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MEarth: Searching for Habitable ‘Super-Earths’

by Paul Gilster | Feb 13, 2009 | Exoplanetary Science | 7 Comments

Will the first 'super-Earth' in the habitable zone of its star be found around a red dwarf? An M5-dwarf with both mass and radius about a quarter that of the Sun would have 1/200th Sol's luminosity. That's interesting for transit purposes, for a planet in the habitable zone around this star would be close in indeed, some 0.074 AU out, with an orbital period of 14.8 days. Its transit probability would correspondingly be raised by a factor of three compared to the Earth-Sun system. The result, as laid out by the transit survey called MEarth: Detecting such planets should be possible from the ground. Take a look at the live video of what MEarth is doing. Based at the Fred Lawrence Whipple Observatory on Mt. Hopkins in Arizona, the team works with 1976 nearby red dwarfs, visiting each repeatedly in hopes of snaring an ongoing transit, whose information would then be routed to larger instruments for confirmation. They're looking at targets spread over the entire celestial northern...

Deep Questions About an Impact

by Paul Gilster | Feb 12, 2009 | Asteroid and Comet Deflection | 6 Comments

Things move around in the story queue here, but occasionally a particular item almost gets past me before I remember to cover it. Such is the recent work on the possible impact event some 12,900 years ago, which Richard Firestone (Lawrence Berkeley Laboratory) and colleagues have argued would have contributed to the extinction of such large mammals as woolly mammoths and mastodons, not to mention causing continent-wide wildfires that could have brought about the end of the Clovis culture in North America. The period in question comes at the beginning of the Younger Dryas, a 1300-year cold spell whose termination saw the temperature of Greenland warm by over 5°C in just a few decades (see comments below). We've speculated about the possibility of an asteroid or comet impact on Centauri Dreams (the most recent story is here), but new analysis casts doubt on the theory. Sandy Harrison (University of Bristol) has gone to work on charcoal and pollen evidence to study how wildfires...

Interstellar Strategy: Spreading the Word

by Paul Gilster | Feb 11, 2009 | Culture and Society | 3 Comments

by Tibor Pacher My friend Tibor Pacher is joined with me (until 2025, anyway) in our 'interstellar bet,' under the auspices of the Long Now Foundation. Trained as a physicist at the Eötvös University in Budapest and the University of Heidelberg, Dr. Pacher has been exploring ways to get across interstellar concepts to the public through venues like his peregrinus interstellar. Social networking is to some of us a new frontier, and I've asked Tibor to provide some background on what he is doing to make sure that an obscure wager develops an audience and becomes an effective teaching tool. Yesterday I watched the movie In the Shadow of the Moon. I must admit, this was not the first time, but I wanted to capture more details and - well, it is just a great film, and, I believe, not only for space heads a 'must.' Sober and emotional at the same time, for me it is a perfect example of how the public imagination can be captured about space, in a way which shows the deeply human nature of...

361 Civilizations in the Galaxy?

by Paul Gilster | Feb 10, 2009 | Astrobiology and SETI | 26 Comments

I promised a quick return to recent work on the Drake Equation, which helps us estimate the number of communicating civilizations in the galaxy, but a BBC story on Duncan Forgan has me back at it even sooner than I had intended. It's no surprise that the matters encapsulated in Drake's thinking should be in the news. After all, the era of Fermi and Drake was without firm knowledge of extrasolar worlds, of which we now know over three hundred. For that matter, the concepts of habitable zones around both stars and the galaxy itself had not come to fruition, nor had anyone ever heard of the 'rare Earth' hypothesis. We also work today with knowledge of Charles Lineweaver's studies of the median age of terrestrial planets in the Milky Way, which point to civilizations around other stars having had as much as two billion years-plus to emerge before our own Earth had even coalesced. Until we know more, I suspect we'll be adjusting Drake parameters for some time, as Duncan Forgan (University...

Dust Up Between the Stars

by Paul Gilster | Feb 9, 2009 | Interstellar Medium | 20 Comments

Almost four years ago I wrote a Centauri Dreams entry about Dana Andrews' views on shielding an interstellar spaceship. The paper is so directly relevant to our recent discussion on the matter that I want to return to it here. Andrews (Andrews Space, Seattle) believes that speeds of 0.2 to 0.3 c are attainable using beamed momentum propulsion. That being the case, he turns in his "Things to Do While Coasting Through Interstellar Space" paper to questions of human survival. Particles with a Punch Collision with interstellar dust becomes a major issue when you're traveling at speeds like these, a fact Andrews is quick to quantify. For a starship moving at 0.3 c, a typical grain of carbonaceous dust about a tenth of a micron in diameter should have a relative kinetic energy of 37,500,000 GeV. Our hypothetical star mission with human crew moving at a substantial fraction of light speed will run into about thirteen of these dust particles every second over every square meter of frontal...

Dissent on Drake

by Paul Gilster | Feb 7, 2009 | Astrobiology and SETI | 30 Comments

Centauri Dreams' recent post on the Drake Equation triggered a broad range of response, both in comments and back-channel e-mails, the latter of which produced a note from Kelvin Long quoting a rather controversial position on Drake by one leading scientist. Here it is. See if it raises your hackles: "I reject as worthless all attempts to calculate from theoretical principles the frequency of occurrence of intelligent life forms in the universe. Our ignorance of the chemical processes by which life arose on earth makes such calculations meaningless." The words are Freeman Dyson's, from his essay "Extraterrestrials" in Disturbing the Universe (Harper & Row, 1979), a book I re-read every few years as much to admire the author's rhetorical skills as to draw again on his insights. Kelvin has differing views on Drake and so do I, but I'm going to quote Marc Millis' reaction to the Dyson statement, reflecting as it does an approach toward scientific method that I share. Marc writes: "On...

Interstellar Flight: The Dust Conundrum

by Paul Gilster | Feb 6, 2009 | Interstellar Medium | 11 Comments

It would be helpful if space were a bit more empty. A key problem facing an interstellar probe would be encounters with dust in the planetary system it leaves and, as it reaches cruising speed, dust impact in space between the stars. Although our Solar System seems to be in an unusually sparse pocket of space, the galaxy-wide distribution of hydrogen is roughly one atom per cubic centimeter. Dust -- bits of carbon, ice, iron compounds, and silicates -- is far rarer still, but enough of a factor to a ship moving at a significant fraction of the speed of light that the designers of the Project Daedalus craft built in a payload shield 32-meters in radius to protect their starship. Then again, much depends on your location. Have a look at the image below. It's an area called the Red Rectangle some 2300 light years from Earth in the constellation Monoceros. Although the center of the image seems to be a single star, it's actually the double star system HD 44179. The Red Rectangle is a...

Tightening the Asteroid Focus

by Paul Gilster | Feb 5, 2009 | Outer Solar System | 3 Comments

Asteroid (234) Barbara is an unusual object, a denizen of the main belt that may be a binary. The European Southern Observatory's Very Large Telescope Interferometer is able to piece together two bodies, with diameters of 37 and 21 kilometers respectively, separated by a bit over 20 kilometers. But as seen from Earth, the objects seem to overlap, so we don't know whether this is a true binary or an asteroid in the shape of a giant peanut. The former would be more interesting, for if we can calculate the orbits of these objects and combine them with diameter measurements, we'll learn about their density. This is why Sebastiano Ligori (INAF-Torino, Italy) calls Barbara "...a high priority target for further observations." Ligori is one of the researchers who used the combined light from two of the Very Large Telescope's 8.2-meter instruments to make these interferometric studies, creating a view as sharp as a single telescope whose diameter is as large as the separation between the...

COROT Finds a Small, Rocky World

by Paul Gilster | Feb 4, 2009 | Exoplanetary Science | 16 Comments

The COROT mission's 27-cm telescope has discovered the smallest exoplanet yet, with a diameter less than twice that of Earth. COROT-Exo-7b orbits a Sun-like star and highlights the ongoing space-based investigation into rocky worlds that is drawing ever closer to an Earth-mass object. This is the kind of work COROT was designed to do, flagging planetary transits across the face of a star from an orbital perch that allows long periods of uninterrupted observation and the chance to measure the size of the planets found. ESA's Malcolm Fridlund discusses the significance of the find: "This discovery is a very important step on the road to understanding the formation and evolution of our planet. For the first time, we have unambiguously detected a planet that is 'rocky' in the same sense as our own Earth. We now have to understand this object further to put it into context, and continue our search for smaller, more Earth-like objects with COROT." Finding a 'super-Earth' is one thing when...

New Angles on the Drake Equation

by Paul Gilster | Feb 3, 2009 | Astrobiology and SETI | 15 Comments

The Drake Equation in its various forms has been tormenting us for decades, raising the question of how to adjust variables that range from astronomical (the abundance of terrestrial planets) to biological (the probability of life's emergence) and even sociological (the average lifetime of a technological civilization). Wildly optimistic estimates of the number of technological civilizations in our galaxy are now giving way to more sober reflection. Now Reginald Smith (Bouchet-Franklin Institute, Rochester NY) offers up a new analysis looking at how likely radio contact is given a civilization's lifetime, and how widely that civilization's signals can be clearly received. The key question: What if there is a reasonable horizon for the detection of a signal from an extraterrestrial sender? Signals and Their Lifetime This is useful stuff, because contact depends not just upon the density of communicating civilizations (CC) but their average lifetime and the maximum detectable distance...

Interstellar Studies: Building the Base

by Paul Gilster | Feb 2, 2009 | Culture and Society | 9 Comments

With the Kepler mission scheduled for launch this spring, we should see increasing attention in the media on the detection of terrestrial-class exoplanets and speculations on possible life upon them. But it's easy to forget that Kepler has other important goals, taking estimates, for example, on the disposition of planets in multiple star systems, and studying the stars that have planets in orbit around them. Kepler will also be looking at planetary distribution, including 'hot Jupiters,' and examining their size, density and reflectivity. A Deep Space Challenge for Bloggers All of which is a tall order for a three and a half-year mission, but we can expect a successful run to result in an extended mission as Kepler keeps its gaze fixed on a region in space allowing it to monitor the brightness of more than 100,000 stars. Have a look at OrbitalHub's treatment of Kepler in the current Carnival of Space, where DJ runs through the mission parameters and examines the equipment. Looking...

Titan: A Rainy Season Ahead?

by Paul Gilster | Jan 30, 2009 | Outer Solar System | 6 Comments

Rain seems to have been plentiful at Titan's south pole. A new analysis of Cassini imagery compares the region in recent times with what it was about a year earlier, noting new features in areas many scientists believe to be lakes of liquid hydrocarbons. Adding to the conjecture is the fact that extensive cloud systems covered the region during this period, evidence for a large rainstorm amid changing seasons. All this comes from the almost global surface map Cassini's Imaging Science Subsystem has been acquiring since April of 2004. Have a look at some of this imagery, and keep an eye in particular on Ontario Lacus, at the bottom of each image, noting the difference in brightness. Image (click to enlarge): The images on the left (unlabeled at top and labeled at bottom) were acquired July 3, 2004. Those on the right were taken June 6, 2005. In the 2005 images, new dark areas are visible and have been circled in the labeled version. The very bright features are clouds in the lower...

Beginnings of a Brown Dwarf Census

by Paul Gilster | Jan 29, 2009 | Deep Sky Astronomy & Telescopes | 6 Comments

Just how common are brown dwarfs? The answer is still up for debate, for stars like these (with masses less than 0.05 that of the Sun) are so small that they do not burn hydrogen, and as they age, they become more and more difficult to detect. But we'd like to know more, especially in understanding our local interstellar neighborhood. Red dwarfs are common throughout the galaxy, and we know that they can support planetary systems and even worlds in the habitable zone. Is it possible that brown dwarfs are even more numerous than red dwarfs? Asking questions like these takes us into what is known as the initial mass function (IMF), which involves the number of stars versus their masses at the time of their formation. The place to study the issue is a star forming region like the one shown in the image below. This Subaru Telescope composite shows the W3 Main region, about 6,000 light years away in the constellation Cassiopeia. A region like this is helpful because the majority of stars...

Most Accurate Exoplanet Image Yet

by Paul Gilster | Jan 28, 2009 | Exoplanetary Science | 11 Comments

I absolutely love the image below, so I decided to run it at full size although it doesn't quite fit the column width. You're looking at the result of recent work from the California & Carnegie Planet Search team, which used data from the Spitzer Space Telescope to produce what is probably the most accurate image yet of an exoplanet. It's not an actual photographic image, of course, but it's better than an artist's interpretation because it's based on highly realistic simulations. The planet in question is HD 80606b, which circles a star about 200 light years from Earth. This is a highly interesting place, some four times the mass of Jupiter and moving within a 111-day orbit around its star. What makes it stand out is the incredible eccentricity of its orbit. We're talking about a world that for most of its orbit is at distances that would be between Venus and Earth here in our system. But then it swoops in ever closer to its primary until it closes to within 0.03 AU, an encounter it...

A Crowded Inner System

by Paul Gilster | Jan 27, 2009 | Asteroid and Comet Deflection | 6 Comments

A small asteroid hitting the Earth's atmosphere is a spectacular phenomenon, but one likely to go unseen if the object has not been previously tracked. But that may be changing as we continue to install automated cameras across the planet. Take a look at this video of the object that exploded over Scandinavia on January 17. A Swedish camera recorded the event, which now goes worldwide over the Net thanks to the camera's owner, one Roger Svensson, and spaceweather.com. The January 17 incident was little more than a lightshow, startling for local wildlife but unnoticed by the sleeping nation beneath the brief glare. It does, however, remind us of the 1017 potentially hazardous asteroids (PHAs) now known to scientists. A PHA is an asteroid larger than 100 meters that may come closer than 0.05 AU to Earth. Prowling around the spaceweather.com site, I find twelve Earth-asteroid encounters this January alone, the closest being the 1.8 lunar distance passage of 2009 BD on January 25. Only...

A Science Fictional Take on Being There

by Paul Gilster | Jan 26, 2009 | Astrobiology and SETI | 19 Comments

If you're not a member of the Science Fiction and Fantasy Writers of America (still commonly known as the SFWA from the days before the 'fantasy' bit was added), you may not see the group's regular bulletin. That would be understandable, given that although it can be found on newsstands, the SFWA Bulletin now costs a solid $6.95 per copy. Nonetheless, keeping up with Robert Metzger's 'State of the Art' science column would keep me buying this journal even if it didn't come as part of my membership. Metzger, the author of the 2002 novel Picoverse and 2005's CUSP as well as a variety of short fiction in addition to his science writing (some of which is available online), speculates in his most recent column on a subject we've recently treated here. Would a species capable of star travel actually need to make the journey, given the advances in technology that would surely make it possible to learn more and more about exoplanets from its own star system? Metzger reviews current exoplanet...

A Workable Fusion Starship?

by Paul Gilster | Jan 23, 2009 | Advanced Rocketry | 44 Comments

by Adam Crowl In the market for a mammoth starship? Recently released work by Friedwardt Winterberg, discussed here by Adam Crowl, points to fast interplanetary travel and implies possibilities in the interstellar realm that are innovative and ingenious. Adam notes in an e-mail that Winterberg's drive has certain similarities to MagOrion, a system that in its earliest iteration combined a magnetic sail with small yield nuclear fission devices. Dana Andrews and Robert Zubrin first published that concept in 1997 and it has been evolving in the years since, but Winterberg's work takes the idea into the realm of what may be a truly workable fusion design. Read on as we follow up our earlier story on Winterberg with a much deeper look. Friedhardt Winterberg has worked on inertial confinement fusion since 1954 and was extensively involved in developing new fusion devices during the Cold War alongside bomb-makers like Edward Teller. Much of his non-fission triggering work was classified,...

Dark Matter and Galactic Origins

by Paul Gilster | Jan 22, 2009 | Deep Sky Astronomy & Telescopes, Exotic Physics | 3 Comments

Understanding how galaxies form is no easy matter, particularly when you factor in dark matter. Without a firm knowledge of what dark matter actually is, we're limited to discussing its perceived effects, something that researchers at Hebrew University of Jerusalem have coupled with computer simulations that change how we view the early universe. The large galaxies some three billion years after the Big Bang apparently didn't form from the merger of smaller disks of material, says this team. That earlier theory would have seen slow star formation as the various disks eventually came together. But the latest observations show that early galaxies created stars at a rapid rate. The new theory may explain why. It sees galaxies forming as the result of cold hydrogen flowing in narrow streams along the filaments of the so-called 'cosmic web' that defines the large scale structure of matter in the universe. These hydrogen streams would feed into the halos of dark matter that are believed to...

Detecting Alien Vegetation

by Paul Gilster | Jan 21, 2009 | Exoplanetary Science | 4 Comments

Could we find evidence of vegetation on distant exoplanets? The answer may be yes, according to recent work by Luc Arnold (Observatoire de Haute Provence) and team. If green vegetation on another planet is anything like what we have on Earth, then it will share a distinctive spectral signature called the Vegetation Red Edge, or VRE. The new paper creates climate simulations that explore whether planets with a distinctively different climate than modern Earth's could be so detected. Two earlier eras are useful here. The Last Glacial Maximum (LGM) occurred 21,000 years ago, with global temperatures on the order of 4 degrees Celsius colder than today, and a significantly lower sea level that produced more land surface. The Holocene, 6,000 years ago, is marked by a rising sea level amidst the de-glaciation occurring in the northern hemisphere. Perhaps the most striking contrast with today would be the Sahara, much more laden with vegetation than at any time since. Both provide a useful...

Earth-mass Exoplanets and Their Uses

by Paul Gilster | Jan 20, 2009 | Culture and Society, Exoplanetary Science, Sail Concepts | 19 Comments

What would it take to energize the public about interstellar flight? The answer seems obvious: Discover an Earth-type planet around another star. As happened with Gliese 581 c, once thought to be potentially habitable, the media would quickly focus on the question of how to get there. Interviewed by the BBC on that topic, I found myself explaining that a star over twenty light years away was an impossible target at our current level of technology, but the discussion quickly opened up into what we could do about that, and what methods might evolve to allow star travel. The point is to get people thinking not only about distances but methods. Right now we're still in the 'build a better rocket' mindset, one that doesn't comprehend the realities of adding more fuel just to push still more additional fuel. The equations are inexorable: Rockets can't do the job when we're talking about crossing light years, so we look for ways to leave the propellant at home. And because even fast solar...

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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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