At 10.89 light years from Earth, Ross 128 is the twelfth closest star to the Solar System, a red dwarf (M4V) first cataloged in 1926 by astronomer Frank Elmore Ross. Now we have news that a team working with the European Southern Observatory's HARPS spectrograph (High Accuracy Radial velocity Planet Searcher) at the La Silla Observatory in Chile has discovered an Earth-sized planet orbiting Ross 128 every 9.9 days, a world whose orbit could conceivably place it in the habitable zone, where liquid water could exist on the surface. That gives us a second nearby world in an interesting orbit, the other of course being Proxima Centauri b. What gives the Ross 128 b detection a wrinkle of astrobiological interest is that the star the planet orbits is relatively inactive. Red dwarfs are known for the flares that can flood nearby planets with ultraviolet and X-ray radiation. Compounded with the fact that habitable zone planets must orbit quite close to a parent M-dwarf (given the star's...

Just how elaborate is the planetary system around the nearest star? It’s a question rendered more interesting this morning by the news that the ALMA Observatory in Chile has now detected dust in the system in an area one to four times as far from Proxima Centauri as the Earth is from the Sun. Moreover, there are signs of what may be an outer dust belt, an indication that while we have already discovered Proxima Centauri b, we are looking at a system in which cold particles and debris that could have formed other planets continue to accompany the star. Image: This artist’s impression shows how the newly discovered belts of dust around the closest star to the Solar System, Proxima Centauri, may look. ALMA observations revealed the glow coming from cold dust in a region between one to four times as far from Proxima Centauri as the Earth is from the Sun. The data also hint at the presence of an even cooler outer dust belt and indicate the presence of an elaborate planetary system. These...

The other day I looked at how we can use transit spectroscopy to study the atmospheres of exoplanets. Consider this a matter of eclipses, the first occurring when the planet moves in front of its star as seen from Earth. We can measure the size of the planet and also see light from the star as it moves through the planetary atmosphere, giving us information about its composition. The secondary eclipse, when the planet disappears behind the star, is also quite useful. Here, we can study the atmosphere in terms of its thermal variations. In my recent post, I used a diagram from Sara Seager to show primary and secondary eclipse in relation to a host star. The image below, by Josh Winn, is useful because it drills down into the specifics. Image: A comparison between transits and secondary eclipses (also sometimes called occultations). In a planetary transit, the planet crosses in front of the star (see lower dip) blocking a fraction of the star's brightness. In a secondary eclipse, the...

The Next Generation Transit Survey has come up with an interesting catch. A gas giant close to the size of Jupiter (about 20 percent less massive) has turned up orbiting a red dwarf some 600 light years away, with an orbital period of 2.6 days. With a temperature calculated at 800 Kelvin, NGTS-1b stands out not because it is a 'hot Jupiter' but because stars as small as this one are not normally associated with gas giants. The new planet is, in fact, the largest planet -- compared to the size of its companion star -- ever discovered. Image: Artist's impression of planet NGTS-1b with its neighbouring star. Credit: University of Warwick/Mark Garlick. The Next Generation Planet Survey is a wide-field photometric survey designed to find transiting exoplanets of Neptune-class and smaller around bright stars, using an array of fully-robotic small telescopes operating in the 600-900nm band. The survey is thus sensitive to K and early-M class stars, the goal being to provide targets for...

How likely are we to find a definitive biosignature once we begin analyzing the atmospheres of nearby rocky exoplanets? We have some ideal candidates, after all, with stars like TRAPPIST-1 yielding not one but three potentially life-bearing worlds. The first thing we'll have to find out is whether any of these planets actually have atmospheres, and what their composition may be. 'Habitable zone' is a fluid concept, and that's not just a reference to liquid water on the surface. A relatively dry terrestrial planet, one with little surface water and not a lot of water vapor in the atmosphere, might avoid a runaway greenhouse and manage to stay habitable in an orbit closer to a G-class star than Earth. A planet with an atmosphere dominated by hydrogen could maintain warm temperatures even at 10 AU and beyond. So we'll need to find out what any exoplanet atmosphere is made of, and weigh that against its orbital position near its star. Image: An extended habitable zone that captures some...