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Hawking: The Need for an Interstellar Mission

by Paul Gilster | Nov 30, 2006 | Antimatter, Culture and Society | 35 Comments

About to receive the Royal Society's Copley Medal, Britain's highest scientific award, Stephen Hawking told a BBC radio audience that if the human race were to survive, it would be necessary to go to another star. Here's a quote from a story on this in the Daily Mail: "The long-term survival of the human race is at risk as long as it is confined to a single planet... Sooner or later, disasters such as an asteroid collision or nuclear war could wipe us all out. But once we spread out into space and establish independent colonies, our future should be safe. There isn't anywhere like the Earth in the solar system, so we would have to go to another star." Hawking acknowledges the immense problems, telling his interviewer that chemical rockets like the Saturn V used on Apollo would require tens of thousands of years to reach Alpha Centauri. And while he has an admiration for Star Trek's warp drive (and is quite a fan of the series, as Trekkies know), Hawking pins his hopes on antimatter,...

Close Pass Through a Stellar Magnetosphere

by Paul Gilster | Nov 29, 2006 | Exoplanetary Science | 4 Comments

Tau Boötis, a billion year old star some 50 light years from Earth, would be a fascinating place to see up close. The star is orbited by a gas giant some 4.4 times Jupiter's mass, one of those 'hot Jupiters' that close to improbably tight distances with the primary. In this case, the planet/star separation is a mere 0.049 AU, making it about 5 percent of the distance between the Earth and the Sun. 'Hot Jupiters' are bound to be dramatic objects anyway, but this one has other attributes. A team of French astronomers has been able to measure the magnetic field of Tau Boötis itself, finding it just slightly larger than the Sun's. That's the first direct measurement of the magnetic field of a star hosting an exoplanet, and it sets up interesting studies of the interactions between the two bodies as the planet moves so breathtakingly close to its star. Image: An artist's conception of the giant exoplanet orbiting Tau Boötis through the star's magnetic archs. Credit David Aguilar, CfA. In...

Star Mission of a Lifetime

by Paul Gilster | Nov 28, 2006 | Culture and Society, Missions | 19 Comments

We seem to have accepted in our time the notion that technology always moves forward. But a key factor in the Drake Equation, that long and interesting conjecture that parses the possibilities for extraterrestrial life, is the question of whether technological societies have an average lifetime. Do they invariably survive to reach the stars, or do they destroy themselves before this is possible? Listen to something Fred Hoyle said back in 1964: It has often been said, if the human species fails to make a go of it here on Earth, some other species will take over the running. In a sense of developing high intelligence, this is not correct. We have, or will have, exhausted the necessary physical prerequisites so far as this planet is concerned. With coal gone, oil gone, high-grade metallic ores gone, no species however competent can make the long climb from primitive conditions to high-level technology. This is a one-shot affair. If we fail, this planetary system fails so far as...

Are Other Solar Systems Like Our Own?

by Paul Gilster | Nov 27, 2006 | Exoplanetary Science | 8 Comments

We've identified over 200 planets around other stars, but in many ways we know little about other solar systems. The problem is in extrapolating from our knowledge of one or two planets to an entire planetary system, much of which we cannot detect. Can we expect to find gas giants mixed with small terrestrial worlds around most Sun-like stars? And what about the smaller and far fainter red dwarfs? Clearly, the job of characterizing not just planets but entire systems is going to occupy astronomers for many a decade. A new paper from the California & Carnegie team takes helpful steps in that direction. New planet finds are always fascinating, and the team does have four of them, the highlight being the pair orbiting the Sun-like star HIP 14810. Greg Laughlin (UC-SC) writes about that system on the systemic site, noting this: The fact that the orbit is clearly non-circular would be strong evidence for the presence of planet c, even if there weren't enough data to detect c directly. If...

Fine-Tuning Our View of Orion

by Paul Gilster | Nov 25, 2006 | Deep Sky Astronomy & Telescopes | 1 Comment

It's a gorgeous day in the mid-Atlantic states following one of the most colorful autumns in memory. Most of the leaves are down now, which gives me plenty to do. I had intended to look at the new paper from the California & Carnegie planet finder team, but the great outdoors beckons. Instead, we'll examine their latest next week, along with more on interstellar flight scheduling with reference to Marc Millis' recent presentation at Princeton and an intriguing Fred Hoyle insight. For today, here's a quick post on how adaptive optics can sharpen a telescope's view. In the image below, you're seeing two views of the part of the Orion Nebula known as the Trapezium. The Subaru telescope on Mauna Kea (Hawaii), working without adaptive optics, obtained the image on the right back in 1999. The image on the left shows the effect of a new laser guide star system and enhanced AO, and as you can see, the difference in detail is remarkable. Be sure to click to enlarge both views. Image: The...

Barnard’s Star and the ‘Wait Equation’

by Paul Gilster | Nov 24, 2006 | Culture and Society, Missions | 26 Comments

When do you decide to launch a starship? It's a question based as much on cultural assumptions as technology. Start with the premise that we can ratchet up today's velocities to 150 kilometers per second, roughly ten times the speed at which New Horizons will cross Pluto's orbit. If we want to send a probe six light years to Barnard's Star at that speed, we would be looking at a travel time of 12,000 years. That's a lot of time, but better than Voyager's 70,000-year plus travel time to the Centauri stars (if either Voyager were pointed in their direction). Clearly, 12,000 years is too many, especially in an age that regards maximum mission time as the lifetime of a researcher working on the project. Besides, if we did launch that kind of mission, it would inevitably be passed enroute by a faster spacecraft. And that's the conundrum: does there ever come a time when you do launch, or are you always waiting for better propulsion systems and faster travel times? As Andrew Kennedy...

Clumpy Dark Matter in New Simulations

by Paul Gilster | Nov 22, 2006 | Exotic Physics | 9 Comments

More on growth scenarios for interstellar flight soon. But I don't want to let the recent dark matter news get past us, so a quick nod to the University of California at Santa Cruz, where researchers have run a powerful computer simulation to probe the dark matter halo that evidently surrounds our Milky Way. It's a further step toward understanding the stuff that makes up 82 percent of the matter in the universe, and that in turns helps us see how the large scale structure of the cosmos has evolved. Image: Density map of dark matter in a halo the size of the Milky Way galaxy's dark matter halo. Credit: J. Diemand, UC-SC. I grew up in a time when it was thought that everything in the cosmos was explicable through gravitational forces produced by objects we could see. From solar systems on up to galaxies, it made sense -- and the textbooks did this quite neatly with colorful diagrams -- to show how matter found its way into configurations that would turn into celestial objects visible...

Growing Our Way to Centauri

by Paul Gilster | Nov 21, 2006 | Culture and Society | 5 Comments

In a book so stuffed with insights and quirky oddments that it belongs on the shelf of anyone interested in interstellar flight, Carl Sagan and I.S. Shklovskii once made a stunning calculation. Their 1966 volume Intelligent Life in the Universe (San Francisco: Holden-Day) presents the argument that with an average annual growth rate of just 1/3 of one percent, energy demand will outstrip the total solar radiation falling on the Earth by a factor of 100,000 within 2500 years. The re-building of the Solar System into something like a Dyson sphere may be inevitable. But isn't it a pipe dream to assume that growth will continue at even these modest levels? That was certainly my initial response, for so many things can throw a spanner into a civilization's works. But Andrew Kennedy (The Chronolith Project, Seville Spain) takes a hard look at growth issues in a recent paper with interesting results. Kennedy believes that growth is far more tenacious than generally accepted. Economic...

An Economic Answer to the Fermi Paradox?

by Paul Gilster | Nov 20, 2006 | Culture and Society, Sail Concepts | 67 Comments

Those who ponder the Fermi Paradox might want to consider Myrhaf's solution, one based on economics. If advanced technolgical civilizations really are out there, maybe they simply can't afford to build interstellar spacecraft. Myrhaf assumes that the only realistic way to travel between the stars is via a slow generation ship, what Isaac Asimov once called a 'spome' or 'space home.' And he doubts anyone would attempt it. Expensive? You bet. And maybe there's no one with the deep pockets to build it. Governments are too inefficient, while capital investment is unlikely because interstellar travel has such a long timeline. Corporate heads looking for return on their investments aren't likely to have enough patience for a slow boat to Centauri. Charity? Perhaps there's a hope through what Myrhaf calls 'committed visionaries,' but we're talking investment over the course of generations. Does any culture have that kind of long-term vision once it develops the technologies that could build...

Between COROT and New Worlds

by Paul Gilster | Nov 18, 2006 | Exoplanetary Science | 1 Comment

If we're lucky, the COROT mission, to be launched December 21, will be the first to detect rocky planets not much larger than the Earth around other stars. We've looked at COROT recently, and discussed how it and the Kepler space telescope will use transit methods to find these distant worlds. But as you go beyond Kepler (to be launched in 2008), the need for new technologies becomes apparent, which is why planet-finder designs like New Worlds are so significant. Now I see that Claude Catala (Observatoire de Paris-Meudon) is proposing a new take on space-borne telescopes for this purpose. Catala suggests a survey that would gather light from literally hundreds of 10-centimeter telescopes working in tandem (COROT itself is built around a single 27-centimeter telescope). These are small instruments, to be sure, and in some ways less impressive than high-end amateur equipment now on the market. But each boasts a wide field of view, roughly 60 times that of the full Moon. And that helps,...

The Question of Arecibo

by Paul Gilster | Nov 17, 2006 | Asteroid and Comet Deflection, Missions, Research Tools | 6 Comments

The recent National Science Foundation report recommending scaling back support for the Arecibo radio telescope raises eyebrows here. Arecibo has just been instrumental in identifying the near-Earth asteroid 1999 KW4 as a binary, one that provides useful information about the mass, shape and density of its components and hence about near-Earth asteroids in general. That's the kind of knowledge we need as we ponder how to analyze Earth-crossing objects to prevent future planetary disasters. But while focusing on ongoing radio astronomy work, the report gives short shrift to Arecibo's radar capabilities, which make this kind of investigation possible. In a letter to the NSF's Division of Astronomical Sciences, Guy Consolmagno SJ, who is head of the Department for Planetary Sciences of the American Astronomical Society, had this to say: There is in fact only one reference to radar in the entire 78 page document, and no mention at all of asteroids. But the Arecibo radar results are key...

Dark Energy News Multiplies

by Paul Gilster | Nov 17, 2006 | Deep Sky Astronomy & Telescopes, Exotic Physics | 2 Comments

Webster Cash's New Worlds concept, a starshade and telescope mission to directly image exoplanets, may not have received NASA Discovery funding this time around, but its creator isn't daunted. In a recent e-mail, Cash called the concept "...so robust that we aren't even viewing this as a setback. It's more of a lost opportunity." But Cash also provided an interesting speculation -- how about merging the starshade with the Joint Dark Energy Mission (JDEM)? Aimed at teasing out details about the mysterious repulsive force responsible for the universe's continuing acceleration, JDEM is in its research and development phase, with three mission concepts currently under scrutiny. All involve close study of Type 1a supernovae, objects whose known luminosity makes them ideal for measuring the universe's expansion. While we wait to see whether synergy develops between exoplanet imaging and JDEM, the dark energy news continues to come in. We learned a bit more yesterday, when NASA presented...

A Cosmic Ray Pinball Machine

by Paul Gilster | Nov 16, 2006 | Deep Sky Astronomy & Telescopes | 2 Comments

Following up on this morning's post re cosmic rays and the early Earth comes news that the Chandra X-ray Observatory has mapped cosmic ray acceleration in Cassiopeia A, a 325-year-old supernova remnant. The map, showing that electrons are being accelerated close to a theoretically maximum rate, provides evidence that supernova remnants are major contributors of energetic charged particles like cosmic rays. "Scientists have theorized since the 1960s that cosmic rays must be created in the tangle of magnetic fields at the shock, but here we can see this happening directly," said Michael Stage of the University of Massachusetts, Amherst. "Explaining where cosmic rays come from helps us to understand other mysterious phenomena in the high-energy universe." Image: This extraordinarily deep Chandra image shows Cassiopeia A (Cas A, for short), the youngest supernova remnant in the Milky Way. New analysis shows that this supernova remnant acts like a relativistic pinball machine by...

Early Life Shaped by Star Formation?

by Paul Gilster | Nov 16, 2006 | Astrobiology and SETI | 6 Comments

New work out of the Danish National Space Center (DNSC) suggests a startling connection between star-making in the Milky Way and the evolution of life on Earth. During a period of intense star-creation that began some 2.4 billion years ago, ocean-borne bacteria went through cycles of growth and decline of an intensity never since equalled. The Danish study links this variability with incoming cosmic rays that reach Earth from exploded stars. The star-making period in question was a time of numerous supernova explosions. To reach these conclusions, the Space Center's Henrik Svensmark studied the record of heavy carbon in sedimentary rocks. Growing bacteria and algae in ocean waters absorb carbon-12, leaving carbon-13 to enrich the sea; the latter begins to appear in the carbonate shells of sea creatures. By studying variations in carbon-13, Dr. Svensmark can see how much photosynthesis was going on when the shell-making species were alive. And it turns out that the biggest...

20 New Nearby Stars Discovered

by Paul Gilster | Nov 15, 2006 | Exoplanetary Science | 8 Comments

Watching the population of nearby stars grow is a chastening exercise. It reminds us that even in our own stellar neighborhood, there is much we have to learn. Consider that since the year 2000, the population of known stars within 10 parsecs (roughly 33 light years) of the Sun has grown by 16 percent. That includes 20 new stars identified recently by the Research Consortium on Nearby Stars (RECONS), whose list of the 100 nearest star systems can be found here. As you might have guessed, all twenty of the new objects are red dwarfs, and if you look throughout that 10-parsec volume, 239 of the 348 stars within it (other than our own star) are red dwarfs. That tallies nicely with earlier estimates that red dwarfs make up about 70 percent of the stars in the Milky Way, and points to the obvious fact that when you look up into the night sky, you're getting an unbalanced look at what's around us. None of the new stars are remotely visible with the naked eye. Image: The binary red dwarf...

Astrobiology Primer a Gem

by Paul Gilster | Nov 14, 2006 | Astrobiology and SETI | 1 Comment

Astrobiology, the study of life as a planetary phenomenon, aims to understand the fundamental nature of life on Earth and the possibility of life elsewhere. To achieve this goal, astrobiologists have initiated unprecedented communication among the disciplines of astronomy, biology, chemistry, and geology. Astrobiologists also use insights from information and systems theory to evaluate how those disciplines function and interact. The fundamental questions of what "life" means and how it arose have brought in broad philosophical concerns, while the practical limits of space exploration have meant that engineering plays an important role as well. So goes the introduction to the Astrobiology Primer now available as a reference tool for those trying to acquire the fundamentals of this multidisciplinary subject. Ninety researchers contributed insights and information to the collaborative effort. The work ranges through stellar formation and evolution, planet detection and characterization...

Minerals, Organics and Early Life

by Paul Gilster | Nov 14, 2006 | Astrobiology and SETI | 3 Comments

Where did our planet get the stuff from which life is made? The sources seem surprisingly diverse, and we're learning more about how organic materials may have complemented each other in forming life four billion years ago. Extraterrestrial compounds -- biomolecules formed in deep space and falling to Earth -- probably contributed. And so did lightning and ultraviolet radiation, along with vulcanism and deep water chemical reactions that could enhance molecular synthesis. Now getting new emphasis is the role of mineral surfaces in helping to activate molecules essential to life, like amino acids (from which proteins are made) and nucleic acids (think DNA). In a recent study, Robert Hazen (Carnegie Institution Geophysical Laboratory) described where we stand at identifying the pairing of molecule and mineral. When molecules like amino acids adhere to mineral surfaces, a variety of organic reactions can occur that affect what life can emerge. "Some 20 different amino acids form...

A Hunt for ET in Binary Systems?

by Paul Gilster | Nov 13, 2006 | Astrobiology and SETI | 6 Comments

An interesting story on Seth Shostak's recent appearances in Athens, OH ran today in The Athens News. In a pair of talks Shostak, senior astronomer for the SETI Institute (Mountain View, CA), explained to a general audience why he thinks extraterrestrial life is out there. He even gave a timeline for its discovery: within the next two dozen years (he went on to bet each member of the audience a cup of Starbuck's coffee on the proposition). Each SETI experiment, Shostak added, gathers more data than all the previous ones combined. Deep in the article are two Shostak suggestions for extending the SETI search. First, focus on the same area of sky for longer periods of time, instead of today's common practice of looking at a star for a few minutes and then moving on. Keep a longer gaze and look for signals of short duration that may repeat every few hours or days. The second tactic: work harder on binary systems. These may contain technological civilizations that have explored both sides...

A Boost for Optical Communications

by Paul Gilster | Nov 13, 2006 | Communications and Navigation | 0 Comments

Given how tricky it is to pick up accidental radio signals -- "leakage" -- from extraterrestrial civilizations, how hard would it be to communicate with our own probes once they've reached a system like Alpha Centauri? A front-runner for interstellar communications is the laser. JPL's James Lesh analyzed the problem in a 1996 paper, concluding that a 20-watt laser system with a 3-meter telescope as the transmitting aperture could beam back all necessary data to Earth. It's a system feasible right now. Right now, that is, if we had some way to get the telescope, just a bit larger than the Hubble instrument, into Centauri space. But even though propulsion lags well behind laser technology for such a mission, we're continuing to study how lasers can help closer to home. Their high frequencies allow far more data to be packed into the signal, but the highly focused beam also uses a fraction of the power of radio. Data return becomes less of a trickle and more of a flood (imagine...

SETI: Don’t Expect an Alien Sitcom

by Paul Gilster | Nov 11, 2006 | Astrobiology and SETI | 15 Comments

Since we've kicked around the idea of searching for SETI signals in the television bands (as noted in a previous story on Abraham Loeb and the Mileura Wide-Field Array), it's interesting to note Seth Shostak's thoughts on the subject. Because although planet Earth has been broadcasting TV signals for some time now, our transmissions are unlikely to be received at any great distance. And that makes a search for accidental TV-like emissions even from relatively nearby stars problematic. Shostak imagines a civilization 55 light years away hoping to pick up I Love Lucy from Earth. He notes that the non-directional TV signal, assuming a million watts of transmitter power, will reach this distant world "...with a power density of about 0.3 million million million million millionths of a watt per square meter..." And because only a third of the transmission power is in the carrier signal -- the most readily detected part of the transmission -- even that number is too high. It's possible to...

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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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