So often planets described as ‘potentially habitable’ turn out to be over-rated -- we look deeper into their composition and characteristics only to find that the likelihood of liquid water on the surface is slim. How to make more accurate calls on the matter of habitability? One way may be to combine orbital and atmospheric models, adjusting each with the known parameters of the planet in question. A new study does just that for the interesting world Kepler-62f. About 1200 light years from Earth in the direction of the constellation Lyra, Kepler-62f has a radius 40 percent larger than Earth’s, which puts it well below the 1.6 RE demarcation line that is increasingly thought to define the difference between Earth-like worlds and planets that are more like Neptune. We’re probably looking at a rocky planet here. It’s also a planet that orbits its K-class primary at a distance that could place it in the outer regions of the habitable zone (as defined, again, by the presence of liquid...

I suppose the most famous fictional depiction of the Sun as it swells to red giant stage is in H. G. Wells’ The Time Machine, in a passage where the time traveler takes his device by greater and greater jumps into the remote future. This is heady stuff: I moved on a hundred years, and there was the same red sun–a little larger, a little duller–the same dying sea, the same chill air, and the same crowd of earthy crustacea creeping in and out among the green weed and the red rocks. And in the westward sky, I saw a curved pale line like a vast new moon. ‘So I travelled, stopping ever and again, in great strides of a thousand years or more, drawn on by the mystery of the earth’s fate, watching with a strange fascination the sun grow larger and duller in the westward sky, and the life of the old earth ebb away. At last, more than thirty million years hence, the huge red-hot dome of the sun had come to obscure nearly a tenth part of the darkling heavens. Wells would have had no real idea...

What’s a movie director supposed to do about gravity? In The Martian, we see Matt Damon moving about on Mars with a gait more or less similar to what he would use on Earth, despite Mars’ 0.38g. Harrison Ford changes worlds but never strides in The Force Awakens. About the gravitational challenges of 1953’s Cat Women of the Moon, the less said the better. Even so, we can chalk all these problems up to the fact that both top directors and their B-film counterparts are forced to film at the bottom of a gravity well, so a certain suspension of disbelief is at least understandable. But assuming that gravity invariably increases as planets get bigger can be misleading, as Fernando J. Ballesteros (Universitat de València) and Bartolo Luque (Universidad Politécnica de Madrid) demonstrate in a new paper in Astrobiology. We learn that some larger worlds in our own Solar System have gravity not all that different from the Earth. In fact, the surface gravities for Venus, Uranus, Neptune and...

If you look into the software that made possible yesterday's exoplanet results, you'll find that VESPA (Validation of Exoplanet Signals using a Probabilistic Algorithm) is freely available online. The work of Princeton's Timothy Morton, who spoke at the announcement news conference, VESPA is all about calculating the probabilities of false positives for signals that look like transiting planets. Transits, of course, are what the Kepler space telescope has been about, catching the slight stellar dimming as a planet crosses across the face of a star. The numbers quickly get mind-boggling because while Natalie Batalha (NASA Ames), joined by Morton, NASA's Paul Hertz and Kepler/K2 mission manager Charlie Sobeck (a colleague of Batalha at Ames) could point to 1284 newly confirmed exoplanets, they represent only a fraction of what must be in the Kepler field of view. Out of its over 150,000 stars, Kepler can only see the planets that transit their host stars, making this a problem of...

About forty light years from Earth in the constellation Aquarius is the star designated 2MASS J23062928-0502285, which as of today qualifies as perhaps the most interesting ultracool dwarf we've yet found. What we learn in a new paper in Nature is that the star, also known as TRAPPIST-1 after the European Southern Observatory's TRAPPIST telescope at La Silla, is orbited by three planets that are roughly the size of the Earth. We may have a world of astrobiological interest -- and conceivably several -- orbiting this tiny, faint star. Image: Comparison between the Sun and the ultracool dwarf star TRAPPIST-1. Credit: ESO. If we untangle the TRAPPIST acronym, we find that it refers not to an order of monks (famous for their beers) but to the TRAnsiting Planets and PlanetesImals Small Telescope, a 60 cm robotic instrument that is operated from a control room in Liège, Belgium. TRAPPIST homes in on sixty nearby dwarf stars at infrared wavelengths to search for planets. Michaël...