The red dwarf Gliese 581 continues to draw the eye, whether or not the putative world Gl 581 g is there or not. The latter, whose existence has been the subject of controversy, would occupy a tantalizing place in its star’s habitable zone, though in some models the planet Gl 581 d might also skirt the outer edge of the HZ. Now we have interesting new work from the European Space Agency’s Herschel space observatory announcing that Gl 581, along with the G-class star 61 Vir, another nearby planetary system, shows the the signature of cold dust at -200 degrees Celsius. It’s an abundant signature, too, meaning that both these systems must have ten times the number of comets found in our own Solar System’s Kuiper Belt. The two papers on this work grow out of a program called, fittingly, DEBRIS (Disc Emission via a Bias-free Reconnaissance in the Infrared/Sub-mm). What the researchers working these data are suggesting is that the lack of a large gas giant in the two systems may relate to...

Red dwarfs offer fascinating astrobiological speculation, allowing us to ponder whether flare activity or tidal lock could be the game-changer that prevents life from developing around them. We have much to learn on that score, but new work from Rory Barnes (University of Washington) and René Heller (Leibniz Institute for Astrophysics, Potsdam) looks beyond red dwarfs to brown and white dwarfs and their own prospects for life. The prognosis: Poor. Planets around these objects, the researchers say, would have an early history that could remove surface water. The problem is nuclear burning and the lack thereof. Yes, both brown and white dwarfs could support a habitable zone, but what sets them apart from red dwarfs is that they cool slowly and continuously, meaning their habitable zones shrink inward toward the star. Imagine, Barnes and Heller say, a planet that starts out as a Venus-like world beset with a runaway greenhouse effect. Eventually the habitable zone contracts enough to...

The discovery of Centauri B b, a small planet with a mass similar to Earth, continues to percolate in the news even if the initial buzz of discovery has worn off. Science News gives the new world a look in a recent article, noting the fact that with an orbital period of 3.236 days, this is not a place even remotely likely for life. Surface temperatures in the range of 1200 degrees Celsius are formidable obstacles, but of course the good news is the potential for other planets around Centauri B and, indeed, around its larger companion. Centauri A may well host interesting worlds, but it's a tough study because it's given to the kind of stellar activity that can more readily mask a planetary signature than the quieter Centauri B. Even so, we can imagine the possibility of two planetary systems in close proximity, a scenario that would surely propel any technological civilization around one to investigate the other. We don't have the driver for spaceflight in our system that an...

At 42 light years from Earth, the star HD 40307 is reasonably within the Sun’s neighborhood, so the news of a potentially habitable planet there catches the eye. HD 40307 is a K-class dwarf, one previously known to be orbited by three super-Earths -- with masses between the Earth and Neptune -- that are too close to the star to support liquid water on the surface. Now we have the discovery, announced in a new paper in Astronomy & Astrophysics, of three more super-Earth candidates found by digging into data from HARPS (the High Accuracy Radial Velocity Planet Searcher) and HIRES (the High Resolution Echelle Spectrograph). Mikko Tuomi (University of Hertfordshire) and team put a new software tool called HARPS-TERRA to work on the archival data that allowed them greater precision in filtering out false positives from stellar activity. Says Tuomi: "We pioneered new data analysis techniques including the use of the wavelength as a filter to reduce the influence of activity on the signal...