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101 Geysers on Enceladus (and What They Imply)

by Paul Gilster | Jul 31, 2014 | Uncategorized | 8 Comments

I've mentioned before the irony that we may discover signs of robust extraterrestrial life sooner around a distant exoplanet than right here in our own Solar System. The scenario isn't terribly implausible: Perhaps we come up empty on Mars, or find ourselves bogged down with ambiguous results. As our rovers dig, we still have Europa, Enceladus and other outer system possibilities, but probably face a wait of decades before we could build and fly the missions needed to identify life. Meanwhile, the exoplanet hunt continues. While we've had many a setback -- the Space Interferometry Mission will always stand out in this regard, not to mention the inability to follow through with Terrestrial Planet Finder, Darwin and other high-end concepts -- it's just possible that within the next few decades, a space-based observatory will detect a solid biosignature from an exoplanet's atmosphere. Even the James Webb Space Telescope should be able to detect the transmission spectrum of an...

HK Tauri: Misaligned Protoplanetary Disks

by Paul Gilster | Jul 30, 2014 | Exoplanetary Science | 15 Comments

When I was a boy in ninth grade, I asked our science teacher whether the nearest star was likely to have planets. He loved the question because it gave him the chance to explain to the class that Alpha Centauri was a binary star (we left poor Proxima out of the discussion), and that as a binary, it couldn't possibly have planets because their orbits would be too disrupted by gravitational effects to survive. That sounded reasonable to me, and I began putting my hopes on places like Tau Ceti and Epsilon Eridani, single stars with no disruptive companion. Since then we've begun finding binary stars with planets and are learning about the diversity of exoplanetary systems, putting Alpha Centauri back into the game. A good thing, too, given the fact that binary stars are common, and keeping them in the planet hunt allows that many more chances to find an Earth 2.0, not to mention all the other interesting kinds of planets including 'super-Earths' that we're locating. But the fact that...

‘Hot Jupiters’: Drier Than Expected

by Paul Gilster | Jul 29, 2014 | Exoplanetary Science | 18 Comments

Be aware of Open Source, a radio show on Boston's WBUR that last week did a show about exoplanets and the possibility of extraterrestrial life. Earth 2.0 is available online, featuring David Latham (Harvard-Smithsonian Center for Astrophysics), Dimitar Sasselov (Harvard University), Jason Wright (Penn State) and Sarah Rugheimer (a PhD student at Harvard studying exoplanet atmospheres). The discussion ranges through the Kepler mission to the Fermi question and recent studies of exoplanet atmospheres, the latter particularly appropriate to today's post. For I want to talk today about 'Hot Jupiters' and their atmospheres, and what we can learn about planet formation by studying their composition. Hot Jupiters were a surprise when first discovered, but models of planetary migration seemed to explain them. We would expect a gas giant to form at or beyond the 'snow line,' where volatiles like water would form ice grains. As we saw in our discussion of Kepler-421b (see Transiting World at...

Tight Measurement of Exoplanet Radius

by Paul Gilster | Jul 28, 2014 | Exoplanetary Science | 7 Comments

Both the Kepler and Spitzer space telescopes had a role to play in recent work on the planet Kepler-93b, whose size is now known to an uncertainty of a mere 120 kilometers on either side of the planet. What we have here is the most precise measurement of an exoplanet radius yet, a helpful result in the continuing study of 'super-Earths,' a kind of world for which we have no analogue in our own Solar System. A third instrument also comes into play, for studies of the planet's density derived from Keck Observatory data on its mass (about 3.8 times Earth's mass) and the known radius indicate this is likely an world made of iron and rock. And that is absolutely the only similarity between Kepler-93b and Earth, for at 0.053 AU, six times closer than Mercury to the Sun, the planet's surface temperature is estimated to be in the range of 760 degrees Celsius. The planet is 1.481 times the width of Earth. The accuracy of the measurement is the story here, a result so precise that, in the...

A Needle in the Cosmic Haystack: Formal and Empirical Approaches to Life in the Universe

by Paul Gilster | Jul 25, 2014 | Culture and Society | 59 Comments

Are we alone in the universe? Nick Nielsen muses on the nature of the question, for the answer seems to depend on what we mean by being 'alone.' Does a twin of Earth's ecosystem though without intelligent life suffice, or do we need a true peer civilization? For that matter, are we less alone if peer civilizations are widely spaced in time and space, so that we are unlikely ever to encounter evidence of them? And what of non-peer civilizations? SETI proceeds while we ponder these matters, a search that Nick sees as a priority because of the disproportionate value of an exterrestrial signal. Like Darwin in the Galapagos, we push on, collecting data in a quest that is without end. It's a prospect Nick finds invigorating, and so do I. by J. N. Nielsen One of the great questions of our time is, "Are we alone?" Even though it is, for us, an existential question that touches upon our cosmic loneliness, it is, at the same time, a scientific question, as befits our industrial-technological...

SETI: The Pollution Factor

by Paul Gilster | Jul 24, 2014 | Astrobiology and SETI | 39 Comments

We tend to assume that our mistakes as a species flag us as immature, a young civilization blundering about with tools it is misusing on a course that may lead to extinction. But assume for a moment that an intelligent extraterrestrial civilization goes through phases more or less like our own. If we're sifting through radio signals and looking for optical flashes to find them, shouldn't we consider other ways such a civilization announces itself? What if we're not the only polluters in the universe, for example, and other cultures are making the same mistakes? In a 2010 paper, Jean Schneider (Observatoire de Paris-Meudon) and colleagues noted the possibility of using pollutants as a way of moving beyond biosignatures to find ETI. Let me quote from the paper: ...another type of far from equilibrium signals can be seen as techno-signatures, i.e., spectral features not explained by complex organic chemistry, like laser emissions. In the present state of our knowledge one cannot...

Transiting World at the Snow Line

by Paul Gilster | Jul 23, 2014 | Exoplanetary Science | 9 Comments

It’s 9000 times easier to find a ‘hot Neptune’ than a Neptune out around the ‘snow line,’ that region marking the distance at which conditions are cold enough for ice grains to form in a solar system. Thus says David Kipping (Harvard-Smithsonian Center for Astrophysics), who is lead author on the paper announcing the discovery of Kepler-421b, an interesting world about which Kipping has been sending out provocative tweets this past week. Kepler-421b draws the eye because its year is 704 days, making it the longest orbital period transiting planet yet found. The intriguing new world is located about 1000 light years from Earth in the direction of the constellation Lyra. The transit method works by detecting the characteristic drop in brightness as a planet moves across the face of the star as seen from Earth. What’s unusual here is that Kepler-421b moved across its star only twice in the four years that the Kepler space telescope monitored it. As Kipping explains on this CfA web page,...

A Spacecraft in Your Pocket

by Paul Gilster | Jul 22, 2014 | Sail Concepts | 8 Comments

Last week we looked at Mason Peck's ideas on 'Sprites,' tiny spacecraft the size of computer chips that could be sent in swarms to targets near and far. I was particularly interested in Peck's idea of using Jupiter as a massive particle accelerator, bringing huge numbers of Sprites up to speeds in the range of hundreds of kilometers per second. Growing out of Clifford Singer's insights in the 1970s and given onboard intelligence by Gerald Nordley, the idea of 'smart pellets' thus moves beyond a propulsion method to become a fleet of networked space probes. Perhaps one day we'll be able to use the tools of nanotechnology to create highly intelligent vehicles of extremely small size, rendering the propulsion problem a bit more tractable. But until we're at that level, it's fascinating to see the groundwork being laid in work like Peck's. Today I want to talk about another experiment with space vehicles that are smaller than a compact disc and as thin as a piece of paper. Pocket...

First Words: Remembering July 20, 1969

by Paul Gilster | Jul 21, 2014 | Culture and Society | 20 Comments

I had hoped that the anniversary of the Apollo 11 landing would stir up some memories for Centauri Dreams regular Al Jackson, and I was not to be disappointed. Here, spurred partly by weekend news reports questioning who said the first words from the Moon, Al thinks back to a time of Champagne and jubilation, and gives us an inside look at those famous first words. He was also kind enough to pass along some of his own photos. A widely known figure in the interstellar community, Al was astronaut trainer on the Lunar Module Simulator and worked closely with, among many others, Neil Armstrong and Buzz Aldrin. He is also a man who never forgets a single thing he has ever read, as I learn every time I talk to him about science fiction, which I hope to do again this fall in Houston. by A. A. Jackson The 45th anniversary of the Apollo 11 landing was on a Sunday, just as it was on July 20 1969. My wife (of one year) and I lived in the Dijon Apartments in Clear Lake City, Houston. So for most...

Neil Armstrong: ‘A Little Bit of Bedlam’

by Paul Gilster | Jul 18, 2014 | Culture and Society | 27 Comments

As we approach the 45th anniversary of the first landing on the Moon, journalist and author Neil McAleer has been looking back at an interview he conducted with Neil Armstrong on March 16, 1989. The author of Visionary: The Odyssey of Sir Arthur C. Clarke (Clarke Project, 2012), McAleer has lived among and written about the space community for many years. We learn little about Clarke from this interview, but Armstrong's character comes through -- he's terse, focused, always impatient to get back to work. I suspect Centauri Dreams regular Al Jackson, who worked with Armstrong and Buzz Aldrin in his role as astronaut trainer on the Lunar Module Simulator (see The Magicians of Confidence), will recognize Armstrong's mode here immediately. His self-imposed distance could never conceal the cool competence he displayed on the most breathtaking descent in history. An interview conducted by Neil McAleer I requested this interview with Neil Armstrong 25 years ago, when I was writing and...

Sprites: A Chip-Sized Spacecraft Solution

by Paul Gilster | Jul 17, 2014 | Missions | 24 Comments

In mid-June, NASA announced the award of two contracts with Deep Space Industries in conjunction with the agency's plans to work with private industry in the exploration and harvesting of asteroids. One of these contracts caught my eye immediately. It involves small payloads that can ride along to supplement asteroid missions, and it's in the hands of NASA's former Chief Technologist, Mason Peck, a Cornell University aerospace engineer. Peck's work at Cornell's Space Systems Design Studio has led to the development of Sprites, fully functional spacecraft each weighing less than a penny. You can think of a Sprite as a spacecraft on a chip without any constraints from onboard fuel. You can see where this fits in with the current theme of building smaller spacecraft and sending them in swarms to investigate a particular target. You may have already run into KickSat, a citizen science project involving hundreds of proof-of-concept spacecraft in low Earth orbit for assessment of their...

‘Smart Pellets’ and Interstellar Propulsion

by Paul Gilster | Jul 16, 2014 | Sail Concepts | 15 Comments

When Clifford Singer proposed in his 1980 paper that a stream of pellets could be used to drive an interstellar vehicle, the idea emerged at a time when Robert Forward had already drawn attention to a different kind of beamed propulsion. Forward's sail missions used a beamed laser from an array near the Sun, and he explored the possibility of building a Fresnel lens in the outer Solar System to keep the beam tightly collimated; i.e., we want the narrowest possible beam to put maximum energy on the sail. It was an era when huge structures in space defined interstellar thinking. Forward's lasers were vast and he envisioned a 560,000-ton Fresnel lens in deep space, a structure fully one-third the diameter of the Moon. Such a lens made collimating the laser beam a workable proposition, to say the least -- at 4.3 light years, the distance of Alpha Centauri A and B, such a beam is still converging, and would not reach the size of its 1000 kilometer transmitting aperture until an amazing 44...

Clifford Singer: Propulsion by Pellet Stream

by Paul Gilster | Jul 15, 2014 | Sail Concepts | 12 Comments

Small payloads make sense if we can extract maximum value from them. But remember the problem posed by the rocket equation: It's not just the size of the payload that counts. A chemical rocket has to carry more and more propellant to carry the propellant it needs to carry more propellant, and so on, up the dizzying sequence of the equation until the kind of mission we're interested in -- deep space in reasonable time frames -- is ruled out. That's why other forms of rocket using fission or fusion make a difference. As the saying goes, they get more bang for the buck. But the idea of carrying little or no propellant at all has continued to intrigue the interstellar community, and numerous ways of doing so have been proposed. One early contender was a particle beam, which would be used to push a magnetic sail. Strip electrons from atomic nuclei and accelerate the positively charged particles close to the speed of light. There's a benefit here over laser-beamed sail concepts, for the...

Interstellar Journey: Shrinking the Probe

by Paul Gilster | Jul 14, 2014 | Autonomy and Robotics | 32 Comments

We've all imagined huge starships jammed with human crews, inspired by many a science fiction novel or movie. But a number of trends point in a different direction. As we look at what it would take to get even a robotic payload to another star, we confront the fact that tens of thousands of tons of spacecraft can deliver only the smallest of payloads. Lowering the mass requirement by miniaturizing and leaving propellant behind looks like a powerful option. Centauri Dreams regular Alex Tolley pointed to this trend in relation to The Planetary Society's LightSail-1 project. In a scant ten years, we have gone from the earlier Cosmos 1 sail with an area of 600 square meters to LightSail-1, with 32 square meters, but at no significant cost in scientific return because of continuing miniaturization of sensors and components. We can translate that readily into interstellar terms by thinking about future miniature craft that can be sent out swarm-style to reach their targets. Significant...

Exploring the Galaxy’s Outer Halo

by Paul Gilster | Jul 11, 2014 | Deep Sky Astronomy & Telescopes | 12 Comments

Not long ago we talked about what the Milky Way would look like when seen from afar. I had mentioned Poul Anderson's World Without Stars, which appeared in Analog in 1966 under the title The Ancient Gods. In the Anderson tale, a starship crew is sent to make contact with a recently discovered technological civilization that lives on a world hundreds of thousands of light years from the galactic core. Now a recent paper deepens our understanding of this environment deep in the galaxy's outer halo. Recall that the Milky Way is about 100,000 light years in diameter, and that the distance to the nearest large galaxy is roughly 2,500,000 light years. Anderson's crew is over 200,000 light years from the core, which puts them in the outer halo, a sparse spherical volume of space that stretches out 500,000 light years, well beyond the familiar, highly visible disk. While the stars in the galactic disk are on nearly circular orbits in the plane of the galaxy, the halo stars are on more...

Reflections on the LightSail Project

by Paul Gilster | Jul 10, 2014 | Sail Concepts | 33 Comments

I was delighted to see Doug Stetson, the program manager for The Planetary Society's LightSail effort, quoting Johannes Kepler in last night's webcast. If you missed the Pasadena event, which took place at the KPCC Crawford Family Forum in Pasadena, CA, you can watch the recorded session here, and I highly recommend it. Kepler's 1610 letter to Galileo added context to the excitement over LightSail, for solar sailing has a rich history. Kepler wrote of providing "ships or sails adapted to the heavenly breezes," and added that "there will be some who will brave even that void." It's an inspiring thought as we now look into the launch of a privately funded sail that can join IKAROS and NanoSail-D in a series of operational experiments that will hone our sail knowledge. The chief news of the Pasadena meeting was the announcement of an approximate launch date. LightSail-1 is scheduled to go into space aboard a SpaceX Falcon Heavy rocket in April of 2016. The quick video Mat Kaplan showed...

Focus on LightSail-A

by Paul Gilster | Jul 9, 2014 | Sail Concepts | 7 Comments

As Cosmos 1 demonstrated, launching solar sails isn't always easy. The Planetary Society's sail perished thanks to a malfunctioning Volna booster not long after launch in 2005. When NASA attempted to launch its NanoSail-D in 2008, a problem aboard the Falcon 1 booster destroyed the craft. And when the agency launched the backup, NanoSail-D2, in December of 2010, the CubeSat-based sail failed to eject from the FASTSAT satellite it was aboard. Just when all seemed lost, NanoSail-D2 ejected on its own on January 17, 2011 and deployed its sail soon after. Now we're looking at a new Planetary Society venture called LightSail-A, which grows out of the NanoSail-D project and, according to news that should be firmed up tonight, should be ready for launch in the near future. As with Cosmos 1, the funding for LightSail-A was raised from private sources and Planetary Society membership dues, with the spacecraft itself being built by Stellar Exploration Inc. out of San Luis Obispo, CA. With...

Cosmos 1 in Context

by Paul Gilster | Jul 8, 2014 | Sail Concepts | 4 Comments

We're coming up on the tenth anniversary of Centauri Dreams, and it doesn't surprise me even remotely that two of the earliest stories I ever wrote for the site involve solar sails. August 17, 2004's Solar Sail Test by Japan talks about the Japanese Institute of Space Astronautical Science testing sail deployment strategies, and the August 14 entry, Cosmos 1 Solar Sail Closer to Launch, briefly describes the privately funded sail that was developed by The Planetary Society's efforts, with financial contributions from members and major backing from Ann Druyan's Cosmos Studios. I've been fascinated with space sailing since first encountering the notion in 1960s-era science fiction, particularly Clarke's "The Wind from the Sun" and Cordwainer Smith's "The Lady Who Sailed the Soul." What I lacked back then, though, was an appreciation for the challenge posed by the rocket equation, which demands so much more propellant the faster you want to go. Space missions demand huge mass ratios...

Sailing to Halley’s Comet

by Paul Gilster | Jul 7, 2014 | Sail Concepts | 4 Comments

We have interesting solar sail news coming up later this week, so it seems a good time to lead into it with some thoughts on NASA's early solar sail work. For the theoretical work for a sail rendezvous with Halley's Comet was well along in the 1970s, when Louis Friedman, later a founder and executive director of The Planetary Society, led what would become the first space agency attempt to develop an actual sail mission. Friedman's interest in and commitment to sail ideas will become apparent as this week progresses and we look at other sail designs. Much of the impetus for a NASA sail study in the 1970s -- a $4 million effort at the Jet Propulsion Laboratory in 1977 and 1978 -- can be traced back to Jerome Wright, an engineer at the Battelle Memorial Institute in Ohio. In his book Starsailing: Solar Sails and Interstellar Travel (John Wiley & Sons,1988), Friedman recalls a meeting of the Advanced Projects Group at the Jet Propulsion Laboratory in which he learned about Wright's...

A Manifesto for Expansion

by Paul Gilster | Jul 4, 2014 | Culture and Society | 34 Comments

Michael Michaud gave the speech that follows in 1988 at the 39th International Astronautical Congress, which met in Bangalore, India in October of that year. Reading through it recently, I was struck by how timely its theme of spaceflight advocacy and human expansion into the cosmos remains today. When he wrote this, Michaud was director of the Office of Advanced Technology for the US Department of State, though he reminded his audience that the views herein were his own and not necessarily those of the US government. Michaud's support of spaceflight and his determinedly long-term approach to our possibilities as a species has distinguished his space writing, which has been prolific and includes the essential Contact with Alien Civilizations (Copernicus, 2006). Although I had thought of updating some of the references below, it seems unnecessary. What counts are the themes. Working well before the recent surge in interstellar interest, Michael here explains why humans need to develop...

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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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