Our understanding of habitable zones is a work in progress, but the detection of multiple planets with potentially water-bearing surfaces around TRAPPIST-1 is heartening. Today we examine the prospect of extending the habitable zone further out from the host star than previously thought possible. The idea is found in new work by Ramses Ramirez and Lisa Kaltenegger (both at the Carl Sagan Institute at Cornell University). Volcanism is the key, allowing interactive effects that pump up greenhouse warming and sustain habitability. Go back for a moment to the habitable zone limits that Andrew LePage looked at yesterday in his analysis of TRAPPIST-1. The classical habitable zone -- allowing liquid water to exist on the surface -- has an inner edge at which surface temperatures become high enough to lead to a runaway greenhouse and the rapid loss of water. The outer edge is defined by the distance beyond which CO2 can no longer produce the needed greenhouse effect to keep the surface warm....

When the news about the seven planets of TRAPPIST-1 broke, I immediately wondered what Andrew LePage's take on habitability would be. A physicist and writer with numerous online essays and a host of articles in magazines like Scientific American and Sky & Telescope, LePage is also a specialist in the processing and analysis of remote sensing data. He has put this background in data analytics to frequent use in his highly regarded 'habitable planet reality checks,' which can be found on his Drew ex Machina site. Having run a thorough analysis of the TRAPPIST-1 situation the other day, Drew now gives us the gist of his findings, which move at least several of the TRAPPIST-1 planets into a potentially interesting category indeed. By Andrew LePage Like so many other people interested in exoplanets, I made it a point to watch NASA's press conference live on February 22. Based on the list of participants released by NASA a couple of days earlier, a number of people (myself included)...

Let's turn the clock back a bit on the TRAPPIST-1 discoveries with a reminder of Hubble work on this system announced last July. A team led by Julien de Wit (MIT) used the Hubble Space Telescope's Wide Field Camera 3 to look for atmospheres on TRAPPIST-1b and 1c, two of the three planets then known around this star. The researchers were able to take advantage of a rare simultaneous transit, when both planets crossed the star within minutes of each other, an event that has been calculated to occur only every two years. The result: No sign of the kind of hydrogen-dominated atmospheres we would expect on gaseous worlds. That was good news, for reasons that Nikole Lewis (Space Telescope Science Institute) explained: "The lack of a smothering hydrogen-helium envelope increases the chances for habitability on these planets. If they had a significant hydrogen-helium envelope, there is no chance that either one of them could potentially support life because the dense atmosphere would act...

In yesterday's news conference on the seven planets around TRAPPIST-1, exoplanet scientist Sara Seager (MIT) pointed to the discovery as accelerating our search for habitable worlds. "Goldilocks," Seager said in a finely chosen turn of phrase, "has many sisters in this system." I think she's exactly correct, even though we don't yet know if any of these particular worlds house life. For as Seager went on to point out, we now need to study the atmospheres of these planets to find out what's really going on, especially on potentially habitable TRAPPIST-1e, f and g. Seager's enthusiasm for TRAPPIST-1 is based on the fact that, whatever we eventually learn about its planets, we're seeing such an abundance of possibilities here that similar, possibly life-bearing systems are doubtless commonplace. And with this system, we have transiting worlds in the solar neighborhood whose atmospheres can be analyzed by upcoming missions like the James Webb Space Telescope, or via installations on the...

The red dwarf known as TRAPPIST-1 could not have produced a more interesting scenario. Today we learn that the star, some 40 light years out in the constellation Aquarius, hosts seven planets, all of which turn out to be comparable to the Earth in terms of size. Moreover, these worlds were discovered through the transit method, meaning we have mass and radius information for all of them. Today's report in Nature tells us that three of the planets lie in the habitable zone, and thus could have liquid water on their surfaces. TRAPPIST-1 b, c, d, e, f, g and h are the worlds in question, and all but TRAPPIST-1h appear to be rocky in composition, based on density measurements drawn from the mass and radius information. Drawing on existing climate models, the innermost planets b, c and d are probably too hot to allow liquid water to exist, while h may be too distant and cold. But the European Southern Observatory is reporting that TRAPPIST-1e, f and g orbit within the star's habitable...

You'll want to see the news conference scheduled by NASA at 1300 EST (1800 UTC) today, an exoplanet finding of considerable interest to Centauri Dreams readers (I'll have more on this later in the day). The event will air live on NASA Television and the agency's website. Links available here. Briefing participants: * Thomas Zurbuchen, associate administrator of the Science Mission Directorate at NASA Headquarters in Washington * Michael Gillon, astronomer at the University of Liege in Belgium * Sean Carey, manager of NASA's Spitzer Science Center at Caltech/IPAC, Pasadena, California * Nikole Lewis, astronomer at the Space Telescope Science Institute in Baltimore * Sara Seager, professor of planetary science and physics at Massachusetts Institute of Technology, Cambridge A Reddit AMA (Ask Me Anything) about exoplanets will be held following the briefing at 1500 EST (2000 UTC) with scientists available to answer questions in English and Spanish.

I'm always interested in ways readers can dig directly into data from our telescopes, and this morning I can point to two. I'll begin with the Lick Carnegie Exoplanet Survey, which has just released 60,949 precision Doppler velocities for 1,624 stars. The data draw on observations using HIRES (the High Resolution Echelle Spectrometer) on the Keck 1 telescope on Mauna Kea (Hawaii). As exoplanet hunter Greg Laughlin (UC-Santa Cruz) explains on his systemic site, the data contain hundreds of possibly planetary signals. If you'd like to dig into this material, which includes hints of a super-Earth around the fourth closest star to the Sun (Lalande 21185), I'll remind you of Stefano Meschiari's Systemic Console, developed with Laughlin as a way of exploring exoplanetary data. The latest version completely reworks the older Console and provides the tools needed to study the Lick Carnegie material. Versions of this open source software are available here, and a visit to the Earthbound...

It's no surprise that planets can affect the stars they orbit. We've used that fact for several decades now, relying on radial velocity studies that showed the movement of a star toward us and then away again as it was tugged on by the planet under investigation. But now we're hearing about another kind of planetary effect, one whose future uses may be intriguing. We're seeing a star's brightness change in evident synchrony with a planetary orbit. The star is some 370 light years away from the Earth. The planet in question is HAT-P-2b, a 'hot Jupiter' in a highly elliptical orbit that makes its closest approach to the star every 5.6 days. The planet, discovered by the automated HATNet project (Hungarian Automated Telescope Network), is about 8 times Jupiter's mass. The temperature changes its orbit should induce in its atmosphere led indirectly to the brightness discovery, for researchers led by Julien de Wit (MIT) wanted to learn about the circulation of energy in the planet's...

We're beginning to find evidence of objects like those in the Kuiper Belt beyond our own solar system. In this case, the work involves a white dwarf whose atmosphere has been recently polluted by an infalling object, giving us valuable data on the object's composition. The work involves the white dwarf WD 1425+540, whose atmosphere has been found to contain carbon, nitrogen, oxygen and hydrogen. The findings are unusual because white dwarfs are the dense remnants of normal stars, with gravitational fields strong enough to pull elements like these out of their atmospheres and into their interiors, where they are immune from detection by our instruments. And that implies a relatively recent origin for these elements. Lead author Siyi Xu (European Southern Observatory) and team worked with spectroscopic observations from HIRES (the High Resolution Echelle Spectrometer) on the Keck Telescope and included data from the Hubble instrument. The researchers believe the white dwarf's...

When it comes to the nearest stars, our focus of late has been on Proxima Centauri and its intriguing planet. But of course the work on Centauri A and B continues at a good clip. The prospects in this system are enticing -- a G-class star like our own, a K-class dwarf likewise capable of hosting planets, and the red dwarf Proxima a scant 15000 AU away. Project Blue examines how we might image planets here as our radial velocity studies proceed. But we have much to learn, and not just about possible planets. A new paper by Pierre Kervella (Observatoire de Paris), working with Lionel Bigot and Fréderic Thévenin (both at the Observatoire de la Cote d'Azur), reminds us of the importance of firming up our stellar data. We need to learn as much as possible about Centauri A and B not just because we'd like to find planets there but also because the work has implications for space missions, including the ESA's Gaia, which will tighten our distance measurements to many stars....

We've looked at the factors that are problematic for life around red dwarf stars for some time now, focusing on tidal lock (in which one side of the planet always faces the star) and stellar flare activity, which could dramatically affect life on the surface. A new paper from Vladimir Airapetian (NASA GSFC) and colleagues homes in on the latter problem, offering the idea that we should re-shape our notion of the habitable zone to include space weather. A planet in the habitable zone of any kind of star, according to the definition used most commonly today, is one on which liquid water could exist on the surface. But is this painting the habitable zone with too broad a brush? Because if we allow X-ray and extreme ultraviolet emissions into the picture -- these are common on red dwarf stars, and especially on younger ones -- then even clement temperatures at a planetary surface may not be enough. The problem: Stellar eruptions like flares and, in their most extreme form, coronal mass...