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A Solar Sail Manifesto

by Paul Gilster | Apr 30, 2009 | Sail Concepts | 23 Comments

I was startled to see the Breakthrough Propulsion Physics project make the pages of The Atlantic in its current issue. Novelist Thomas Mallon, in an essay largely devoted to solar sailing and The Planetary Society's efforts in that direction, gives vent to some of the frustration, if not exasperation, many of us feel as we see basic research losing out to short-term missions whose purpose is by no means clear. "American politicians now mostly avoid the old conditional trope 'If we can put a man on the moon' — because we can't, not anymore," writes Mallon, who goes on to lament the passage of the BPP project and, five years later, NASA's Institute for Advanced Concepts. Questioning Why We Explore In Mallon's view, the sense of exploration is itself under attack: Even the most spectacular unmanned successes of the American space program — from the Voyager probes of the '70s to the Galileo and Cassini missions of the '90s — seem to belong to a fading worldview. A...

Renewed Challenge to the Dinosaur Killer

by Paul Gilster | Apr 29, 2009 | Asteroid and Comet Deflection | 10 Comments

Some scientific hypotheses seem too perfect to be anything but true. Long before we understood the processes behind plate tectonics, the natural fit between the coasts of Africa and South America made the notion of their original linkage seem obvious. Although dismissed in many quarters as mere coincidence, the piecing together of earlier continents would follow. The hypothesis of continental movement, whatever the cause, was almost too obvious not to be true. But does science really work so neatly? Writing about his work on the evident 'dinosaur killer' event at the Cretaceous/Tertiary boundary, Walter Alvarez once said: "Much of the work we do as scientists involves filling in the details about matters that are basically understood already, or applying standard techniques to new specific cases. But occasionally there is a question that offers an opportunity for a really major discovery." And the K/T impact seemed, like the continental coastlines, to be an obvious fit, a...

Eccentric Orbits and Bold Predictions

by Paul Gilster | Apr 28, 2009 | Culture and Society | 18 Comments

The 100th edition of the Carnival of Space is now up at the One-Minute Astronomer site, where I learned of the existence of Christopher Crockett's Innumerable Worlds blog. Christopher's story on two gas giants around subgiant stars is well worth reading. He's a UCLA graduate student now working at Lowell Observatory who offers a good deal of background material in his posts, as in this comment on the new planets' unusually eccentric orbits: How planets end up on such crazy orbits is a matter that is currently being researched. These two worlds aren't alone; many of the new worlds we're finding sit on highly eccentric orbits. The leading hypothesis is that interactions between closely spaced planets might affect their orbits. If two planets get too close, the lighter one can get ejected from the planetary system entirely while the remaining, more massive, world is left behind on a very elliptical orbit. This is the same principle we use to slingshot probes out into deep space by...

Pushing Past Redshift Eight

by Paul Gilster | Apr 28, 2009 | Deep Sky Astronomy & Telescopes | 10 Comments

No one has ever seen an object further away than the one at the center of the image below. It's a gamma-ray burst known as GRB 090423, spotted by the Swift satellite on April 23rd and quickly observed by the Gemini Observatory and United Kingdom Infrared Telescope, both on Mauna Kea (Hawaii). The source is visible at longer wavelengths but disappears at the 1 micron level, all of which corresponds to a distance of about thirteen billion light years. Image: The fading infrared afterglow of GRB 090423 appears in the center of this false-color image taken with the Gemini North Telescope in Hawaii. The burst is the farthest cosmic explosion yet seen. Credit: Gemini Observatory/NSF/AURA, D. Fox and A. Cucchiara (Penn State Univ.) and E. Berger (Harvard Univ.) Spectacular, no? Numerous telescopes around the planet went on to observe the GRB's afterglow, allowing the infrared light's spectrum to confirm the highest redshift ever measured: z = 8.2. The object in question was probably a...

Getting Closer to an Exomoon Detection

by Paul Gilster | Apr 27, 2009 | Astrobiology and SETI, Exoplanetary Science | 20 Comments

Finding moons around extrasolar planets is an invigorating quest. After all, at least three moons around gas giants right here in our own system -- Europa, Enceladus and Titan -- are considered of high astrobiological interest. What about gas giants in the habitable zone of some distant star? The image below shows what a moon of such a planet one might look like, as imagined by astronomer Dan Durda (Southwest Research Institute). Could such worlds be? As we learn more, bear in mind that the hunt for 'exomoons' has already begun. The CoRoT spacecraft is searching for transit timing variation signals (TTV) -- variations in the time it takes a planet to transit its star -- as described by Sartoretti and Schneider in a 1999 paper. David Kipping (University College London) has been developing a second method called transit duration variation (TDV), which works in conjunction with the first. The TDV signal is brought about by velocity changes as the planet/moon 'system' is observed over...

Upcoming Beamed Propulsion Conference

by Paul Gilster | Apr 24, 2009 | Sail Concepts | 3 Comments

A note from Eric Davis (Institute of Advanced Studies at Austin) fills me in on the details of the upcoming 6th International Symposium on Beamed Energy Propulsion, to be held in Scottsdale, AZ during the first week of November. Much of the program is of interest to interstellar studies, ranging from the basic science and technology of laser, microwave and particle beam propulsion to specifics relating the topic to beamed interstellar missions. The latter subject will always be associated with Robert Forward, whose studies of beaming technology and sails made us understand that reaching the stars was not necessarily impossible. Lasers were the key, as Forward learned through his work with Ted Maiman at Hughes Research Laboratory. Years later he recalled his 'eureka' moment: "I knew a lot about solar sails, and how, if you shine sunlight on them, the sunlight will push on the sail and make it go faster. Normal sunlight spreads out with distance, so after the solar sail has reached...

Asteroid Deflection by Tether

by Paul Gilster | Apr 23, 2009 | Asteroid and Comet Deflection | 4 Comments

Diverting incoming asteroids is a high priority item, and so is a mission to a nearby asteroid for a close-up study of its composition and a shakeout of operating technologies. Think about the movie Deep Impact. Nukes are used to break up an incoming object, in this case a comet, but the resultant deadly chunks are still headed toward Earth. The planet suffers one disastrous collision, but it turns out to be survivable due to quick thinking and the willingness of a spacecraft crew to sacrifice themselves by blowing up the remaining impactor. Get past the Hollywood cliffhanger elements and Deep Impact had its moments (in any case, I'll sign off on any movie with Robert Duvall in it). The use of nuclear weapons in the movie does raise a legitimate question -- do we know enough about what might hit us to predict what would happen if we did try to destroy it this way? That's one reason we need early missions to study Earth-crossing asteroids, and it's also a reminder that keeping our...

Ubiquitous Brown Dwarfs: A Dark Matter Solution?

by Paul Gilster | Apr 22, 2009 | Deep Sky Astronomy & Telescopes | 29 Comments

Three brown dwarfs with masses that push up against the boundary between star and planet have been identified in IC 348, a star-forming region some 1000 light years from Earth in the direction of the constellation Perseus. The dwarfs do not appear to be gravitationally bound to a star although they are bound by the cluster, and they're useful as we try to broaden our understanding of the mass distribution in newly formed stellar populations. Andrew Burgess (Observatoire de Grenoble) has this to say about the find: "There has been some controversy about identifying young, low mass brown dwarfs in this region. An object of a similar mass was discovered in 2002, but some groups have argued that it is an older, cooler brown dwarf in the foreground coinciding with the line of sight. The fact that we have detected three candidate low-mass dwarfs towards IC 348 supports the finding that these really are very young objects." Image: IC 348, the star-forming region where the brown dwarfs were...

Water World Around Gliese 581?

by Paul Gilster | Apr 21, 2009 | Exoplanetary Science | 25 Comments

Gliese 581, the star that teased us a few years back with reports of a 'super-Earth' planet in the habitable zone, is back in the news. Michel Mayor's Geneva team has located a fourth planet in the system, Gliese 581 e, which weighs in at a mere 1.9 Earth masses, making it the least massive exoplanet ever detected. Orbiting its primary in 3.15 days, the newly found world is too close to the star to be in the habitable zone, but the other shoe that drops here is that Gl 581 d may itself be. Image: By refining the orbit of the planet Gliese 581 d, first discovered in 2007, a team of astronomers has shown that it lies well within the habitable zone, where liquid water oceans could exist. This diagram shows the distances of the planets in the Solar System (upper row) and in the Gliese 581 system (lower row), from their respective stars (left). The habitable zone is indicated as the blue area, showing that Gliese 581 d is located inside the habitable zone around its low-mass red star....

Wolf 940’s Brown Dwarf Companion

by Paul Gilster | Apr 20, 2009 | Exoplanetary Science | 12 Comments

News about a nearby brown dwarf occupies us this morning, but first, a quick site update. The recent server problems did not, fortunately, result in the loss of any data, but I've had to make some temporary software changes to get Centauri Dreams back up. Expect more changes in coming weeks as I replace these fixes, so you may see things in transition for a time, but the server switchover is complete. One remaining problem is a snafu in image uploads that I hope to fix soon. Now, to brown dwarfs. Seeing them is tricky business. Too small to be stars (although they do fuse deuterium), too massive to be planets, they're hard to pick out in visible light and are generally detected at infrared wavelengths. Now a faint brown dwarf orbiting the nearby star Wolf 940 has been discovered. The primary is a red dwarf some 40 light years from Earth, orbited by its dim neighbor at a distance of some 440 AU. This may bring to mind our recent discussion of Lorenzo Iorio's work, which settled on a...

A Delay Like No Other

by Paul Gilster | Apr 20, 2009 | Culture and Society | 5 Comments

Postponements of major science projects are generally dismaying, but sometimes they become so grand they attain a kind of immortality. The latest multi-billion dollar delay boggles the mind: "Delays of this magnitude were once the stuff of science fiction," Scolese told reporters during a noon press conference Monday that actually started around 3:15 p.m. "But now, thanks to a number of long-overdue technological advances, this historic delay will stretch the very limits of what humankind can push back indefinitely." You won't want to miss The Onion's take as NASA Embarks On Epic Delay.

Server Problems Implode Weekend

by Paul Gilster | Apr 18, 2009 | Administrative | 5 Comments

And I thought I was going to more or less take the weekend off, maybe finishing up a second reading of Rare Earth and enjoying some of the delightful spring weather that has taken hold around here. So much for that. Server issues caused this site to be transferred to a new server, which subsequently brought the whole site down. When it came back up, most of my customizations were gone and I haven't yet figured out how to get them back. It's been a long day and I'm not sure how long this is going to take, so please bear with me. It seems more important to get the site up and running again even if it's suddenly in a minimalist guise. I'll tune it back up as time permits.

Kepler’s First Light

by Paul Gilster | Apr 17, 2009 | Exoplanetary Science | 8 Comments

'First light' from any new telescope is an exciting moment, but never more so than with the Kepler instrument. Dust cover off, the space-based telescope is now looking at its target, a starfield in the Cygnus-Lyra region of the Milky Way. Kepler's full field of view covers a 100-degree swath of sky, containing scenery like NGC 6791, an eight-billion year old cluster some 13,000 light years from us, as seen in the image below. Image: The area pictured is 0.2 percent of Kepler's full field of view, and shows hundreds of stars in the constellation Lyra. The image has been color-coded so that brighter stars appear white, and fainter stars, red. It is a 60-second exposure, taken on April 8, 2009, one day after the spacecraft's dust cover was jettisoned. Credit: NASA/JPL-Caltech. Loosely bound, the stars in NGC 6791 have begun to spread out from each other, the signature of what is called an 'open cluster.' The view is impressive but also blurry, an intentional effect that is being used,...

New Earths: A Crossroads Moment

by Paul Gilster | Apr 16, 2009 | Astrobiology and SETI, Autonomy and Robotics | 8 Comments

A symposium called Crossroads: The Future of Human Life in the Universe seems timely about now (the site has been down all morning but should be up soon). With the Kepler mission undergoing calibration and CoRoT actively searching for small extrasolar worlds, we're probably within a few dozen months of the detection of an Earth-like world around another star (and maybe, by other methods, much closer). This is sometimes referred to as the 'Holy Grail' of planetary sciences, but as soon as we accomplish it, a new 'Grail' emerges: The discovery of life on these worlds. And then another: Finding intelligent life. We can kick the Fermi Paradox around all day, and enjoyably so because it forces us to use our imaginations, but ultimately we hope to put together the hard data that will tell us which of our speculations is most accurate. I see that the Crossroads symposium, which will take place May 1-2 as part of the Cambridge Science Festival, will include Frank Drake's re-examination of...

Tuning in the Epsilon Eridani Channel

by Paul Gilster | Apr 15, 2009 | Culture and Society | 28 Comments

Seth Shostak's recent op-ed in the New York Times offers an unsettling title: 'Boldly Going Nowhere.' And Seth, an astronomer at the SETI Institute, gets right to his point: "...we're not about to breach the final frontier. Piling into a starship and barreling into deep space may long remain — like perfect children or effort-free bathroom cleaners — a pipe dream." The homely similes reinforce the theme, one that also surfaces in Shostak's new book Confessions of an Alien Hunter (National Geographic, 2009), which makes a strong case for continuing SETI as our digital capabilities expand. Indeed, given the daunting challenge of interstellar distances, it could be argued that our sole contact with extraterrestrial civilizations, if they exist, will take place through communications from afar, mediated by radio or light. Let's face it, the numbers are tough. The fact is that we can already do interstellar travel, provided we're content with transit times of many tens of...

An Unseen Nearby Star?

by Paul Gilster | Apr 14, 2009 | Outer Solar System | 27 Comments

It was Percival Lowell who suggested that anomalies in the orbit of Uranus might point to the existence of the body he called 'Planet X.' The discovery of Pluto in 1930 gave us confirmation of a planet beyond Neptune (since downgraded, of course), but the idea of other large bodies in the outer Solar System still has its appeal, and although we've found such interesting objects as Eris and Sedna, questions remain about what else might be found lurking at the fringes of the system. Theories of the Outer System Thus the active theorizing, which includes one study speculating on an Earth-sized planet at 100 to 170 AU, a body that would help to explain what we know about the architecture of the Kuiper Belt. Another investigation looked at a possible Mars-sized body at 60 AU, which would help us understand the distribution of various Trans-Neptunian Objects, a term that basically covers any object orbiting the Sun beyond Neptune. Other theories abound, one of which sees a giant planet...

Theia and the ‘Big Whack’

by Paul Gilster | Apr 13, 2009 | Deep Sky Astronomy & Telescopes | 15 Comments

The idea that the Moon was formed through the impact of a Mars-sized object with the early Earth (the 'big whack') has gained credibility over the years. Call it 'Theia,' a hypothetical planet that may have formed in our system's earliest era. And place it for argument's sake at either the L4 or L5 Lagrangian point, where the gravitational influences of other developing planets like Venus may have destabilized its orbit, accounting for the subsequent impact. It's an interesting notion that helps us to understand why the Moon has such a small iron core. In the early Solar System, both Theia and Earth would still have been molten, so that heavier elements like iron sank into their cores. The effect of the impact, say Princeton University's Edward Belbruno and Richard Gott, would have been to strip away primarily the lighter elements on the outer layers of the two planets, providing the building blocks for the Moon. Image: The Lagrangian points of the Earth-Sun system (note the James...

Closing the Data Gap

by Paul Gilster | Apr 10, 2009 | Culture and Society | 17 Comments

1951's The Man from Planet X is a creepy Edgar G. Ulmer film involving an inscrutable alien whose small craft falls to earth in the moors of Scotland. There he is attacked, exploited and ends up being killed in spite of the fact that his real mission was apparently peaceable. The film is noir-like, the sets foggy and surreal, and although the dialog positively creaks, the moody atmosphere still puts a chill up my spine. I mention this personal favorite because my copy of The Man from Planet X has a glitch, a defect in the aging tape that causes the image to jitter for a ten second period just as actress Margaret Field is getting progressively spooked by the strange alien craft. You would think that an upgrade to DVD is in order, and indeed, that's my only real choice. But the other night, watching a DVD of Alec Guinness in the delightful Our Man in Havana (1959), I saw the image lock up and freeze, decomposing into pixels that reconfigured themselves only after a couple of minutes...

Friedwardt Winterberg on Starship Design

by Paul Gilster | Apr 9, 2009 | Missions | 16 Comments

Imagine frozen pellets of deuterium and helium-3 being ignited by electron beams to produce fusion, all this occurring in a combustion chamber fully 330 feet in diameter. Such was one early concept for Project Daedalus, the British Interplanetary Society's starship design that would evolve into a two-stage mission with an engine burn -- for each stage -- of two years, driving an instrumented payload to Barnard's Star at twelve percent of the speed of light. We've been kicking the Daedalus concept around here recently because the BIS is developing, in conjunction with the Tau Zero Foundation, Project Icarus, a revisiting of the original Daedalus concept. The Daedalus propulsion system required fifty billion fuel pellets, thirty thousand tons of helium-3 and 20,000 tons of deuterium, as massive an undertaking as our species has ever attempted, given that the helium-3 would have to come from the atmosphere of a gas giant like Jupiter. Icarus will study what Daedalus might look like with...

Life’s Constituents Around M-Dwarfs

by Paul Gilster | Apr 8, 2009 | Exoplanetary Science | 15 Comments

Kepler's dust cover has now been jettisoned, meaning the search for extrasolar 'Earths' is not long from commencing. The cover stayed in place for so long because the spacecraft's photometer had to make measurements of electronic noise that will later have to be removed from the science data. Mission engineers will now continue with the calibration process for several weeks using images of actual stars. Our debates over the 'rare Earth' hypothesis will be getting firm data in short order because of Kepler. Three years from now, having had time to detect terrestrial-class planets in the habitable zone of their stars, confirm the detections and further examine the results, we should have at least a sense of how common such planets are. Finally we can move beyond informed speculation with the sort of hard data we need. And as far as the first terrestrial planet detection in the habitable zone, CoRoT may just beat Kepler to the punch. Meanwhile, the astrobiological side of the 'rare...

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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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