The budgetary demise of Terrestrial Planet Finder has cast a pall over some researchers, but it may have energized an entirely different solution. What if I told you that in the 2013-2015 time frame we may get conclusive images that tell us whether or not there are terrestrial worlds around Tau Ceti, Epsilon Eridani, and Centauri A and B? Images that allow us to examine the habitable zones of as many as 100 stars over a three-year period? With TPF gone, the idea sounds like a fantasy, but my recent conversation with astronomer Webster Cash revealed it to be anything but. Cash (University of Colorado at Boulder) has been involved in the development of a concept most recently called New Worlds Imager, one that began as an enormous 'pinhole camera' design, as I discussed in Centauri Dreams (the book) in 2004. Within the last 18 months, the design has morphed into a low-cost mission using an occulter (call it a 'starshade') to mask the light of the star being observed so as to reveal...

Margaret Turnbull (Carnegie Institution of Washington) has a job Centauri Dreams can't help but envy. The astronomer is a specialist in identifying stars that have habitable zones -- stars, in other words, where life is possible. Back in 2003, Turnbull and colleagues published a list of 17,129 such stars, based on factors such as age (how long does it take life to develop?), stellar mass (larger stars may not live long enough to produce productive habitable zones) and metallicity (a measure of the heavy metals needed for planetary formation). Narrowing a galaxy of between one and two hundred billion stars down to 17,129 candidates is no small feat, but Turnbull has now gone one better, choosing the top five candidate stars for those engaged in SETI, the search for extraterrestrial intelligence. That list involves choosing stars where technological civilizations are most likely to have developed, but Turnbull complements it with a second list of six stars likely to have Earth-like...

Greg Laughlin's systemic site, indispensable for those studying exoplanet detections, now offers a close look at Proxima Centauri, at 4.22 light years the closest known star to the Sun. Intriguing facts include these: While holding about 11 percent of the Sun's mass, Proxima has an average density several times that of lead (the Sun's average density is about 1.4 times that of water) Proxima's total luminosity is a thousand times less than the Sun's Because radiation alone cannot get Proxima's fusion energy from its interior to the surface, the star relies on convection -- the motion of stellar gases physically takes energy away from the core (by contrast, the Sun has a radiative core) All of which has powerful consequences, especially in terms of longevity -- Proxima Centauri will still be shining two trillion years from now. You'll want to read the entire post, which goes into the details of a paper Laughlin wrote (with Peter Bodenheimer and Fred Adams) that examines the fate of...

A fascinating post by Anthony Kendall cites the reasons why Terrestrial Planet Finder is such an important mission and goes on to call for NASA's being broken into separate entities, to make missions like this more likely to launch. From the Anthonares weblog: Gradually, constructing, launching, and operating missions in Earth orbits or in Lagrange points should be taken over by consortia similar to those that operate ground-based facilities today. As commercial satellite companies have demonstrated, they are more than capable of managing their own facilities. NASA's deep space expertise will necessitate the existence of an unmanned space probe agency for several decades at least, and perhaps indefinitely as we look to explore the stars. The TPF missions could be the first in step in this process. If the scientific community wants them badly enough, they have the lobbying ability (as demonstrated with Hubble and New Horizons) to get Congress to fund them. Since private consortia will...

The key lesson of exoplanetary science is surely humility. Over and over again, starting with the discovery of the first 'hot Jupiters,' we've been brought face to face with the fact that assumptions long enshrined in our thinking have to be reevaluated. Thus it's no surprise to learn of a new study identifying what appear to be enormous debris disks around two giant stars. In the past, stars of their size were considered unlikely candidates for planetary systems. The stars are R 66 and R 126, both located in the Large Magellanic Cloud; the former is 30 times more massive than our Sun, the latter 70 times. Both are thought to be descendants of the massive objects called type O stars, large enough that, if they were located in our own Solar System, they would swallow all the inner planets including Earth. Image: This illustration compares the size of a gargantuan star and its surrounding dusty disk (top) to that of our solar system. Monstrous disks like this one were discovered around...