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Technological Leaps in Perspective

by Paul Gilster | Nov 30, 2011 | Culture and Society | 14 Comments

Wednesday is a travel day for me, and one with little chance to do any posting here. I'll leave you, then, with a quotation, and get back to normal posting tomorrow. Interstellar travel is incredibly difficult, perhaps as difficult to us today as a flight to Mars would have appeared to Christopher Columbus or other would-be transoceanic navigators 500 years ago. Indeed, the ratio of the distance from Earth to Mars compared to Columbus' voyage from Spain to the Caribbean -- 80,000:1 -- is roughly the same as the ratio of the distance to Alpha Centauri compared to a trip to Mars. Thus, the key missions required to establish humanity successively as a Type I, Type II, and Type III civilization all stand in similar relation to each other, and if the 500 years since Columbus have sufficed to multiply human capabilities to the point where we now can reach for Mars, so a similar span into the future might be expected to prepare us for the leap to the stars. Actually, it should not take so...

Cygnus X-1: A Black Hole Confirmed

by Paul Gilster | Nov 29, 2011 | Deep Sky Astronomy & Telescopes | 1 Comment

Cygnus X-1 is one of the strongest X-ray sources we can detect from Earth and the first widely thought to be a black hole. In fact, when Stephen Hawking bet against X-1 being a black hole back in 1975, he was more or less setting up a hedge, for black holes have been a crucial part of Hawking's work. Hawking writes about his wager with Kip Thorne entertainingly in the first edition of his A Brief History of Time (1988): This was a form of insurance policy for me. I have done a lot of work on black holes, and it would all be wasted if it turned out that black holes do not exist. But in that case, I would have the consolation of winning my bet, which would win me four years of the magazine Private Eye. If black holes do exist, Kip will get one year of Penthouse. When we made the bet in 1975, we were 80% certain that Cygnus was a black hole. By now, I would say that we are about 95% certain, but the bet has yet to be settled. Not long afterwards, the bet would be settled. If you go on...

Star Maker: The Philosophy of Olaf Stapledon

by Paul Gilster | Nov 28, 2011 | Culture and Society | 21 Comments

Kelvin Long and Richard Osborne have seen to it that the British Interplanetary Society's conference on the highly influential science fiction writer and philosopher Olaf Stapledon has gone off without a hitch. Here is their report from the event, a conference evidently as rife with speculation and far-future musings as anything the author himself ever penned. by K.F. Long & R. Osborne, Symposium Chairmen During the summer the British Interplanetary Society (BIS) played host to a symposium on World Ships, possibly the first such dedicated conference ever on these grand, long-term planning concepts. However, the most recent BIS symposium is on a topic that covers eons. There was no one who thought bigger and over longer timescales than the philosopher and writer Olaf Stapledon. Once again, the BIS has organized another first in history. On the 23rd of November members and visitors gathered to discuss the philosophy and literature of Stapledon in the context of today's current space...

Reflections on a Mythic Voyager

by Paul Gilster | Nov 25, 2011 | Culture and Society, Missions | 76 Comments

Voyager 2 received commands in early November to switch to the backup set of thrusters that control the roll of the spacecraft. I keep close tabs on the Voyagers because, still operational, they constitute our first interstellar mission, headed beyond the heliosphere and still returning data. Launched in 1977, they're an obvious example of long-term survival in space, an issue that will become increasingly visible as we plan for longer and deeper missions beyond our Solar System. We got word on November 5 that Voyager 2 has accepted the new commands. Let's talk about this first in terms of engineering. Behind the switch is the need to reduce operating power, for using the backup thruster pair that controls roll motion will let engineers turn off the heater that warms the fuel line to the primary thruster, saving about 12 watts of power. With Voyager 2's power supply providing about 270 watts, finding savings like this can help the spacecraft remain operational. It's remarkable to...

Ranking Exoplanet Habitability

by Paul Gilster | Nov 23, 2011 | Exoplanetary Science | 27 Comments

Our notions of habitability are built around environments like our own, which is why the search for planets with temperatures that support liquid water at the surface is such a lively enterprise. But as we saw yesterday, it is not beyond possibility that many places in our Solar System could have sub-surface oceans, even remote objects in the Kuiper Belt. And that raises the question of how we assess astrobiological environments, an issue studied by Dirk Schulze-Makuch (Washington State University) and Abel Mendez (University of Puerto Rico at Arecibo), working with an international team of researchers in a paper suggesting a new approach. Schulze-Makuch makes the situation clear: "Habitability in a wider sense is not necessarily restricted to water as a solvent or to a planet circling a star. For example, the hydrocarbon lakes on Titan could host a different form of life. Analog studies in hydrocarbon environments on Earth, in fact, clearly indicate that these environments are...

The Case for Pluto’s Ocean

by Paul Gilster | Nov 22, 2011 | Outer Solar System | 19 Comments

Sub-surface oceans in the Solar System may be far more common than we've realized. We've grown used to contemplating water under the ice of Europa, but similar oceans may well exist on Ganymede and Callisto, and there are signs of a possible ocean beneath Titan, not to mention the unusual activity we continue to observe on Enceladus. Where liquid water in cold objects seems least likely is in the Kuiper Belt, but Guillaume Robuchon and Francis Nimmo (University of California at Santa Cruz) have been making the case for an ocean inside distant Pluto, based on their models of thermal evolution and the behavior of the ice shell. As this article in Astrobiology Magazine points out (and thanks to my friend Antonio Tavani for the pointer to this one), Pluto's outer surface is a thin shell of nitrogen ice covering a shell of water ice. With New Horizons inbound to Pluto/Charon for an April, 2015 encounter, the researchers have been working out what surface features might help us make the...

Notes & Queries 11/21/11

by Paul Gilster | Nov 21, 2011 | Uncategorized | 4 Comments

Millis on The Space Show Marc Millis is now in Brussels for another TEDx talk -- I link here to the TEDx description of him as 'a rock star in the world of space geeks' that always gives him a chuckle. More about the talk as soon as I have the link for online viewing. All this reminds me to tell you that Marc and I were guests on David Livingston's The Space Show last week, with the MP3 now available at David's site. Although we did kick around some interstellar propulsion concepts, particularly in the call-in segments, we spent most of the time talking about Tau Zero and the 100 Year Starship project. If you want to hear about the nuts and bolts of Tau Zero including the interesting and developing university affiliations, check out the two-hour podcast. David is a superb interviewer. SF and the Sublime Gregory Benford recently posted Peter Nicholls' Big Dumb Objects and Cosmic Enigmas, a talk delivered in 1997 aboard the Queen Mary (now anchored at Long Beach, CA) on his site. Given...

Science Fiction and the Interstellar Idea

by Paul Gilster | Nov 18, 2011 | Culture and Society | 58 Comments

Science fiction has been much on my mind of late, particularly following the 100 Year Starship Symposium, where so many of the scientists I talked to mentioned novels and movies that had been influential in getting them into science. My friend Keith Cooper, editor of Astronomy Now and a fine science writer whose work I often cite in these pages, also shares an interest in SF, and it was natural enough that we fell into a conversation by email on how the genre relates to interstellar studies. Because while we would expect a natural synergy between science and science fiction, the genre's cinematic and literary treatments are often at variance with each other. Why is this, and why are some elements of the interstellar idea easier to explore in writing than in film? Here are some thoughts (and memories) about science fiction's role. Paul Gilster Keith, you and I are both science fiction readers, although I'm enough old that I grew up in the heyday of Heinlein and all those great books...

A Possible Subsurface Lake on Europa

by Paul Gilster | Nov 17, 2011 | Outer Solar System | 23 Comments

An area of disrupted terrain called Thera Macula on Jupiter’s moon Europa may be evidence for a body of liquid water with the volume of North America’s Great Lakes encased within the ice. The notion comes from analysis of floating ice shelves that seem to be collapsing. That an ocean exists beneath the ice on Europa should surprise no one, but what is significant about the recent findings is that they suggest a way to exchange nutrients and energy between the surface and the ocean beneath. Such a mechanism changes the nature of the speculation about whether Europa’s ice is thick or thin. The case for astrobiology always seemed stronger if the ice were thin, but it seems that ways to exchange material with the surface may exist in either scenario. At least that’s what this intriguing finding suggests. Britney Schmidt (University of Texas at Austin) is lead author on the paper that appears online in Nature: "One opinion in the scientific community has been, 'If the ice shell is thick,...

Updating the Gravitational Wave Hunt

by Paul Gilster | Nov 16, 2011 | Deep Sky Astronomy & Telescopes | 15 Comments

The Laser Interferometer Space Antenna mission (LISA), slated for launch later this decade, will go about testing one of Einstein's key predictions, that gravitational waves should emanate from exotic objects like black holes. Detectors like the Laser Interferometer Gravitational Wave Observatory (LIGO) have operated on Earth's surface but are subject to seismic noise that disturbs the observations in some of the key frequency ranges. The hope is that the space-based LISA will be able to go after the low-frequency gravitational wave spectrum to detect such things as the collision of black holes, the merger of galaxies or the interactions of neutron star binary systems. The good news out of the European Space Agency is that the LISA Pathfinder precursor mission, planned for a 2014 launch, is showing the accuracy needed to demonstrate what the more sophisticated LISA mission should be able to do. LISA Pathfinder is a small spacecraft unable to make a direct detection of gravitational...

Can Project Orion Be Re-Born?

by Paul Gilster | Nov 15, 2011 | Advanced Rocketry | 56 Comments

Project Orion keeps surfacing in propulsion literature and making the occasional appearance on the broader Internet. A case in point is a vigorous defense of Orion-style engineering by Gary Michael Church on the Lifeboat Foundation blog. Church is rightly taken with the idea of propelling payloads massing thousands of tons around the Solar System, but he’s also more than mindful of the realities, both political and economic, that have kept Orion-class missions in the realm of the theoretical. It was, after all, the nuclear test ban treaties of the Cold War era that brought the original project to a close, and anti-nuclear sentiment remains strong in the public today. But the Orion idea won’t go away because it is so tantalizing. Church runs through the relevant information, much of it familiar to old Centauri Dreams hands. Freeman Dyson and Ted Taylor were working on a concept in which a large percentage of the energy of a nuclear explosion -- these are small nukes of the kind Taylor...

An Asteroid Born Near the Earth

by Paul Gilster | Nov 14, 2011 | Asteroid and Comet Deflection | 2 Comments

This morning we stick with the planetary migration theme begun on Friday, when the subject was a possible ice giant that was expelled from the Solar System some 600 million years after formation. We have a lot to learn about the mechanisms that could force such ejections, but it's becoming clear that objects up to planet size do indeed migrate, as witness the latest findings on the asteroid Lutetia. Using spectral information put together from space- and ground-based telescopes including ESA's Rosetta spacecraft, scientists have determined that Lutetia is a fragment of the same inner system material that went into the inner rocky planets. A gravitational encounter somewhere in the inner system would then have propelled it outward to the Main Belt. The observations pulled together data in visible, ultraviolet, near-infrared and mid-infrared wavelengths. The only kind of meteorite that matches the spectrum of Lutetia exactly is the type known as enstatite chondrites, known to be...

A Gas Giant Ejected from our System?

by Paul Gilster | Nov 11, 2011 | Outer Solar System | 30 Comments

Free-floating planets -- planets moving through interstellar space without stars -- may not be unusual. If solar systems in their epoch of formation go through chaotic periods when the orbits of their giant planets are affected by dynamical instability, then ejecting a gas giant from the system entirely is a plausible outcome. David Nesvorny (SwRI) has been studying the possibilities for such ejections in our Solar System, using computer simulations of the era when the system was no more than 600 million years old. Clues from the Kuiper Belt and the lunar cratering record had already suggested a scattering of giant planets and smaller bodies then. An ejected planet makes sense. Studies of giant planets interacting with the protoplanetary disk show that they tend to migrate and wind up in a configuration where pairs of neighboring planets are locked in a mean motion resonance. Such a resonance occurs when two planets exert a regular, periodic gravitational influence on each other...

A Look at Methane-Based Life

by Paul Gilster | Nov 10, 2011 | Astrobiology and SETI | 30 Comments

Could life exist on a world with a methane rather than a water cycle? The nitrogen-rich atmosphere of Titan, laden with hydrocarbon smog, is a constant reminder of the question. Cassini has shown us the results of ultraviolet radiation from the Sun interacting with atmospheric methane, and we've had radar glimpses of lakes as well as the haunting imagery from the descending Huygens probe. Our notion of a habitable zone depends upon water, but adding methane into the mix would extend the region where life could exist much further out from a star. Chris McKay and Ashley Gilliam (NASA Ames) have been actively speculating on the possibilities around red dwarfs and have published a recent paper on the subject. It's intriguing, of course, that with methane we get the 'triple point' that allows a material to exist in liquid, solid or gaseous form at a particular temperature and pressure. That makes Titan 'Earthlike' in the sense that our initial view showed a landscape with the clear signs...

Pluto/Charon: A Dangerous Arrival?

by Paul Gilster | Nov 9, 2011 | Outer Solar System | 15 Comments

We've often considered the effect of interstellar dust on a spacecraft moving at a substantial percentage of the speed of light. The matter becomes even more acute when we consider an interstellar probe arriving at the destination solar system. A flyby mission moving at ten percent of the speed of light is going to encounter a far more dangerous environment just as it sets about its critical observations, which is why various shielding concepts have been in play to protect the vehicle. But even at today's velocities, spacecraft can have unexpected surprises when they arrive at their target. We're now looking toward a 2015 encounter at Pluto/Charon. New Horizons is potentially at risk because of the fact that debris in the Pluto system may not be found in a plane but could take the form of a thick torus or even a spherical cloud around the system. We don't yet know how much of a factor impactors from the Kuiper Belt may be, but strikes at 1-2 kilometers per second would kick up...

2005 YU55 Closest Approach Today

by Paul Gilster | Nov 8, 2011 | Asteroid and Comet Deflection | 4 Comments

2005 YU55, an asteroid roughly the size of a city block, makes its closest pass today, approaching within 325,000 kilometers, closer than the distance between the Earth and the Moon. It will be another seventeen years before we get an asteroid as substantial as this in such proximity. That one is 2001 WN5, which will pass halfway between the Moon and the Earth in 2028. Today's object of interest, 2005 YU55, isn't in danger of hitting the Earth on this pass, but astronomers track these objects closely because over time their trajectories are known to change. Image: This radar image of asteroid 2005 YU55 was obtained on Nov. 7, 2011, at 11:45 a.m. PST (2:45 p.m. EST/1945 UTC), when the space rock was at 3.6 lunar distances, which is about 860,000 miles, or 1.38 million kilometers, from Earth. Image credit: NASA/JPL-Caltech. The asteroid's discoverer, Robert McMillan (University of Arizona) calls it "...one of the potentially hazardous asteroids that make close approaches from time to...

The Light of Alien Cities

by Paul Gilster | Nov 7, 2011 | Astrobiology and SETI | 59 Comments

If you're looking for a new tactic for SETI, the search for extraterrestrial intelligence, Avi Loeb (Harvard-Smithsonian Center for Astrophysics) and Princeton's Edwin Turner may be able to supply it. The duo are studying how we might find other civilizations by spotting the lights of their cities. It's an exotic concept and Loeb understates when he says looking for alien cities would be a long shot, but Centauri Dreams is all in favor of adding to our SETI toolkit, which thus far has been filled with the implements of radio, optical and, to a small extent, infrared methods. Image: If an alien civilization builds brightly-lit cities like those shown in this artist's conception, future generations of telescopes might allow us to detect them. This would offer a new method of searching for extraterrestrial intelligence elsewhere in our Galaxy. Credit: David A. Aguilar (CfA). Spotting city lights would be the ultimate case of detecting a civilization not through an intentional beacon but...

Millis: Of Time and the Starship

by Paul Gilster | Nov 4, 2011 | Culture and Society | 50 Comments

What next for the 100 Year Starship Study? NASA and the Defense Advanced Research Projects Agency will make the call, as Tau Zero founder Marc Millis told Alan Boyle in his recent interview. To talk to Boyle, Millis donned virtual garb and appeared in Second Life in robotic form, but the interview is now available as a podcast on BlogTalkRadio and iTunes. I'll send you there for the discussion in full, but do note that Boyle talked to Millis about starflight before the show and has made an edited transcript of that conversation available on Cosmic Log. The quotes I use below are from the earlier talk, but do pick up the podcast and listen to the whole thing. Where DARPA goes next is to make a decision about awarding the funds remaining from the $1 million originally put into the project. About $500,000 is available, and Centauri Dreams speculates that DARPA will be more than happy to allocate the funds and be done with them, thus removing 'starship funding' from a budget always...

Dying Stars and their Planets

by Paul Gilster | Nov 3, 2011 | Exoplanetary Science | 24 Comments

Although I can't make the journey just then, I wish I could attend an upcoming conference at Arecibo (Puerto Rico) called Planets around Stellar Remnants. The meeting takes place twenty years after the discovery of the first exoplanets, the worlds orbiting the millisecond pulsar PSR B1257+12. I've been interested in the fate of planets around older stars ever since reading H.G. Wells' The Time Machine as a boy and encountering his image of a swollen, dying Sun. We also have interesting questions to ask about the kind of planets that exist around white dwarfs, and whether new planets (and chances for life) may eventually occur in their systems. It's appropriate that the conference be organized by Penn State, for it was that university's Alexander Wolszczan, working with Dale Frail of the National Radio Astronomy Observatory, who made the discovery of those two and possibly three planets that launched the modern exoplanet era. Nor has Wolszczan slowed in his efforts. The most recent...

Notes & Queries 11/2/11

by Paul Gilster | Nov 2, 2011 | Culture and Society | 11 Comments

Tau Zero in Second Life I have almost no experience with online virtual worlds like Second Life, but I do want to mention that Marc Millis will appear later today (Nov. 2) on the ‘Virtually Speaking’ talk show program, which can be accessed here as well as in Second Life. The focus of the interview is to be on prospects for interstellar travel, what a program like the 100-Year Starship can do, and what Tau Zero and other efforts (such as Project Icarus) are all about. The show begins at 9 PM Eastern time (0200 UTC) this evening, and may wind up being audio-only if the Second Life bit doesn’t work out. I’m sure it will, but Marc is as new to Second Life as I am, and my last experience with the medium had me wandering around in an enormous virtual house trying to find someone with whom I was supposed to be doing an online interview, and I remember being alternately intrigued and baffled by the options available to me. Old time Second Lifers will find this bizarre, I’m sure, but some of...

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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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