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Swansong Earth: Refuges for Life

by Paul Gilster | Oct 31, 2012 | Astrobiology and SETI | 17 Comments

As we begin to identify planets in the habitable zone of their stars, the larger issue becomes what fraction of stars have such planets. This is eta-Earth (?Earth), the percentage of Sun-like stars with Earth-like planets in the habitable zone, a figure we can gradually home in on as statistical surveys like Kepler continue to churn. Right now the estimate depends on whom you talk to, with figures ranging from 1.4-2.7% (Catanzarite & Shao, 2011) to 42% for red dwarf stars (Bonfils et al., 2011). One thing I haven’t seen discussed much is the question of when planets cease being habitable, including what we can call the phases of habitability on a given world. Jack T. O'Malley-James (University of St Andrews, UK) and colleagues have gone to work on the question in a new paper slated for publication in the International Journal of Astrobiology. The researchers note that life emerged on Earth 3.8 billion years ago and perhaps somewhat earlier. The key point is that unicellular organisms...

Asteroid Deflection: The Paintball Solution

by Paul Gilster | Oct 30, 2012 | Asteroid and Comet Deflection | 42 Comments

Planetary Resources has us thinking about mining the asteroids to extract useful materials, but learning more about these objects will benefit us in all kinds of ways. Not only do asteroids offer up clues about the early Solar System, but getting to understand their composition and structure will be a key element in any future plans to change an asteroid trajectory. The topic comes to mind periodically as various asteroids make close approaches, and right now I'm looking at asteroid 2012 DA14, which will close to within 22,000 kilometers this coming February. 2012 DA14 is a small asteroid, discovered in early 2012 at the Observatorio Astronómico de La Sagra in Spain, and it is not an impact threat for us next year, although prudence dictates keeping an eye on it for future orbits -- the object is recently enough discovered that we'll need to study it longer to get a better read on future encounters. I see that the University of Central Florida is organizing a viewing party in...

Opening Minds to the Stars

by Paul Gilster | Oct 29, 2012 | Culture and Society | 8 Comments

When it comes to experiencing the night sky, there are times when mathematics fades away and poetry comes to the fore. Witness these lines from John Milton's Paradise Lost: A broad and ample road, whose dust is gold, And pavement stars, as stars to thee appear Seen in the galaxy, that milky way Which nightly as a circling zone thou seest Powder'd with stars. The lines bring back a crisp fall night in the Adirondacks when my wife, my daughter and I were crossing Lake George in a small boat. I've seen the Milky Way from many places but never has it seemed so striking as that night, perfectly framed by the surrounding hills, and Milton's word 'powder'd' has the scene exactly right, for the stars seemed like a fine dust interspersed with jewels. The closest photo I've seen that captures a scene like this is a spectacular image taken over the snowy cliffs of Creux du Van near Neuchâtel, Switzerland that I found in a new book from the Smithsonian called Universe: The Definitive...

SETI: Rummaging in the Data

by Paul Gilster | Oct 26, 2012 | Astrobiology and SETI | 60 Comments

Astronomy is moving at a clip that sees more data accumulated than can possibly be examined at the time they're collected. We're creating vast storehouses of information that can be approached from various angles of study. Now ponder how we might use these data for purposes beyond what they were collected for. In a new paper submitted to the Astronomical Journal, Ermanno Borra (Université Laval, Québec) looks at how standard astronomical spectra -- including those already taken -- can be used as part of SETI, the Search for Extraterrestrial Intelligence. Here's the idea: Suppose somewhere out there a civilization decides to reveal its existence to the rest of the galaxy. These extraterrestrials reason from their own experience of science that an advanced civilization will study the sky and take spectra of astronomical objects. These spectra become the medium upon which the senders impose their signal. At our end, spectroscopic surveys of vast numbers of stars allow us...

Wanderers Between the Galaxies

by Paul Gilster | Oct 25, 2012 | Deep Sky Astronomy & Telescopes | 23 Comments

The idea of planets outside their normal settings is unsettling. It implies that beyond the stars all around us there may be worlds without suns, dark planets presumably pushed there by gravitational instabilities in their home systems. We've looked at such 'nomad' worlds before, noting that ice overlaying a frozen ocean might trap enough geothermal heat to create life-sustaining conditions. Estimates on how many such planets might exist vary widely, but in one recent paper Louis Strigari (Stanford University) has calculated that 105 objects larger than Pluto may exist for every main sequence star (see Island-Hopping to the Stars for more on Strigari's work on free-floating planets). Survey missions like Gaia may help us find some of these. If a wandering world between the stars is a chilling prospect, what about stars that wander between the galaxies? We have plenty of evidence for their existence. Strip away the emissions from our own Solar System and the Milky Way itself and what...

On Missions and Nearby Stars

by Paul Gilster | Oct 24, 2012 | Missions | 38 Comments

Sara Seager's thoughts on who might join a crew bound for Alpha Centauri have had resonance, as witness Dennis Overbye's story Discovery Rekindles Wish for a Journey to the Stars in the New York Times. Overbye, a touchstone in science journalism, has probably been pondering the issue because of Seager's response to his question about Centauri B b. The MIT astronomer laid it out starkly: "I think we should drop everything and send a probe there." Seager is well aware of the issues involved and knows what a project it would be to drive a lightsail -- or some other kind of spacecraft -- up to ten percent of the speed of light. But she has us all thinking about the kind of people who would go on future manned missions (and whether they might wind up changing their minds). Overbye can look back at his high school yearbook, where he finds "Ambition: To go to the stars." These days he's thinking more about what would happen if he really did: Perhaps it is a sign of my age that I think more...

Deck Hands for a Four Decade Journey

by Paul Gilster | Oct 23, 2012 | Missions | 63 Comments

?If you were offered a chance to make an interstellar journey, would you take it? How about a garden-variety trip to low-Earth orbit? I’m often asked questions like this when I make presentations to the public, and I have no hesitation in saying no. Though I’m no longer doing any flight instructing, I used to love flying airplanes, but getting into a rocket and being propelled anywhere is not for me. To each his own: I’m fascinated with deep space and hope many humans go there, and you can count on me to write about their missions and robotic ones as well while keeping my office right here on Earth. The point is, the percentage of people who actually go out and take the incredible journeys and fly the dangerous missions is vanishingly low. But throughout history, there have always been a few intrepid souls who were willing to get into the canoes or the caravels or the biplanes and open up new territories and technologies. Thank God we have the Neil Armstrongs and Sergei Krikalyovs of...

Centauri B: Targets and Possibilities

by Paul Gilster | Oct 19, 2012 | Missions | 60 Comments

Voyager 1, now 17 light hours from Earth, continues to be my touchstone when asked about getting to Alpha Centauri -- and in the last few days, I've been asked that question a lot. At 17.1 kilometers per second, Voyager 1 would need 74,000 years to reach the blistering orb we now believe to be orbiting Centauri B. Voyager 1 is not the fastest thing we've ever launched -- New Horizons at one point in its mission was moving with greater velocity, though no longer, and the Helios II Solar probe, no longer functional, reaches about 70 kilometers per second at perihelion. But Voyager 1 will be our first craft to reach interstellar space, and it continues to be a measure of how frustratingly far even the nearest stars happen to be. Cautionary notes are needed when a sudden burst of enthusiasm comes to these subjects, as it seems to have done with the discovery of Centauri B b. What we need to avoid, if we've got our eyes on long-term prospects and a sustained effort that may take centuries...

Reflections on Centauri B b

by Paul Gilster | Oct 18, 2012 | Uncategorized | 28 Comments

When planet-hunter Greg Laughlin (UC-Santa Cruz) took his turn at the recent press conference announcing the Alpha Centauri B findings, he used the occasion to make a unique visual comparison. One image showed the planet Saturn over the limb of the Moon, as shown immediately below in a 1997 photo from Krzysztof Z. Stanek. Think of this as the Galilean baseline, for when Galileo went to work on the heavens with his first telescope, the Moon was visually close at hand and Saturn a mysterious, blurry object with apparent side-lobes. Laughlin contrasted that with the image I ran yesterday, showing the Alpha Centauri stars as viewed from Saturn, a spectacular vista including the planet and the tantalizing stellar neighbors beyond. Four hundred years after Galileo, we thus define what we can do -- a probe of Saturn -- and we have the image of a much more distant destination we'd like to know a lot more about. The findings of the Geneva team take us a giant step in that direction, revealing...

Alpha Centauri and the New Astronomy

by Paul Gilster | Oct 16, 2012 | Exoplanetary Science | 84 Comments

For much longer than the nine years Centauri Dreams has been in existence, I've been waiting for the announcement of a planetary discovery around Centauri B. And I'm delighted to turn the first announcement on this site over to Lee Billings, one of the most gifted science writers of our time (and author of a highly regarded piece on the Centauri stars called The Long Shot). Lee puts the find into the broader context of exoplanet research as we turn our gaze to the nearest stars, those that would be the first targets of any future interstellar probes. On Thursday I'll follow up with specifics, digging into the discovery paper with more on the planet itself and the reasons why Centauri B was a better target than nearby Centauri A. I'll also be offering my own take on the significance of the find, which I think is considerable. by Lee Billings For much of the past century, astronomy has been consumed by a quest to gaze ever deeper out in space and time, in pursuit of the universe's...

Circumbinary Planet in a Four Star System

by Paul Gilster | Oct 16, 2012 | Exoplanetary Science | 2 Comments

Continuing with what promises to be a seriously interesting week in exoplanet studies, I want to home in this morning on PH1, a planet that reminds us how much the public has become involved in ongoing science thanks to the widespread distribution of computer power. As presented at the annual meeting of the Division for Planetary Sciences of the American Astronomical Society in Reno (NV), the finding pairs volunteers working with the crowdsourced Planet Hunters project with an international team of professional astronomers led by Yale University's Meg Schwamb. The volunteers -- Kian Jek of San Francisco, California, and Robert Gagliano of Cottonwood, Arizona -- were the first to spot the telltale lightcurve of a transit, which was then confirmed by astronomers using the Keck instruments at Mauna Kea (Hawaii). What the investigation uncovered was a gas giant about 6.2 times the radius of the Earth, putting it into Neptune-territory. But what really flags the attention is the fact that...

Exoplanet Missions Beyond Kepler

by Paul Gilster | Oct 15, 2012 | Exoplanetary Science | 18 Comments

Because it's going to be an interesting week for exoplanet studies (for reasons I'll talk about soon, though not today), I'll lead off with some thoughts on eta-Earth, defined as the fraction of Sun-like stars with a planet like Earth orbiting them. We have a lot to learn about the frequency of terrestrial worlds, and as Philip Horzempa points out in a recent article for The Space Review, the image that's gradually emerging is of fewer 'Earths' than Carl Sagan once estimated when he said in the 1980s that half of all stars could have a planet like our own. Image: Artists' concepts of small exoplanets compared to our own planets Mars and Earth. As Kepler continues to hunt, how can we move beyond its findings to learn more about terrestrial planets around much closer stars? Credit: NASA/JPL-Caltech With Kepler's continuing datastream and improving ground-based instrumentation, we're learning more about planet distribution, but Horzempa notes that even now, estimates of Earth analogs...

The Institute for Interstellar Studies

by Paul Gilster | Oct 12, 2012 | Uncategorized | 9 Comments

by Kelvin F. Long I recently asked Kelvin Long to write an introduction to the Institute for Interstellar Studies he has created, and he was kind enough to send along a useful overview, along with a backgrounder on his own work: "Kelvin Long is an aerospace engineer and physicist. He is chief editor of the Journal of the British Interplanetary Society, author of the book Deep Space Propulsion: A Roadmap to Interstellar Flight, and was the key founder behind the starship design study Project Icarus. Since 2007 he has worked to catalyse the interstellar community through the organization of lectures, symposia, publications and design studies. He is currently the Executive Director for the Institute for Interstellar Studies, founded in August 2012." Here Kelvin describes the new Institute and relates its mission to prior work in deep space technologies. The subject of Interstellar Studies derives its name from a set of special red cover issues of the Journal of the British...

Dyson Sphere Hunt Using Kepler Data

by Paul Gilster | Oct 11, 2012 | Astrobiology and SETI | 57 Comments

The idea of the multiverse -- an infinite number of universes co-existing with our own -- has a philosophical and mathematical appeal, at least if you're a follower of string theory. Indeed, there are those who would argue there could be as many as 10500 universes, each with its own particular characteristics, most probably inimical to the development of life. But I have to say that I'm far more interested in the universe that is demonstrably here, our own, and thus the news that Geoff Marcy has received a grant to look for Dyson spheres catches my eye more than news of a similar grant to physicist Raphael Bousso to probe multiverse theory. Not that I have anything against Dr. Bousso (UC-Berkeley) and his work, and if he eventually does find a way to make predictions of multiverse theory that can be tested, I'm all for it. But I think the new grants, given to the researchers in a series called New Frontiers in Astronomy & Cosmology International Grants (funded through the UK's...

Musings on Solitude and Contact

by Paul Gilster | Oct 10, 2012 | Astrobiology and SETI | 22 Comments

Back in 2007, science writer Lee Billings put together a panel for Seed Media Group on "The Future of the Vision for Space Exploration." The session took place at the Rayburn House Office Building on Capitol Hill, and I remember flying to Washington with a bad head cold to moderate the event. Miraculously, my cold abated and I enjoyed the company of Louis Friedman (The Planetary Society), Steven Squyres (of Mars rover fame), Edward Belbruno (Princeton University) and interstellar guru Greg Matloff (CUNY). But I particularly remember conversations with Lee. I can't say I was surprised to see him go on to emerge as one of the most gifted science writers now working. Not long afterwards, Lee wrote an essay called The Long Shot for SEED Magazine that took him into the thick of the exoplanet hunt, from which this fine paragraph about the nearest stars and why they have such a hold on us: Alpha Centauri is today what the Moon and Mars were to prior generations—something almost...

Growing Into an Interstellar Civilization

by Paul Gilster | Oct 9, 2012 | Culture and Society | 92 Comments

While I've often opined in these pages that a Solar System-wide infrastructure must emerge before we can contemplate interstellar flight, the obvious question is how we get there. Stephen Ashworth (Oxford, UK), who writes the insightful Astronautical Evolution blog, recently tackled the subject with such vigor that I asked him for permission to run his essay verbatim, especially since it grew out of a discussion right here on Centauri Dreams. If you're trying to do something spectacular -- like growing a global civilization into an interplanetary one and boosting wealth into the realms needed to push to the stars -- how would you go about it? Ashworth's vision for the 'ten-billion-times growth factor' makes the needed transformation. Is it a logical extrapolation or does it push too far? A lively debate should grow out of this one. As a lifelong jazz buff, I can't resist adding that Stephen is to be heard on tenor sax playing jazz standards at the Monday evening jam sessions at...

Titan Exploration Options

by Paul Gilster | Oct 8, 2012 | Outer Solar System | 12 Comments

One of the challenges of running a site like Centauri Dreams is that deep space news accumulates so swiftly that it's easy to focus on one issue while another timely story slips away. I don't want to get too far past the European Planetary Science Congress, which ended in Madrid on September 28, without mentioning the interesting discussion of Titan that took place there. A new proposal for landing on the moon and sampling Ligeia Mare, its largest lake, was put forward to join previous Titan exploration proposals, all of them challenging yet doable. Titan Lake In-situ Sampling Propelled Explorer (TALISE) is the brainchild of SENER, a private engineering and technology group that has provided components and subsystems for a wide variety of space missions. The idea is to land a probe in the middle of Ligeia Mare, near Titan's north pole, and embark on a six- to twelve-month cruise to the coast, gathering data all the way. TALISE team member Igone Urdampilleta explains what makes TALISE...

Colors of a Living World

by Paul Gilster | Oct 5, 2012 | Exoplanetary Science | 13 Comments

Gliese 581d seems more and more to be considered a habitable zone planet, as Siddharth Hegde (Max Planck Institute for Astronomy) and Lisa Kaltenegger (Harvard-Smithsonian Center for Astrophysics) describe it in a new paper. They're homing in on how to characterize a rocky exoplanet and point to HD 85512b and Gliese 667Cc as well as Gl581d as examples, but they also assume that we'll be seeing more and more habitable zone worlds as the Kepler mission continues its work, so how we learn more about these planets becomes a big issue. In the absence of missions like Terrestrial Planet Finder or ESA's Darwin, which would allow us to analyze an exoplanetary atmosphere for biomarkers, what else can we do to find the places where life exists? Hegde and Kaltenegger look hard at a planet's color to find the answer. Specifically, they're interested in what's known as a color-color diagram, which takes advantage of the fact that an object can be observed at a variety of wavelengths, with a...

Cometary Dust Around ??Pictoris

by Paul Gilster | Oct 4, 2012 | Exoplanetary Science | 4 Comments

New findings from the Herschel space observatory demonstrate how effective the infrared telescope can be at teasing out details of distant planetary systems. At issue is the system around Beta Pictoris, a young star (12 million years old) some 63 light years from the Earth. We’re looking at planetary system formation in progress here, with a single gas giant planet and a dusty debris disk that may be the forerunner of a disk much like our own Edgeworth/Kuiper Belt, the collection of icy bodies that orbits outside the orbit of Neptune. Ben de Vries (KU Leuven) is lead author of the paper on the new Herschel data, which examines the composition of dust in the outer regions of the Beta Pictoris disk. The study, reported today in Nature, presents a photometric and spectral analysis of dust particles produced when planetesimals in this region collide. The key player here is olivine, a mineral associated with protoplanetary disk material around newborn stars. The olivine found around Beta...

Remembering “Men Into Space”

by Paul Gilster | Oct 3, 2012 | Culture and Society | 24 Comments

Yesterday's discussion about Man Will Conquer Space Soon!, the landmark series in Collier's that so elegantly defined the 1950s view of space travel, has me in a retrospective mood. The Collier's series was highly visible, and those old enough to have seen it tend to remember its concepts whether or not they're in an aerospace-related profession today. But a few years later a TV show called "Men Into Space" turned up on CBS, fighting for audience share and generally out-publicised by the network's "Twilight Zone" offering. It would run only a single season and end in September of 1960, months before Yuri Gagarin's daring ride in a Vostok. But "Men Into Space" sticks with me for a reason. Its 38 episodes followed Col. Edward McCauley (played by William Lundigan) through a variety of space situations, using him as a viewpoint character while the astronauts he worked with dealt with breakthroughs and problems. In that sense there was a certain similarity to what would become the Mercury...

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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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