Paul Gilster | Centauri Dreams

Physicists Surveying the Future

by Paul Gilster | Nov 12, 2012 | Culture and Society | 57 Comments

Back in 1968. when I saw Stanley Kubrick’s 2001: A Space Odyssey on the gigantic curved screen at the Ambassador Theater in St. Louis, I thought that the timing was a bit optimistic. December of that year would see the first trip around the Moon, a startling and expansive moment, but even with Apollo in the air, I thought a human mission to the moons of Jupiter would take longer than 2001. 2025 seemed more like it. Now, of course, we see that 2025 is out of the question for manned missions, and the best attitude for space futurists is caution. It’s easy to see how tricky the future is to predict by looking at the past. If you extrapolated from the technology of the Hellenistic Greeks, you would have wound up with a space-going civilization somewhere around 1300, as Carl Sagan once speculated. Bumps happen along the way, civilizations topple, technologies are shelved. Even so, the allure of prognosis keeps us looking ahead, and the truly optimistic among us can easily go over the top....

Exomoons: A Direct Imaging Possibility

by Paul Gilster | Nov 9, 2012 | Exoplanetary Science, Uncategorized | 19 Comments

It's good to see that David Kipping's work on exomoons is back in the popular press in the form of A Harvest of New Moons, an article in The Economist. Based at the Harvard-Smithsonian Center for Astrophysics, Kipping's Hunt for Exomoons with Kepler (HEK) culls Kepler data and massages the information, looking for the tug of large moons on transiting exoplanets. The basic method will by now be familiar to Centauri Dreams readers: Dr Kipping's technique relies on the fact that moons do not simply revolve around their host planets; planets also revolve around their moons—or, rather, the two bodies both revolve around their common centre of mass. If a planet is large and its moon small the distinction is trivial. But if the planet is small and the moon is large, it is not. In the case of Earth and its moon, for example, the common centre lies only around 1,700km (1,100 miles) beneath the Earth's surface. Someone looking from afar at the movement of Earth would thus be able to...

Possible Habitable World in a Six-Planet System

by Paul Gilster | Nov 8, 2012 | Exoplanetary Science | 34 Comments

At 42 light years from Earth, the star HD 40307 is reasonably within the Sun’s neighborhood, so the news of a potentially habitable planet there catches the eye. HD 40307 is a K-class dwarf, one previously known to be orbited by three super-Earths -- with masses between the Earth and Neptune -- that are too close to the star to support liquid water on the surface. Now we have the discovery, announced in a new paper in Astronomy & Astrophysics, of three more super-Earth candidates found by digging into data from HARPS (the High Accuracy Radial Velocity Planet Searcher) and HIRES (the High Resolution Echelle Spectrograph). Mikko Tuomi (University of Hertfordshire) and team put a new software tool called HARPS-TERRA to work on the archival data that allowed them greater precision in filtering out false positives from stellar activity. Says Tuomi: "We pioneered new data analysis techniques including the use of the wavelength as a filter to reduce the influence of activity on the signal...

Re-Envisioning the Telescope

by Paul Gilster | Nov 6, 2012 | Deep Sky Astronomy & Telescopes | 14 Comments

An inventor named Tom Ditto has been casting a serious look at diffraction gratings as large primary collectors for telescopes, work that has been getting a bit of a buzz on the Internet. See, for example, An Old Idea Gives Telescopes a New Twist, and ponder how much the eponymous Dittoscope sounds like something out of a Tom Swift story. Nonetheless, an instrument based on a diffraction grating as its primary light-gathering source may prove useful in a variety of astronomical settings, including the ability to produce extremely high quality spectroscopic information for radial velocity exoplanet searches. Diffraction happens when a small obstacle or opening causes a wave of light to interfere with itself, creating patterns that depend on the size of the diffracting object and the size of the wave. A diffraction grating, in this case a flat surface with a regular pattern of grooves, can be used to separate different wavelengths of light, which will interfere at different angles. The...

Vesta: A Protoplanet’s Mutable Surface

by Paul Gilster | Nov 5, 2012 | Deep Sky Astronomy & Telescopes | 8 Comments

I remember having a particularly strong 'sense of wonder' moment when reading Poul Anderson's "The Snows of Ganymede" when I was a kid. Anderson was good at this kind of thing, but really my reaction was not just to this story but to the whole notion of taking a distant astronomical object and placing people in it. A bright point in the telescope suddenly becomes a landscape and you feel your sense of scale - the sheer immensity of things - beginning to shift under your feet. These thoughts are triggered by the latest news from the Dawn mission about Vesta, and a UCLA news release commenting on the asteroid's steep topography, which often leads to landslides. Immediately I was thinking of stark drops and boulder-strewn regolith with no friendly blue/green Earth in the sky and wondering what it would be like to see Vesta in person. Thus dreams accumulate. Ray Bradbury found that attaching names to unknown places is a distinctively human enterprise, and one that when abandoned...

Astrobiology: The Necessity of Asteroids

by Paul Gilster | Nov 2, 2012 | Asteroid and Comet Deflection | 43 Comments

Let's talk this morning about the 'snow line,' the boundary in the Solar System beyond which volatiles like water ice remain cold enough to keep intact. Rebecca Martin (University of Colorado) and Mario Livio (Space Telescope Science Institute) have been running simulations using models of planet-forming disks around young stars. The idea: To calculate the location of the snow line in these disks as measured against the mass of the central star. Their hypothesis is that asteroid belts in other solar systems will be located at the snow line, with implications for life. Here's the thinking on this. We know that asteroids, in addition to creating impact threats that can trigger world-changing events, may also have had a crucial role delivering water and organic compounds to the early Earth. Occasional asteroid impacts, says the theory of punctuated equilibrium, may have accelerated biological evolution, forcing species to adapt to rapidly changing conditions. And there are still other...

G-Class Outliers: Musings on Intelligent Life

by Paul Gilster | Nov 1, 2012 | Astrobiology and SETI | 55 Comments

Because I had my eyes dilated yesterday afternoon en route to learning whether I needed new reading glasses (I do), I found myself with blurry vision and, in the absence of the ability to read, plenty of time to think. Yesterday’s post examined a paper by a team led by Jack T. O’Malley-James (University of St Andrews, UK), addressing the question of how our planet will age, and specifically, how life will hang on at the single-cell level into the remote future. It’s interesting stuff because of its implications for what we may find around other stars and I pondered it all evening. Have a look at one of the figures from the O’Malley-James paper, which shows the stages a habitable Earth-like planet (ELP) will pass through as it ages around main sequence stars. I also clip the caption directly from the paper. Image: Time windows for complex and microbial life on Earth analogue planets orbiting Sun-like stars (F(7), G and K(1) stars) during their main sequence lifetimes. Assuming that...

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...

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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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