrating period for all concerned. What we’d like to find at Alpha Centauri, then, is something unambiguous. But while we wait for answers, the issue of how planets form in close binary systems like Alpha Centauri is under the microscope. Centauri A and B have a mean separation of 23 AU, closing to within 11.2 AU (think of another star as close to ours as Saturn) and receding up to 35.6 AU (roughly Pluto’s distance). Proxima is much further out at 13,000 AU...

Planet Formation Around Close Binaries

by Paul Gilster | Oct 25, 2010 | Exoplanetary Science | 11 Comments

Planets around binary stars fascinate me, doubtless because of Alpha Centauri’s proximity and the question of whether there are planets there. About ten percent of the planets we’ve found around main sequence stars are found in binary systems, and most of these binaries have wide separations, in the range of 100 to 300 AU. But, like Alpha Centauri, close binaries remain promising targets. I’m looking at a new paper by Andras Zsom, Zsolt Sándor and Kees Dullemond (Max-Planck-Institute für Astronomie) dealing with early stage planet formation in binaries, and they’re quick to note that planets in close binary systems put constraints on planet formation theories. After all, if we find planets in these systems, our planet forming theories have to produce satisfactory explanations for their existence. Does core accretion, then, work in these environments? We can look to close binaries with planets, systems like Gamma Cephei (separation 18.5 AU), GL 86 (18.4 AU), HD 41004 (23 AU) and HD...

Earthly Windows into Dark Energy

by Paul Gilster | Oct 22, 2010 | Exotic Physics | 6 Comments

While lamenting the budgetary problems of space-based missions like SIM -- the Space Interferometry Mission -- I often find myself noting in the same breath that technological advances have us doing things from the ground we used to think possible only from space. Make no mistake, we need to develop space-based interferometry for future studies of exoplanet atmospheres and their possible biomarkers. But it's gratifying that the next generation of ground-based telescopes using adaptive optics coupled with extremely large instruments like the Giant Magellan Telescope will also give us powerful tools for studying exoplanets. Image: An artist's rendering of the Giant Magellan Telescope in its enclosure. Credit: Giant Magellan Telescope Organization. The same holds true for another intriguing line of investigation. We've known about dark energy since the late '90s, when two groups -- the Supernova Cosmology Project and the High-z Supernova Search Team -- discovered that the expansion of...

Losing SIM: Thoughts on Exoplanetary Strategy

by Paul Gilster | Oct 21, 2010 | Exoplanetary Science | 25 Comments

For all the excitement the Kepler mission has generated, we sometimes forget its limitations. Kepler is engaged in a transit hunt for exoplanets that will help us identify not just gas giants but planets the size of our own. But it's a brute-force method, looking at a huge number of stars to identify the few whose planetary systems are aligned properly for us to see transits. And the necessary limitation is that when we do find terrestrial-sized worlds, we'll be unable to do much by way of follow-up, because most of those planets will be thousands of light years away. This is not to diminish Kepler's critical work (nor that of CoRoT), for in no other way are we currently gaining this kind of overview of the planetary environment around a wide range of stars. But Philip Horzempa reminds us in a recent post on The Space Review that we have follow-up missions in the pipeline that are now losing their funding. Specifically, the Space Interferometry Mission (known as SIM Lite in its last...

Exoplanet Atmospheres: What We Don’t Know

by Paul Gilster | Oct 20, 2010 | Astrobiology and SETI | 14 Comments

What happens in the atmosphere of a tidally locked world in the habitable zone of a red dwarf? We have solid work suggesting through simulations that habitable conditions could exist there, but it's also true that we're in the early stages of these investigations and we have no actual examples to work with. Drawing hasty conclusions is always dangerous, particularly when we're talking about the details of atmospheric circulation on a planet no one has ever seen. Take Gliese 581g. Assuming it exists -- and there is still a bit of doubt about this, although the consensus seems to be that it's really there -- we can place it in a temperature zone that would allow life. We don't know for a fact, though, that it isn't a water world, covered entirely with deep ocean, a planet that migrated from beyond the snowline into its present position. And even if it is a rocky planet with a substantial atmosphere, our simulations of atmospheric circulation only represent the best that is known today....

The Interstellar Tool Builders

by Paul Gilster | Oct 19, 2010 | Culture and Society | 21 Comments

Long before I knew what ideas for interstellar flight were out there in the literature, I always saw the idea of a trip between the stars in Homeric terms. It would be an epic journey that, like that of Odysseus, would resonate throughout human history and become the stuff of legend, even myth. In back of all that was the belief that any vehicle we could design that could carry people and not just instruments to the stars would be a 'generation ship,' in which the crew were born, raised their families, lived their lives and died while the ship, moving at maybe 1 percent of light speed, pressed on to destination. That familiar science fiction trope still has a ring of truth about it, because if for some reason we as a species decided we absolutely had to get a few human beings to Alpha Centauri, about the only option we would have for the near-term is a solar sail and a close-pass gravity assist by the Sun, and even in the best case scenario, that still works out to around a thousand...

Exploring Alcubierre’s Ideas in the Lab

by Paul Gilster | Oct 18, 2010 | Exotic Physics | 7 Comments

by Richard Obousy Physicist Richard Obousy has long been fascinated with the Casimir force, dark energy, and the stability of higher dimensions. His dissertation at Baylor University, in fact, focused on the possibility that dark energy could be an artifact of Casimir energy in extra dimensions. Now project leader of Project Icarus, Obousy here takes a look at a recent paper by Igor Smolyaninov (University of Maryland) that explores the Alcubierre 'warp drive' concept from the standpoint of material parameters. Can warp drive be modeled in the laboratory, and under what constraints? Finding the answer may yield new information about this exotic concept. As Smolyaninov says in his paper, "We will find out what kind of metamaterial geometry is needed to emulate a laboratory model of the warp drive, so that we can build more understanding of the physics involved." Fermat's principle dictates that light rays follow the shortest optical paths in media. Effectively they are geodesics, and...

NASA: The Hunt for Good Ideas

by Paul Gilster | Oct 15, 2010 | Culture and Society | 12 Comments

Is NASA going to start pushing back into the realm of truly innovative ideas? Maybe so, to judge from what Robert Braun continues to say. Braun, who joined the agency in February, is now NASA chief technologist, a recently revived office that coordinates mission-specific technologies at the ten NASA centers. This story in IEEE Spectrum notes that Braun is soliciting 'disruptive technologies' through a series of 'grand challenges.' Most of these relate to short-term space activities such as Earth observation missions, but enhancing robotics and pushing new ideas in space propulsion has obvious implications for deep space operations. From Susan Karlin's story at the IEEE Spectrum site: The grand challenges address three areas: accessing space more routinely, managing space as a natural resource, and future quests. Achieving these goals mostly boils down to improvements in spacecraft propulsion, energy use, and safety; advances in astronaut health, communication technology, and...

Dust and Fast Missions

by Paul Gilster | Oct 14, 2010 | Interstellar Medium | 26 Comments

The recent debate between Jean Schneider (Paris Observatory) and Ian Crawford (University of London) is the sort of dialogue I'd like to see more of in public forums. When I began researching Centauri Dreams (the book) back in 2002, I was deeply surprised by the sheer energy flowing into interstellar flight research. True, it lacked focus and tended to be done by researchers in their spare time, as opposed to being funded by universities or government agencies, but I had not realized that the topic itself was under such serious investigation by so many scientists. All those fascinating concepts, from laser sails to fusion runways, were the catalyst for this site, where keeping an eye on the ongoing discussion is the order of the day. In an era of short-term thinking and instant gratification through one gadget or another, taking a longer look at the human enterprise and where it is going is an imperative. One way to do that is to consider whether our species has a future in deep...

Interstellar Flight and Long-Term Optimism

by Paul Gilster | Oct 13, 2010 | Culture and Society | 40 Comments

It's fascinating to watch the development of online preprint services from curiosity (which is what the arXiv site was when Paul Ginsparg developed it in 1991) to today's e-print options, hosted at Cornell and with mirrors not just at the original Los Alamos National Laboratory site but all around the world. Then, too, the arXiv is changing in character, becoming an early forum for discussion and debate, as witness Ian Crawford's comments on Jean Schneider's Astrobiology paper. We looked at Crawford's criticisms of Schneider yesterday. Today we examine Schneider's response, likewise a preprint, and published online in a fast-paced digital dialogue. Schneider (Paris Observatory) focuses here on nuclear fusion and antimatter by way of making the case that interstellar flight will be a long and incredibly difficult undertaking. A bit of context: Schneider's real point in the original Astrobiology piece wasn't to offer a critique of interstellar flight ideas, but to call attention to the...

Interstellar Flight: The Case for a Probe

by Paul Gilster | Oct 12, 2010 | Missions, Uncategorized | 26 Comments

Back in May I looked at Jean Schneider's thoughts on what we might do if we discovered a planet in the habitable zone of a nearby star. In an article for Astrobiology called "The Far Future of Exoplanet Direct Characterization," Schneider (Paris Observatory) reviewed technologies for getting a direct image of an Earth-like planet and went on to discuss how hard it would be to get actual instrumentation into another solar system. His thoughts resonate given recent findings about Gliese 581g (although the latest data from the HARPS spectrograph evidently show no sign of the planet, a startling development as we investigate this intriguing system). Whether or not Gl 581g exists and is where we think it is, Schneider's pessimism about getting an actual payload into another solar system has attracted the attention of Ian Crawford (University of London), who is quick to point out that astronomical remote-sensing, especially for biological follow-up studies of initial biomarker detections,...

A Look Into Titan’s Haze

by Paul Gilster | Oct 11, 2010 | Outer Solar System | 11 Comments

Voyager's controllers thought so much of Titan that when Voyager 1 approached Saturn and the choice arose between sending it on to the outer planets or taking a sharp jog off the ecliptic to view the enigmatic moon, they chose the latter. We all know the result: Titan remained as mysterious as ever, its surface shrouded in orange haze. But you can see why they needed that look. Here was a moon that was large enough to be a planet, with a thick atmosphere and all kinds of speculation about what was on its surface. No wonder Titan was the most tempting of targets, and one of huge scientific value. These days we routinely get Cassini imagery from Titan flybys, and the place has gained definition. I remember once asking Geoffrey Landis, having read his superb 2000 novel Crossing Mars, whether Mars had become more or less an everyday place to him, like Cleveland (he lives there, working at NASA GRC). And it was true: After you study and survey and write novels about a place, it does...

Waiting Out New Horizons

by Paul Gilster | Oct 8, 2010 | Outer Solar System | 9 Comments

The outer Solar System has always been something of an obsession for me, to the point where as a kid, I used to haunt the libraries looking for books on planetary science. Absurdly, I had the notion that even though little was known about places like Triton and Pluto, I might just stumble upon the one book that had details known to no one else. So I would work my way through the shelf, finding the odd speculation here, the small insight there, but it wouldn't be until Voyager's 1989 Neptune flyby that some of these places began to take on actual shape for all of us. All the Myriad Ways And then there was Larry Niven's 'Wait It Out,' a short story from the Known Space universe that was originally published in 1968, in a wonderful collection called All the Myriad Ways. Here a team of astronauts on the surface of Pluto is marooned and the narrator, after his comrade has died, removes his helmet, freezing to death so quickly that his brain becomes a superconductor, so that a strange form...

Advanced Propulsion in Context

by Paul Gilster | Oct 7, 2010 | Culture and Society | 36 Comments

I want to run through the particulars on the upcoming 2010 Advanced Space Propulsion Workshop at the University of Colorado in a moment, as the deadline for abstracts is still three weeks away for those who are thinking of submitting papers. But looking through the presentations at conferences like this one -- it's sponsored by the Jet Propulsion Laboratory, the US Air Force Research Laboratory and Glenn Research Center's In-Space Propulsion Technology Project -- I always think about where we stand in terms of long-term goals. And something Caleb Scharf said in a recent post on Life, Unbounded resonated in those terms. Scharf (Columbia University) had been discussing the list of Mars launches, going all the way back to 1960 with the failed Soviet Marsnik 1, subsequent Sputnik 22, Zond and Cosmos launches, various Mariner attempts, and, of course, the eventual Viking Landers. It's a list of failures interspersed with triumphs like the current rovers and orbital vehicles like Mars...

Rethinking Alien Encounter

by Paul Gilster | Oct 6, 2010 | Culture and Society | 84 Comments

by Larry Klaes Larry Klaes wraps up his two-part essay on our attitudes towards extraterrestrials by looking at how the subject has been treated in the past, and speculating on the scenarios that might bring disaster. Do Earth-shattering depictions of space invasion reflect what people really believe, or are they merely a form of escapism? Either way, they tell us something about ourselves as we confront the possibility of contact. For those who may still wonder and question just how much weight the words of the famous cosmologist Stephen Hawking hold for the concept of alien intelligences and their potential reactions to encountering humanity, consider this: A new science fiction film coming out this November titled Skyline has recently premiered its theatrical trailer, which you can view here. The trailer begins with the line: "On August 28th, 2009, NASA sent a message into space farther than we ever thought possible... in an effort to reach extraterrestrial life." Now it is true...

Why Do We Fear Aliens?

by Paul Gilster | Oct 5, 2010 | Culture and Society | 59 Comments

By Larry Klaes Just how we would react to the reception of a signal from an extraterrestrial civilization is an increasingly controversial question, and one filled with import as we take the SETI search in proposed new directions. The ongoing Royal Society meeting in Chicheley (UK) probes the issue, with panel discussions on whether or not we should be sending our own broadcasts to the stars, and presentations exploring the import of extraterrestrial life on the future of humanity. It seems a good time, then, for Larry Klaes to have a look at the question in this, the first of a two-part essay that analyzes our attitudes not so much about signals from the stars as their senders. Several months ago, the famous British physicist and cosmologist Stephen Hawking shared his views on extraterrestrial intelligences (ETI) with the intelligent beings of the planet Earth. This was done in no small part as a way to gain publicity for his new television science series, Stephen Hawking's...

A Tour de Force of Planetary Discovery

by Paul Gilster | Oct 4, 2010 | Culture and Society, Outer Solar System | 18 Comments

Steven Vogt (UC-Santa Cruz) is suddenly the buzz of the blogosphere, though not in ways he might have intended. The designer of the HIRES spectrometer that made the detection of Gliese 581g possible, Vogt can claim pride of place as the discoverer of the first near-Earth mass planet found in the habitable zone of its star. But he's also taking his lumps for saying that he could all but guarantee life on that planet. An unwise call, as many commenters here have noted. Perhaps even more unwise is his hope to name the new planet after his wife, Zarmina. Centauri Dreams has nothing against the notion of naming celestial objects for loved ones, but caution should always be the byword. Suppose, for example, that Mrs. Vogt, fed up with publicity and tired of the company of astronomers, should surprise her husband by leaving him. Vogt's ex would be forever enshrined in the celestial sphere, a taunting presence whenever the poor man thought of the Gl 581 system. Such a scenario happens in...

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In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For many years this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image courtesy of Marco Lorenzi).

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