Red dwarf stars of the sort we discussed yesterday are all over the galaxy, comprising perhaps as much as 80 percent of the stellar population. Brown dwarfs are different. Data from the Wide-Field Infrared Survey Explorer mission (WISE) indicate that these ‘failed’ stars -- brown dwarfs are too small to sustain hydrogen fusion -- exist in smaller than expected numbers, at least in our stellar neighborhood. WISE could find but one brown dwarf for every six stars (see Brown Dwarfs Sparser than Expected for more on the WISE findings). Image: Brown dwarfs in relation to the Sun and planets. Credit: NASA/WISE mission. As we learn more about the brown dwarf population, we can keep in mind the tantalizing fact that several of these objects have been found with disks of material around them, leading to the speculation that they can form planets in the same way that normal stars can. It’s true that several objects have already been found associated with brown dwarfs, but they tend to be large...
Climate Models for Red Dwarf Planets
Although it's hard for me to believe it, there was a time nine years ago, not long after I began writing these posts, when a daily scramble for topics was fairly common. How the world has changed. These days, between the huge increase in online discussion of interstellar flight and the burgeoning exoplanet scene, the problem becomes to keep from falling too far behind. I'm already a couple of weeks out on interesting work from the University of Washington on one of my favorite topics, red dwarfs and the possibilities for life there. It's time to catch up. What Aomawa Shields has been examining in her recent work is climate in the extreme, the kind of 'snowball Earth' event that, in several periods 600 million years ago and earlier, may have covered the planet in ice from pole to pole. Shields' new paper in Astrobiology goes at the question of climate extremes on planets around M-dwarfs, where conditions are markedly different than around stars like the Sun. It turns out that M-dwarf...
Remembering The Listeners
Back in the 1970s I ran across an essay by James Gunn called "Where Do They Get Those Crazy Ideas," which was all about how science fiction worked and where its writers sought inspiration. I had long admired Gunn, a college professor who was developing a body of critical work on science fiction even as he continued to publish taut, interesting stories like those I had seen collected in Station in Space (1958) and The Joy Makers (1961). A story first published in Galaxy called "The Cave of Night" had particularly haunted me and led me to seek out more of his work. On the spur of the moment, I wrote Gunn a brief note of appreciation for the essay on writing, not thinking I would hear back from him, but sure enough a letter swiftly appeared inviting me to come to Kansas that summer, where he would be leading a science fiction workshop. That was a trip I wasn't able to schedule, but I kept an eye on Gunn's writing and finally, some years after its publication, sat down to read The...
The Milky Way’s Library
This is as strange a maze as e'er men trod, And there is in this business more than nature Was ever conduct of. That's Alonso in Shakespeare's late masterpiece The Tempest, a king of Naples who finds himself on a remote island where Prospero weaves his magical powers. It's an apt passage for Timothy Ferris to quote in his chapter "The Central Nervous System of the Milky Way," a part of the 1992 collection The Mind's Sky that was the basis of yesterday's post. For in an unusual conclusion to the essay, Ferris wonders whether the real purpose of a galactic network (and hence an ultimate goal of SETI) isn't passing along not only our science but our broader culture to other civilizations. "Who knows what importance our existence, or some shard of our thought, might have to a scholar or artist --- whether biological or artificial in origin -- in a remote galaxy in some far-future time?" It's a pleasing thought for a species used to feeling dwarfed by the universe, and it would apply to...
Finding the Galactic Internet
Greg Egan, a jewel in Australia's science fiction crown, writes in his 1997 novel Diaspora about a mind-bending far future scenario for interstellar travel. The human race has split into those still in biological bodies, those embedded in humanoid robots, and those who choose to live as software running on central computers. I won't get into the rich details of the novel this morning, but suffice it to say that the diaspora portrayed here involves a thousand clones of a future Earth community sent to explore nearby stars. Different digitized copies of the same characters spin out their own story lines over a background that spans hundreds of light years. This is one way to get to the stars, reminiscent of Robert Freitas' nanotech probes that house thousands of human intelligences in spacecraft no larger than needles. It's a reminder that highly advanced future cultures may have means at their disposal for star travel even if we find no way of getting up to more than a small...
While He’s Away…
Although I'm taking a break from posting, a recent note from Marc Millis suggests something productive that can happen while I'm gone. The founding architect of the Tau Zero Foundation and former head of NASA's Breakthrough Propulsion Physics project, Marc deals with the issues he asks about below on a daily basis, and so do I. But compiling accurate, non-conflicting information about them can be tricky, which is why we could use your help. Read on. by Marc Millis While Paul is away, I have a request for you. We have a number of questions for which we need some help to find reliable answers. For all of you who have been wanting to help, here now is a chance. When answering these questions, we need to know where you got the information. Please cite the document where you found the information. We are looking for reliable information, so avoid articles that cite values to advocate a particular solution. We have found that some papers skew estimates for such things so that it will...
Summer Break for Centauri Dreams
The charged air of mid-July in the northern hemisphere creates states of mind that can be both nostalgic and surreal. Ray Bradbury always knew how to catch these. Listen: Somewhere, a book said once, all the talk ever talked, all the songs ever sung, still lived, had vibrated way out in space and if you could travel to Far Centauri you could hear George Washington talking in his sleep or Caesar surprised at the knife in his back. So much for sounds. What about light then? All things, once seen, they didn't just die, that couldn't be. It must be then that somewhere, searching the world, perhaps in the dripping multiboxed honeycombs where light was an amber sap stored by pollen-fired bees, or in the thirty thousand lenses of the noon dragonfly's gemmed skull you might find all the colors and sights of the world in any one year. Or pour one single drop of this dandelion wine beneath a microscope and perhaps the entire world of July Fourth would firework out in Vesuvius showers... I love...
A Blue Planet Nothing Like Our Own
Rayleigh scattering is what happens when light is scattered by particles considerably smaller than the light’s wavelength. Although it can happen in solids and liquids, it’s most obvious when it occurs in our sky, causing its blue color. We’re seeing the short blue wavelengths of sunlight scattered by oxygen and nitrogen molecules in the atmosphere, while red wavelengths are absorbed more strongly, hence less scattering. When you leave the atmosphere and go into space, the Earth appears blue because the oceans absorb red and green wavelengths more than blue ones, and thus we can see the reflected blue color of our sky. But colors from within the atmosphere or beyond it depend on local conditions. The reddish sky shown by the Viking landers in 1977 was the result of iron-rich dust thrown up by the dust storms that are endemic to the planet. We can assume that the color of other planets as seen from space -- think Jupiter or Venus -- is the result of particles within their atmospheres....
Perspectives on Pluto and Charon
We're just past the 35th anniversary of the discovery of Pluto's moon Charon. Or more precisely, we just passed the July 7 date when the announcement of that discovery, which had actually happened in June of 1978, was made. That turned my thoughts back to Larry Niven's story "Wait It Out," which tells the tale of two astronauts who are stranded on Pluto's surface. Removing his helmet to die quickly, the narrator discovers that he lives on in a strange semi-stasis, his brain now a superconductor. First published in 1968 (in All the Myriad Ways), the story contains no Charon, but the scene lingers with me. I'll quote just a patch of it, though I've quoted it before: A superconductor is what I am. Sunlight raises the temperature too high, switching me off like a damned machine at every dawn. But at night my nervous system becomes a superconductor. Currents flow; thoughts flow; sensations flow. Sluggishly. The one hundred and fifty-three hours of Pluto's rotation flash by in what feels...
Prophecy, Prediction and Starflight
I'm looking forward to the upcoming Starship Congress hosted by Icarus Interstellar, which will take place in Dallas from August 15th to the 18th at the Hilton Anatole. With an audience of physicists, engineers and researchers of all kinds, this is a chance to catch up with old friends and firm up relationships that have in some cases been pursued solely through email. 2013 may be remembered as the year of the conference in interstellar terms, since we had the Tennessee Valley Interstellar Workshop in February, Starship Century in May, Starship Congress coming up in August, then the 100 Year Starship Symposium in Houston from September 19th to the 22nd. This doesn't include smaller events like the British Interplanetary Society's excellent Philosophy of the Starship gathering in late May, and if you're in range of BIS headquarters in London, it's worth checking out what's coming up on their always active schedule. But thoughts of indefatigable activity on the interstellar front...
‘A Terrible Beauty’ Among the Stars
Martin Rees' ideas on how humans will adapt to starflight, discussed here yesterday, offer plenty of ground for speculation and good science fiction. After all, the path ahead forks in many directions, one of them being the continuing development of artificial intelligence to the point where 'artilects' rather than humans become the logical crew for star missions. If decades or even centuries are needed to cross to another system, then this gets around the problem of keeping people sane and cooperating across what might be generations of voyaging. Another fork is biological, with humans being gradually engineered to make them more adaptable to environments they'll find at their destination. Here we can imagine crews sent out in some kind of deep hibernation, their biology tweaked to allow a ready transition to the new planet. Or perhaps cyborg solutions suggest themselves, with humans augmented by digital technologies to deal with problems and interface directly with critical...
Starflight: Engagement with Risk
How we'll go to the stars is often a question we answer with propulsion options. But of course the issue is larger than that. Will we, for example, go as biological beings or in the form of artificial intelligence? For that matter, if we start thinking about post-human intelligence, as Martin Rees does in the recently published Starship Century, are we talking about reality or a simulation? As the Swedish philosopher Nick Bostrom has speculated, a supremely advanced culture could create computer simulations capable of modeling the entire universe. Rees recapitulates the argument in his essay "To the Ends of the Universe": A culture that could create simulations as complex as the universe we live in might create virtual universes in the billions as a ripe domain for study or pure entertainment, allowing a kind of 'time travel' in which the past is reconstructed and the simulation masters can explore their history. So there we have a play on the nature of reality itself and the notion...
Red Dwarfs: Clouds in the Habitable Zone
How close can a planet be to its star and still be habitable? If by ‘habitability’ we mean liquid water on the surface, with whatever consequences that may bring on a particular world, then it’s clear that the answer is partially dependent on clouds. We’ve developed one-dimensional models that can study the effect of clouds in various exoplanet environments, but they’re unable to predict cloud coverage, location or altitude. A new paper now describes a three-dimensional model that can make such calculations about atmospheric circulation, with interesting results. Focusing on planets around M-class dwarf stars, Jun Yang and Dorian Abbot (both of the University of Chicago) and Nicholas Cowan (Northwestern University) are quick to note that red dwarfs like these constitute perhaps 75 percent of all main sequence stars. Current data (based on the work of Courtney Dressing and David Charbonneau) suggest that there is an abundance of Earth-size planets in the habitable zone -- one per star...
Focus on the Sail
The British geneticist and biologist J.B.S. Haldane has left us with one of the more memorable lines about scientific inquiry, one that draws on the richest of all of Shakespeare's plays for its punch. Hamlet tells Horatio that there are more things in heaven and Earth than are dreamt of in his philosophy (Act 1, Sc. 5), a thought Haldane adapts in the service of intellectual surprise. In his collection Possible Worlds and Other Essays (1927), he writes: I have no doubt that in reality the future will be vastly more surprising than anything I can imagine. Now my own suspicion is that the universe is not only queerer than we suppose, but queerer than we can suppose ... I suspect that there are more things in heaven and earth than are dreamed of, or can be dreamed of, in any philosophy. We can imagine Olaf Stapledon nodding as he read those lines. Haldane sketched out a human history covering the coming 40 million years in his essay "The Last Judgement," one that Stapledon drew on in...
Into the Literature of Starflight
Tracking down starflight in literature is an absorbing pastime. When I was writing my Centauri Dreams book, I found that I was vaguely familiar with many of the antecedents of today's science fictional journeys, but a book called Wunderwelten, by Friedrich Wilhelm Mader, took me by surprise. A 1911 adventure novel for young readers, Wunderwelten imagines a sphere that, in the fashion of the time's space fiction, was moved by antigravity in a multi-year journey to Alpha Centauri. Mader's ship, called 'Sannah,' was a precursor to all the Centauri-bound starships to come. What a delight to find Sannah emerge in the form of Sannah III in Stephen Baxter's story "Star Call," which appears in the recently published Starship Century. But Baxter's updated ship is a far cry from the 50-meter antigravity vessel imagined by Mader. For one thing, it's gifted with artificial intelligence: I am called Sannah III because I am the third of four copies who were created in the NuMind Laboratory at the...
Starship Century: A Review of the Book
Could there be a more time-worn trope in science fiction than the arrival of colonists or explorers on a new world? The stage is set for adventure and the unwinding of whatever plot theme the author has in mind, but if the planet is Earth-like, we see the colonists quickly settling in, adapting to local conditions and, in relatively short order, creating a new society. Back in the 1950s the film When Worlds Collide showed the arrival of desperate survivors of a doomed Earth on a planet that would be their refuge, the assumption being that from this point on, everything would be no more difficult than setting up a camp on some new continent. Would it be so? For that matter, would our human crew be able to survive the journey? Paul Davies has his doubts, and he expressed them forcefully at the recent Starship Century event in San Diego. While we tend to concentrate on time and distance problems -- how do you get something moving fast enough to get your crew to another star within a...