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A Circumbinary Planetary System

by Paul Gilster | Aug 30, 2012 | Exoplanetary Science | 23 Comments

Among the more interesting items coming out of the XXVIII General Assembly of the International Astronomical Union (IAU) in Beijing is news of a circumbinary system containing two planets. We've seen circumbinary worlds before -- Kepler-16b is a planet orbiting not one but two stars, as are Kepler-34b and Kepler-35b. There was a time that the idea of a planet orbiting two stars, as opposed to orbiting one or the other of two stars in a binary system, seemed unlikely. Now we have a multiple-planet system in exactly this configuration. It's an interesting one, too. Some 4900 light years from Earth in the constellation Cygnus, the two stars orbit each other roughly every 7.5 days. One of the stars is fairly similar to the Sun, though about 15 percent less bright, while the other is an M-dwarf about a third of Sol's size and 175 times fainter. Of the two planets, one -- Kepler-47b -- is three times the diameter of Earth and eight times its mass, orbiting the twin stars every 49 days. The...

Remembering the Early Robotic Explorers

by Paul Gilster | Aug 29, 2012 | Autonomy and Robotics | 37 Comments

Reflecting back on the history of robotic space missions, Larry Klaes offers a look at the early missions to Venus and Mars, harbingers of the far more complex probes we would later send into the Solar System. The Pioneers, Veneras and Mariners were, in their day, on the forefront of planetary research, blazing the trail most recently followed by Curiosity on Mars. As a site focused on deep space issues, we often return to Voyager and Pioneer, but let's not forget how planetary exploration got its start. By Larry Klaes Once upon a time, our Solar System was a very lively place. In past centuries, most if not all of the known planets and their moons, along with the even smaller members of our celestial neighborhood, were imagined to have native life forms as numerous and diverse as those found on Earth. Otherwise, it seemed pointless for whole worlds to exist without any inhabitants. Then along came the Twentieth Century. Improved knowledge about the Sol system caused the majority of...

The Magicians of Confidence

by Paul Gilster | Aug 28, 2012 | Culture and Society | 12 Comments

Centauri Dreams regular Al Jackson responded to yesterday's post about Neil Armstrong with reminiscences of the Apollo program, but because the first of these ran as a comment to the story, I was afraid a lot of readers wouldn't see it -- we have far more subscribers through RSS than any other medium, and many of them do not see the comments. When Al submitted a second comment, I decided to merge them into a single post here. The author of numerous scientific papers and a widely known figure in the interstellar community, Al saw the Apollo program up close as astronaut trainer on the Lunar Module Simulator. Here he talks about Armstrong and Aldrin and the antics of the crew that followed Apollo 11. by A. A. Jackson I spent almost 4 years in the presence of Neil Armstrong and Buzz Aldrin. I came to the Manned Spacecraft Center (MSC) in 1966, where I was placed as a crew training instructor. I had degrees in math and physics at that time. Seems engineers were pressed into real...

On Neil Armstrong

by Paul Gilster | Aug 27, 2012 | Culture and Society | 49 Comments

"Neil Armstrong may well be the only human being of our time to be remembered 50,000 years from now." -- J. G. Ballard, "Back to the Heady Future," Daily Telegraph, 17 April 1993. If anything, Neil Armstrong was almost too perfect for the role he played. If I had been asked to script the kind of character I'd like to have seen as the first man on the Moon, Armstrong would have walked into the role effortlessly, a quiet, even diffident man who had the courage to ride rockets. Flyers come in all descriptions, but those I used to hang around with in my own flying days (far tamer than any of Armstrong's, to be sure!) were generally raconteurs, full of improbable tales that could never be verified, jongleurs seasoned in the arts of extroversion. Not so Neil Armstrong, and therein lies the reason for my own sense of pride in the man and his accomplishment. July 20, 1969 was, inevitably, a hot day in St. Louis. I had driven to Webster Groves that afternoon to watch the moon landing with my...

Magellanic Clouds a Celestial Rarity

by Paul Gilster | Aug 24, 2012 | Deep Sky Astronomy & Telescopes | 13 Comments

The Magellanic Clouds, visible in the southern hemisphere, are two dwarf galaxies that orbit the Milky Way, a fact that has always captivated me. We see the galaxy from the inside, but I have always wondered what it would be like to see it from the perspective of the Magellanics. The Large Magellanic Cloud (LMC) is, after all, only 160,000 light years out, while the Small Magellanic (SMC), its companion cloud, is about 200,000 light years away. Add in the recently discovered Sagittarius Dwarf Elliptical at 50,000 light years from the galactic core and you have three exotic venues from which to gain a visual perspective on the Milky Way, at least in the imagination. We’re so used to thinking that our solar and galactic neighborhoods are utterly commonplace that it may come as a surprise to learn that the configuration of spiral galaxy and satellite galaxies that we see in the Milky Way is actually quite unusual. New work on this comes from Aaron Robotham (International Center for...

A Planet Engulfed by a Red Giant?

by Paul Gilster | Aug 23, 2012 | Exoplanetary Science | 19 Comments

Polish astronomer Aleksander Wolszczan (Penn State) is best known as the discoverer of the first confirmed planet outside our Solar System. That was back in the early 1990s, when Wolszczan was working with Dale Frail (NRAO), using observations from the Arecibo dish to demonstrate that the pulsar PSR B1257+12 was orbited by two planets. These are relatively small worlds (3.9 and 4.3 Earth masses respectively), and in an era where new planet candidates number in the thousands, it’s easy to forget how striking Wolszczan’s work appeared at the time, and how it gave impetus to the developing exoplanet hunt. A pulsar planet looks to be an extremely inhospitable place, but learning how planets are distributed among the stars involves studying every conceivable kind of world. Wolszczan’s latest work targets an equally hostile environment, the former habitable zone of a star that has begun expanding into a red giant. The star, BD+48 740, has 11 times the Sun’s radius and is significantly...

Exotic Detections: Wormholes and Worldships

by Paul Gilster | Aug 22, 2012 | Exotic Physics | 255 Comments

SETI always makes us ask what human-centered assumptions we are making about extraterrestrial civilizations. When it comes to detecting an actual technology, like the starships we've been talking about in the last two posts, we've largely been forced to study concepts that fit our understanding of physics. Thus Robert Zubrin talks about how we might detect a magsail, or an antimatter engine, or a fusion-powered spacecraft, but he's careful to note that the kind of concepts once studied by the Breakthrough Propulsion Physics Project at NASA may be undetectable, since we really don't know what's possible and what its signature might be. I mentioned zero-point energy in a previous post because Zubrin likewise mentions it, an idea that would draw from the energy of the vacuum at the quantum level. Would a craft using such energies -- if it's even possible -- leave a detectable signal? I've never seen a paper on this, but it's true that one classic paper has looked at another truly exotic...

SETI: Starship Radiation Signatures

by Paul Gilster | Aug 21, 2012 | Uncategorized | 14 Comments

Yesterday we pondered the possibility of detecting an interstellar craft as a new kind of SETI. If the energies needed to drive such a vessel are as titanic as we think, there could be a detectable signature, as Robert Zubrin pointed out in a 1995 paper. Zubrin's best case in visible light involved an antimatter engine whose exhaust could be detected from as far as 300 light years from Earth. That would cover a huge number of stars, as 100,000 exist within 200 light years of our planet. I suppose the classic starship detection occurs in Larry Niven and Jerry Pournelle's 1975 novel The Mote in God's Eye, where human starfarers using the 'Alderson Drive' -- which allows instantaneous jumps between stars -- detect an alien, laser-pushed lightsail. The starship is a throwback, an older technology that human interstellar methods have long superseded, one that contains a strange, asymmetric alien being, the first extraterrestrial humans have encountered. It's no surprise to learn that...

To Detect a Starship

by Paul Gilster | Aug 20, 2012 | Astrobiology and SETI | 42 Comments

Several Centauri Dreams readers passed along Seth Shostak's latest article on SETI in IEEE Spectrum, a piece that invokes the 'Wow!' signal at Ohio State and goes on to make the case for continuing the hunt. Shostak thinks both the ongoing search for exoplanets and refinements in our signal detection technology, including optical SETI, should keep us active. "No, we haven't found any signals so far, but there's a growing incentive provided by new findings in astronomy and biology, and the instruments are getting better," he writes. "Thirty-five years from now, we may really find a signal that will make us say 'Wow!'" The IEEE Spectrum piece doesn't break any new ground, but it's another example of the 'Wow!' signal getting broader coverage, and I now find that people routinely bring the Ohio State event up when I talk to audiences about SETI. Meanwhile, let's think about some truly exotic possibilities when it comes to detecting extraterrestrial life. Would it be possible, for...

Are ‘Waterworlds’ Planets in Transition?

by Paul Gilster | Aug 17, 2012 | Exoplanetary Science | 48 Comments

Ponder how our planet got its water. The current view is that objects beyond the 'snow line,' where water ice is available in the protoplanetary disk, were eventually pushed into highly eccentric orbits by their encounters with massive young planets like Jupiter. Eventually some of these water-bearing objects would have impacted the Earth. The same analysis works for exoplanetary systems, but the amount of water delivered to a potentially habitable planet depends, in this scenario, on the presence of giant planets and their orbits. Dorian Abbot (University of Chicago) and colleagues Nicolas Cowan and Fred Ciesla (both at Northwestern University) note the consequences of this theory of water delivery. One is that because low mass stars are thought to have low mass disks, they would have fewer gas giants and would produce less gravitational scattering. In other words, we may find that small planets around M-dwarfs are dry. On the other hand, solar-mass stars and above could easily have...

Barnard’s Star: No Sign of Planets

by Paul Gilster | Aug 16, 2012 | Exoplanetary Science | 24 Comments

Barnard's Star has always gotten its share of attention, and deservedly so. It was in 1916 that this M-class dwarf in Ophiuchus was measured by the American astronomer Edward Emerson Barnard, who found its proper motion to be the largest of any star relative to the Sun. That meant the star soon to be named for him was close to us, and unless we're surprised by a hitherto unobserved brown dwarf, Barnard's Star remains the closest star to our Sun after the Alpha Centauri triple system. Stick around long enough and Barnard's Star will close to within 3.75 light years, but even if you make it to 10,000 AD or so, the star will still be too faint to be a naked eye object. Image: Barnard's Star, with proper motion demonstrated, part of an ongoing project to track the star. This image shows motion between 2004 and 2008. Credit: Paul Mortfield & Stefano Cancelli/The Backyard Astronomer. Peter van de Kamp, working at Swarthmore College, had been looking for wobbles in the position of Barnard's...

100 Year Starship Public Symposium

by Paul Gilster | Aug 15, 2012 | Culture and Society | 5 Comments

"The future never just happened, it was created." The quote is from Will and Ariel Durant, the husband and wife team who collaborated on an eleven-volume history of civilization that always used to be included in Book of the Month deals, which is how many of us got our copies. I'm glad to see the Durants' quotation brought into play by the 100 Year Starship organization in the service of energizing space exploration. It's a call to create, to work, to push our ideas. 100 Year Starship (100YSS) puts the Durants' thinking into practice at the second 100 Year Starship Public Symposium, September 13-16 at the Hyatt Regency in Houston. The event promises academic presentations, science fiction panels, workshops, classes and networking possibilities for those in the aerospace community and the public at large. My hope is that the gathering will kindle some of the same enthusiasm we saw last October in Orlando, when the grant from DARPA that created the 100 Year Starship had yet to be...

Starships: ‘Skylark’ vs. the Long Haul

by Paul Gilster | Aug 14, 2012 | Culture and Society | 59 Comments

Centauri Dreams readers will remember Adam Frank's recent op-ed Alone in the Void in the New York Times arguing that given the difficulty involved in traveling to the stars, humans had better get used to living on and improving this planet. 'We will have no other choice,' wrote Frank. 'There will be nowhere else to go for a very long time.' I responded to Frank's essay in Defending the Interstellar Vision, to which Frank replied on his NPR blog. Dr. Frank is an astrophysicist at the University of Rochester and author of the highly regarded About Time: Cosmology and Culture at the Twilight of the Big Bang (Free Press, 2011), a study of our changing conception of time that is now nearing the top of my reading stack. In his short NPR post, he makes a compelling point: Even if we could get a starship up to 10% of light speed (which would be an epoch-making achievement) then the round trip to the nearest known star with a planet would still take 300 years (it's Gliese 876d for all you...

Into the Uncanny Valley

by Paul Gilster | Aug 13, 2012 | Culture and Society | 29 Comments

After our recent exchange of ideas on SETI, Michael Chorost went out and read the Strugatsky brothers' novel Roadside Picnic, a book I had cited as an example of contact with extraterrestrials that turns out to be enigmatic and far beyond the human understanding. I've enjoyed the back and forth with Michael between Centauri Dreams and his World Wide Mind blog because I learn something new from him each time. In his latest post, Michael explains why incomprehensible technology isn't really his thing. A Sense of the Weird Why? Michael grants the possibility that extraterrestrial intelligence may be far beyond our understanding. But in terms of science fiction and speculation in general, he favors what he calls 'the uncanny valley,' the sense of weirdness we get from a technology that is halfway between the incomprehensible and the known. A case in point is Piers Anthony's novel Macroscope, in which an alien message overwhelms the minds of those who can understand it (people with IQs in...

‘Deep Space Propulsion’: A Review

by Paul Gilster | Aug 10, 2012 | Culture and Society | 52 Comments

What I have in mind today is a book review, but I'll start with a bit of news. The word from Houston is that Ad Astra Rocket Co., which has been developing the VASIMR concept from its headquarters not far from Johnson Space Center in Texas, has been making progress with its 200-kw plasma rocket engine prototype. VASIMR (Variable Specific Impulse Magnetoplasma Rocket) offers constant power throttling (CPT), which would allow it to vary its exhaust for thrust and specific impulse while maintaining a constant power level. CPT has now been demonstrated in a June test, as was reported at the recent AIAA Joint Propulsion Conference in Atlanta and in trade publications like Aviation Week, a useful step forward for the program. VASIMR in Deep Space What to make of VASIMR's chances? When assessing something like this, I turn to my reference library, and because I've recently been reading Kelvin Long's Deep Space Propulsion, I wanted to see what he said about VASIMR. Long treats the subject in...

Hit by a Falling Star

by Paul Gilster | Aug 9, 2012 | Asteroid and Comet Deflection | 27 Comments

About a year ago a French couple by the name of Comette returned to their home to find that a meteorite had struck their house while they were away on holiday. It could be said that the Comettes already had a celestial connection -- if in name only -- but now the heavens impinged upon their lives again, a fact they didn't realize until their roof began to leak. Living in Draveil, about 12 miles south of Paris, the couple discovered that the space rock had blown right through a thick tile and wedged itself in glass wool insulation. It turns out to be an iron-rich chondrite some 4.57 billion years old. France, according to this article in The Telegraph, receives the highest number of meteorites per capita in the world, and the Comettes have no intention of parting with this one. The story reminded me of 14-year old Gerrit Blank, who was hit on the hand by a red-hot piece of rock about the size of a pea that went on to create a foot-wide crater in the ground. This was back in 2009 in...

SETI: Contact and Enigma

by Paul Gilster | Aug 8, 2012 | Astrobiology and SETI | 45 Comments

I'm not surprised that Michael Chorost continues to stimulate and enliven the SETI discussion. In his most recent book World Wide Mind (Free Press, 2011), Michael looked at the coming interface between humans and machines that will take us into an enriched world, one where implants both biological and digital will enhance our experience of ourselves and each other. You'll recall that it was a cochlear implant that restored hearing to this author, and doubtless propelled the thinking that led to this latest book. And it was the issue of hearing and communication that we looked at in an earlier discussion of Chorost's views on SETI. That conversation has continued in Michael's World Wide Mind blog, as he ponders some of the comments his earlier ideas provoked on Centauri Dreams. In particular, how would we ever come to understand an extraterrestrial civilization if it differed fundamentally from us? Chorost thinks the problem is not biological, that no matter how aliens might look, we...

Voyager Update: Still in Choppy Waters

by Paul Gilster | Aug 7, 2012 | Missions | 8 Comments

The continued explorations of our two Voyagers have earned these tough spacecraft the right to be considered an interstellar mission, which is how NASA now describes their journeys. Neither will come anywhere near another star for tens of thousands of years, but in this context 'interstellar' means putting a payload with data return into true interstellar space. Right now the Voyagers are still within the heliosphere, that great bubble opened out around our system by the Sun's solar wind, and the signs are multiplying that a transition is soon to occur. Three measurements are going to mark the boundary crossing, and we're seeing that two out of the three are in a state of rapid change. This JPL news release points out that on July 28, Voyager 1's cosmic ray instrument showed a jump of five percent in the level of galactic cosmic rays the craft was encountering. In the second half of that same day, the level of lower-energy particles flowing from inside the Solar System dropped by...

After Curiosity (whew!), Thoughts on Enceladus

by Paul Gilster | Aug 6, 2012 | Outer Solar System | 20 Comments

At $2.5 billion, NASA's Curiosity rover didn't cost quite as much as Cassini ($3 billion), but what a relief to Solar System exploration both near and far to have it safely down at Gale Crater. This Reuters story tells me that 79 different pyrotechnic detonations were needed to release ballast weights, open the parachute, separate the heat shield, detach the craft's back shell and perform the rest of the functions needed to make this hair-raising landing a success. All of this with a 14-minute round-trip radio delay that left mission engineers as no more than bystanders. Congratulations to the entire Curiosity team on this triumphant event! As we now move into the next several weeks checking the six-wheeled rover and its instruments out for exploration, let's ponder future targets beyond the Red Planet. For at some point, no matter what we find on Mars, we're going to want to push on to the outer planets, where intriguing moons like Titan, Europa and Enceladus await. The latter's...

Habitable Worlds More Like Our Own

by Paul Gilster | Aug 3, 2012 | Exoplanetary Science | 35 Comments

Gliese 581 is an utterly maddening star, one that continues to tantalize us with potential habitability. The case of Gl 581g, examined here yesterday, is only the latest wrinkle, but it's in some ways the most frustrating. We're studying planets we cannot actually see, inferring their presence through the tiniest of variations in starlight caused by the planets' gravitational effect on their star. Adjust planetary orbits here in the direction of eccentricity and you can make Gl 581g disappear. Assume circular orbits and you can produce a habitable zone super-Earth. I think we'll still be arguing about this one for some time, but in the interim the question will lose a lot of its force. Remember, the reason we're so excited about Gl 581g is that it would become the closest planet with the possibility of liquid water at the surface (possibly joined by Gl 581d in the same system). But Jean Schneider's Exoplanet.eu catalog shows 777 confirmed planets this morning, and Kepler has pulled...

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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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