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All Quiet Around Gliese 581

by Paul Gilster | Jun 1, 2012 | Exoplanetary Science | 31 Comments

When you're looking for signs of an extraterrestrial civilization, you can take two basic approaches. Think back to Frank Drake's initial SETI experiment at Green Bank in 1960, when because of limited resources and time he chose specific targets: Epsilon Eridani and Tau Ceti. The choice made sense at the time because both were nearby stars and SETI, fresh off the classic paper "Searching for Interstellar Communications" by Philip Morrison and Giuseppe Cocconi, was just beginning to define a methodology. Drake studied his targets near the 1.420 GHz frequency -- the 21 centimeter hydrogen line -- that the authors had suggested. Of course, sky surveys are also possible, of which SETI@home may be the most widely known. Here the idea is to make no assumptions whatever about the location of a SETI signal and observe the entire sky. SERENDIP (Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations) is an attempt, for example, to analyze radio telescope data...

Is Our Civilization Detectable?

by Paul Gilster | May 31, 2012 | Astrobiology and SETI | 69 Comments

I haven't even finished the first line of this post and I'm already in a digressive mood. The mental sidetrack comes from yesterday's talk about the Square Kilometer Array, whose primary installations are now to be built in both South Africa and Australia. By observing an object through many instruments simultaneously, astronomers can use the technique called interferometry to combine incoming data and emulate a much larger instrument. The SKA's sensitivity promises to be high enough to allow the detection of possible leakage radiation from another civilization, which prompted me to recall a quote I had buried in my archives: "I know perfectly well that at this moment the whole universe is listening to us -- and that every word we say echoes to the remotest star." The words are those of Jean Giraudoux, a French writer and diplomat whose plays, written between the two world wars, gained him an international audience (Christopher Fry was among the admirers who adapted Giraudoux's work...

Thoughts on the Square Kilometer Array

by Paul Gilster | May 30, 2012 | Deep Sky Astronomy & Telescopes | 16 Comments

We now know that the vast collection of radio dishes and antennae that will become the Square Kilometer Array (SKA) will be built on two sites, with the majority of dishes in Phase 1 (beginning in 2016) being constructed in South Africa, and further dishes added in Australia as the project develops. The SKA is to be a radio telescope of unprecedented sensitivity capable of sky surveys at frequencies from 70 MHz to 10 GHz. A SKA news release notes that "All the dishes and the mid-frequency aperture arrays for Phase II of the SKA will be built in Southern Africa while the low-frequency aperture array antennas for Phase I and II will be built in Australia." Combining the signals from the project's dishes, mid-frequency aperture arrays and low-frequency aperture arrays will offer a telescope with a collecting area equivalent to a dish with an area of one square kilometer, a truly formidable observing platform. Phase 1 construction will involve about 10 percent of the array and will...

A Longer, Heavier Bombardment

by Paul Gilster | May 29, 2012 | Asteroid and Comet Deflection | 8 Comments

We know that the early Earth was a violent place, but just how violent? The so-called Late Heavy Bombardment is thought to have occurred from 4.1 billion to 3.8 billion years ago, likely the result of asteroids being destabilized in their orbits by shifts in the orbits of the outer planets. That model is self-limiting, with the unstable asteroids being depleted over time and the Late Heavy Bombardment winding down, and it matches the dating of rocks from the lunar basins that show vivid evidence of the battering both Earth and Moon took. But as I mentioned last week, the question of the length of the Late Heavy Bombardment is in play, with two papers in Nature suggesting that heavy impacts may have continued for a much longer time, perhaps half of the Earth's history. William Bottke (Southwest Research Institute) and team are suggesting that during this early period, the inner edge of the asteroid belt was just 1.7 AU from the Sun -- in a region called the E-belt, a largely extinct...

Impacts Spreading Life through the Cosmos?

by Paul Gilster | May 25, 2012 | Asteroid and Comet Deflection | 49 Comments

Still catching up after the recent series on antimatter propulsion, I want to move into some intriguing work on panspermia, the idea that life may spread throughout a Solar System, and perhaps from star to star, because of massive impacts on a planetary surface. Catching up with older stories means leaving some things unsaid about antimatter -- in particular, I want to return to the question of antimatter storage, which in my mind is far more significant a problem even than antimatter production. But there's time for that next week, and as I said yesterday, interesting stories keep accumulating and deserve our attention. Planetary Ejecta and Trapped Microorganisms What Tetsuya Hara (Kyoto Sangyo University) and colleagues put forth in a recent paper are their calculations about the ejection of life-bearing rocks and water into space from events like the possible 'dinosaur killer' asteroid impact some 65 million years ago, which involved an asteroid 10 kilometers in diameter. It's a...

Disruptive Planets and their Consequences

by Paul Gilster | May 24, 2012 | Uncategorized | 12 Comments

One of the joys of writing a site like Centauri Dreams is that I can choose my own topics and devote as much or as little time as I want to each. The downside is that when I'm covering something in greater depth, as with the four articles on antimatter that ran in the last six days, I invariably fall behind on other interesting work. That means a couple of days of catch-up, which is what we'll now see, starting with some thoughts on a possible planet beyond Neptune, a full-sized world as opposed to an ice dwarf like Pluto or Eris. This story is actually making the rounds right now, but it triggered thoughts on older exoplanet work I'll describe in a minute. It's inevitable that we call such a world Planet X, in my case because of my love for the wonderful Edgar Ulmer film The Man from Planet X (1951), in which a planet from the deeps wanders into the Solar System and all manner of trouble -- including the landing of an extraterrestrial on a foggy Scottish moor -- breaks out. Of...

Losing Our Cosmology

by Paul Gilster | May 23, 2012 | Deep Sky Astronomy & Telescopes | 26 Comments

Long-time Centauri Dreams readers know I love the idea of ‘deep time,’ an interest that cosmology provokes on a regular basis these days. Avi Loeb’s new work at Harvard tweaks these chords nicely as the theorist examines what we know and when we won’t be able to study it any longer. For an accelerating universe means that galaxies are moving outside our light horizon, to become forever unknown to us. Using tools like the Wilkinson Microwave Anisotropy Probe, we’ve been able to learn how density perturbations in the early universe, thought to have been caused by quantum fluctuations writ large by a period of cosmic inflation, emerged as the structures we see today. But are there limits to cosmological surveys? Start with that period of inflation after the Big Bang, which would have boosted the scale of things by more than 26 orders of magnitude, helping to account for the fact that the cosmic microwave background (CMB) appears so uniform in all directions. We can tease out the...

Toward a Beamed Core Drive

by Paul Gilster | May 22, 2012 | Antimatter | 14 Comments

If you didn't see this morning's spectacular launch of the SpaceX Falcon 9, be sure to check out the video (and it would be a good day to follow @elonmusk on Twitter, too). As we open the era of private launches to resupply the International Space Station, it's humbling to contrast how exhilarating this morning feels with the great distances we have to traverse before missions to another star become a serious possibility. We've been talking the last few days about the promise of antimatter, but while the potential for liberating massive amounts of energy is undeniable, the problems of achieving antimatter propulsion are huge. So we have to make a lot of leaps when speculating about what might happen. But let's assume just for the sake of argument that the problem analyzed yesterday -- how to produce antimatter in quantity -- is solved. What kind of antimatter engine would we build? If everything else were optimum, we'd surely try to master a beamed core drive, the pure product of the...

Antimatter: The Production Problem

by Paul Gilster | May 21, 2012 | Antimatter | 22 Comments

Antimatter is so tantalizing a prospect for propulsion that every time a new slant on using it appears, I try to figure out its implications for long-haul missions. But the news, however interesting, is inevitably balanced by the reality of production problems. There's no question that antimatter is potent stuff, with the potential for dealing out a thousand times the energy of a nuclear fission reaction. Use hydrogen as a working fluid heated up by antimatter and 10 milligrams of antimatter can give you the kick of 120 tonnes of conventional rocket fuel. If we could get the cost down to $10 million per milligram, antimatter propulsion would be less expensive than nuclear fission methods, depending on the efficiency of the design. But how to reduce the cost? Current estimates show that producing antimatter in today's accelerator laboratories runs the total up to $100 trillion per gram. But when I was researching my Centauri Dreams book, I spent some time going through the collection...

100 Year Starship Organization Launches

by Paul Gilster | May 18, 2012 | Culture and Society | 16 Comments

Today was to have been devoted to antimatter, continuing the discussion not only of how to produce the stuff on Earth or harvest it in nearby space, but how to create the kind of propulsion system that could tap its enormous energies. But the Dorothy Jemison Foundation for Excellence released its first public announcement about the 100 Year Starship yesterday, and I want to go right to that story given the interest that grew out of last year's starship symposium in Orlando. I'll get back to antimatter, then, and particularly the provocative work of Ronan Keane and Wei-Ming Zhang on magnetic nozzles for propulsion systems, on Monday. For today, though, let's talk about pushing out into the galaxy. The Tau Zero Foundation has a particular interest in the 100 Year Starship organization because our friends at Icarus Interstellar, who are re-thinking the 1970s Project Daedalus design, were partners in the winning proposal, which was called "An Inclusive, Audacious Journey Transforms Life...

Antimatter: Finding the Fuel

by Paul Gilster | May 17, 2012 | Antimatter | 30 Comments

In Stephen Baxter’s wonderful novel Ark (Roc, 2010), a team of scientists works desperately to come up with an interstellar spacecraft while epic floods threaten the Earth. The backdrop gives Baxter the chance to work through many of our current ideas about propulsion, from starships riding a wave of nuclear explosions (Orion) to antimatter possibilities and on into Alcubierre warp drive territory. I won’t give away the solution, but will say that it partly involves antimatter used in an unorthodox way, and because Baxter’s is a near-term Earth, there simply isn’t enough antimatter to go around. That means getting to Jupiter first to harvest it. Antimatter in space is an idea that James Bickford (Draper Laboratory) analyzed in a Phase II study for NASA’s Institute for Advanced Concepts, for he had realized that high-energy galactic cosmic rays interacting with the interstellar medium (and also with the upper atmospheres of planets in the Solar System) produce antimatter. In fact,...

Changing the Risk Paradigm

by Paul Gilster | May 16, 2012 | Asteroid and Comet Deflection | 17 Comments

As we continue to think about the implications of Planetary Resources and its plans for asteroid mining, I was interested to see exoplanet hunter Sara Seager (MIT) make a rousing case for the company's ideas and for commercial space ventures in general. Seager, who works with Planetary Resources as a science advisor, tells The Atlantic's Ross Andersen in a May 14 interview that one reason for optimism is the progress we're making with robotics. Mining operations currently being managed beneath the seas are being handled by robotics. Couple that with our ability to get to and orbit an asteroid as well as to scoop up surface materials and you have all the ingredients for a workable mining operation in a low-gravity environment. Seager explains that asteroids are attractive mining targets because unlike fully formed planets like the Earth, their heavier elements have not largely sunk inside through planetary differentiation in the early days of the planet's existence. Asteroids are...

A Near-Term Enterprise?

by Paul Gilster | May 15, 2012 | Missions | 28 Comments

It's too bad we don't already have a workable Enterprise, that vast near-term rendition of the Star Trek vehicle that a systems engineer named 'Dan' has been talking about on BuildTheEnterprise.org (a site which has been so heavily trafficked in the last 48 hours that it has proven almost inaccessible). What Dan has in mind is the design, down to the smallest level of detail, of a ship powered by three ion propulsion engines that tap on-board nuclear reactors to remain operational. It may not be an antimatter-powered Enterprise, but it's a faithful simulacrum, reflecting its creator's long-lasting interest in the ship that William Shatner once commanded. Dan thinks the new Enterprise could get us to Mars in 90 days, but getting nuclear reactors into low Earth orbit in the first place will be a challenge not only technically but politically, and shielding the crew will also involve a serious amount of mass that has to get lifted. One of the fascinations of this highly detailed site is...

Remembering Dandridge Cole

by Paul Gilster | May 14, 2012 | Culture and Society | 8 Comments

I've been thinking all weekend about Dandridge Cole, the aerospace engineer and futurist whose death at age 44 deprived interstellar studies of one of its most insightful advocates. Cole died in 1965, just five years before a deadline he himself set (in 1953!) for a manned landing on the Moon. But then, the former paratrooper from Ohio thought a lot about the future and the need for a kind of 'future studies' that would look at current technological trends and project going forward just as conventional historical studies reconstruct what happened to us in centuries past. The heart attack that struck Cole down in his office at General Electric's Space Technology Center in Valley Forge, PA deprived us of much, but we do have the substantial legacy of a number of articles and monographs, along with three books, among which Islands in Space: The Challenge of the Planetoids, written with Donald Cox (Chilton Books, 1964) may stand out as the most influential. Andreas Hein, who is heading...

Pushing Beyond Pluto

by Paul Gilster | May 11, 2012 | Missions | 15 Comments

What would you do if you had a spacecraft pushing toward the edge of the Solar System with nothing much to do? The answer is to assign it an extended mission, as we found out with the two Voyagers and their continuing data return that is helping us understand the boundaries of the heliosphere. In the case of New Horizons, NASA's probe to Pluto/Charon, two extended missions may be involved after Pluto, the first being a flyby of one or more Kuiper Belt targets, the second being a further look at what is actually going on where the solar wind meets the interstellar medium. Alan Stern, principal investigator for New Horizons, comments on the possibility in his latest report on the mission, noting that a second extended mission isn't out of the question, and adding that New Horizons won't make it as far as the Voyagers before it runs out of power. But 90 to 100 AU seems a possibility, which would provide a useful supplement to Voyager data. Remember that New Horizons carries two...

KOI-872: Timing is Everything

by Paul Gilster | May 10, 2012 | Exoplanetary Science | 9 Comments

It's no surprise that the techniques we're using to look for moons around exoplanets should start turning up new planets on their own. We're still looking for that first exomoon, but a team of researchers working with the Hunt for Exomoons with Kepler (HEK) project has found transit variations that have revealed a second planet around a star already known to have one transiting planet. The star is the intriguing KOI-872 (KOI stands for Kepler Object of Interest), the data on which were recently released by the Kepler team and analyzed swiftly by HEK. Kepler's transit methods examine the change in starlight when an exoplanet passes in front of the star being observed. This lightcurve, however, can tell more than a single tale. David Kipping (Harvard-Smithsonian Center for Astrophysics) is head of HEK and second author of the paper on the new work, which was published online today in the journal Science: "For a planet following a strictly Keplerian orbit around its host star, the...

Space Exploration: A Closing Window?

by Paul Gilster | May 9, 2012 | Culture and Society | 111 Comments

Our expectations determine so much of what we see, which is one of the great lessons of Michael Michaud's sweeping study of our attitudes toward extraterrestrial intelligence in Contact with Alien Civilizations (Springer, 2006). But extraterrestrials aside, I've also been musing over how our attitudes affect our perceptions in relation to something closer to home, the human space program. Recently I was reminded of Richard Gott's views on the space program and the Copernican Principle, which suggest that just as our location in the universe is not likely to be special, neither is our location in time. My expectation, for example, is that whether it takes one or many centuries, we will eventually have expanded far enough into the Solar System to make the technological transition to interstellar missions. But Gott (Princeton University) has been arguing since 2007 that there is simply no assurance of continued growth. In fact, his work indicates we are as likely to be experiencing the...

Jupiter Icy Moons Explorer

by Paul Gilster | May 8, 2012 | Outer Solar System | 17 Comments

Mars has always been a tempting destination because of the possibility of life. Thus the fascination of Schiaparelli's 'canals,' and Percival Lowell's fixation on chimerical lines in the sand. But look what's happened to the question of life elsewhere in the Solar System. We've gone from invaders from Mars and a possibly tropical Venus -- wonderful venues for early science fiction -- to a vastly expanded arena where, if we don't expect to find creatures even vaguely like ourselves, we still might encounter bacterial life in the most extreme environments. Astrobiology will push exploration. This is not to say that objects in deep space aren't worth studying in their own right, possible life or not, but merely to acknowledge that if we find life on another world, it deepens our view of the cosmos and fuels the exploratory imperative. A 'second genesis' off the Earth, once confirmed, would heighten interest in other targets where microbial life might take hold, from the cloud tops of...

Planetary Annihilation around White Dwarfs

by Paul Gilster | May 7, 2012 | Deep Sky Astronomy & Telescopes | 13 Comments

Can we tell something about the planets around another star by examining that star's atmosphere? A new study out of the University of Warwick makes a strong case for the method in the study of white dwarfs, following up on a landmark 2007 paper by Benjamin Zuckerman (UCLA) that looked at pollution in white dwarf photospheres. 'Pollution' as in metals that shouldn't be there, which suggests an accretion disk of material feeding the star, which itself would have collapsed from a red giant stage and is perhaps now absorbing planetary material around it. What we would expect to find in the atmosphere of a white dwarf is little more than hydrogen and helium -- heavy elements should quickly sink to the core and not be observable. But white dwarfs with metal-contamination in their atmospheres have been observed for almost a century now. Let me Boris Gänsicke and colleagues on this, from the paper on the University of Warwick work (internal references deleted for brevity): ...the rapidly...

Rogue Stars Leaving the Galaxy

by Paul Gilster | May 4, 2012 | Deep Sky Astronomy & Telescopes | 8 Comments

Having just re-read Arthur C. Clarke's The City and the Stars for the first time in a couple of decades, I've been preoccupied by the idea of 'deep time,' and astronomical events that play out over billions of years. The fictional trick, of course, is to pair human observation with events that take aeons to unfold. In Clarke's novel, the city of Diaspar is a place that is almost outside of time, a self-contained and beautiful place whose very inwardness ultimately becomes stultifying. But the vision of this glowing jewel of a city surviving amidst the dunes of an ancient Earth is one of those science fiction images that stick with you over a lifetime of reading. New work out of Vanderbilt University now suggests other deep time images, but they're likely to be more fantasy than science fiction. Imagine a star moving fast enough to escape the galaxy, living out its life on a long trajectory that will take it into intergalactic space. Kelly Holley-Bockelmann and Lauren Palladino think...

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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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