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...

A key way to learn more about a given exoplanet is to home in on the properties of its star. So argue Stephen Kane (San Francisco State University) and colleagues in a new paper slated for the Astrophysical Journal. The star in question is Wolf 1061 (V2306 Ophiuchi), an M-class red dwarf some 13.8 light years away in the constellation Ophiuchus. In December of 2015, Australian astronomers announced the discovery of three planets around the star. Drawn out of data from the HARPS spectrograph at La Silla, the planets are all super-Earths, their radial velocity data supplemented with eight years of photometry from the All Sky Automated Survey. All three seem likely to be rocky planets, but firming this up would take transits, which the discovery team at the University of New South Wales estimated might occur, with a likelihood of about 14 percent for the inner world, dropping to 3% for the outer. Kane and team investigate the transit question in light of the fact that that two recent...

One of the great joys of science is taking something that seems beyond reach and figuring out a way to do it. We can use a coronagraph, for example, to screen out much of the light of a star to see planets around it, but coronagraphs can only do so much, as planets too near the star are still hidden from view. Now scientists have used an unusual observation to deduce information about one such hidden planet and its interactions with a circumstellar disk. Announced at the recent meeting of the American Astronomical Society, the work involves 18 years of archival observations with the Hubble Space Telescope, which have yielded an intriguing shadow sweeping across the disk of the TW Hydrae system. We're evidently looking at a young planetary system in formation, as the star -- slightly less massive than the Sun and about 192 light years away in the constellation Hydra -- is only about 8 million years old. Helpfully for our work, the TW Hydrae disk is seen face-on from our perspective....

Moving groups are collections of stars that share a common origin, useful to us because we can study a group of stars that are all close to each other in age. Among these, the Beta Pictoris moving group is turning out to be quite productive for the study of planet formation. These are young stars, aged in the tens of millions of years (Beta Pictoris itself is between 20 and 26 million years old). Within the moving group, we've detected planets around 51 Eridani and Beta Pictoris, while infalling, star-grazing objects have been found around Beta Pictoris. Evidence of comet activity around another of these stars was discussed at the American Astronomical Society meeting in Texas. The star HD 172555, 23 million years old and about 95 light years from Earth, shows the presence of the vaporized remnants of cometary nuclei, marking the third extrasolar system where such activity has been traced. All the stars involved are under 40 million years old, giving us a glimpse of the kind of...

Breakthrough Starshot, the research and engineering effort to lay the groundwork for the launch of nanocraft to Alpha Centauri within a generation, is now investing in an attempt to learn a great deal more about possible planets around these stars. We already know about Proxima b, the highly interesting world orbiting the red dwarf in the system, but we also have a K- and G-class star here, either of which might have planets of its own. Image: The Alpha Centauri system. The combined light of Centauri A (G-class) and Centauri B (K-class) appears here as a single overwhelmingly bright 'star.' Proxima Centauri can be seen circled at bottom right. Credit: European Southern Observatory. To learn more, Breakthrough Initiatives is working with the European Southern Observatory on modifications to the VISIR instrument (VLT Imager and Spectrometer for mid-Infrared) mounted at ESO's Very Large Telescope (VLT). Observing in the infrared has advantages for detecting an exoplanet because the...

What effect does the composition of a star have on the planets that form around it? Enough of one that we need to take it into account as we assess exoplanets in terms of astrobiology. So says a study that was presented at the American Astronomical Society meeting in Texas last week, looking at ninety specific stars identified by Kepler as having evidence of rocky planets. We know about the composition of these stars because they are part of the 200,000 star dataset compiled by APOGEE, the Apache Point Observatory Galactic Evolution Experiment spectrograph mounted on the 2.5m Sloan Foundation telescope in New Mexico. APOGEE allows us to examine the spectra of stellar atmospheres to identify their elements. Modeling the formation of planets around these stars shows us the implications for astrobiology. Johana Teske (Carnegie Observatories) explains: "Our study combines new observations of stars with new models of planetary interiors. We want to better understand the diversity of...

Let’s talk this morning about the relationship of Proxima Centauri to nearby Centauri A and B, because it’s an important issue in our investigations of Proxima b, not to mention the evolution of the entire system. Have a look at the image below, which shows Proxima Centauri’s orbit as determined by Pierre Kervella (CNRS/Universidad de Chile), Frédéric Thévenin (Observatoire de la Côte d'Azur) and Christophe Lovis (Observatoire astronomique de l’Universite? de Gene?ve). The three astronomers have demonstrated that all three stars -- Proxima Centauri as well as Centauri A and B -- form a single, gravitationally bound system. Image: Proxima Centauri’s orbit (shown in yellow) around the Centauri A and B binary. Credit: Kervella, Thévenin and Lovis. A couple of things to point out here, the first being the overall image. You’ll see Alpha Centauri clearly labeled within the yellow ellipse of Proxima’s orbit. Off to the right of the ellipse, you’ll see Beta Centauri. I often see the image...

What kind of planets are most common in the outer reaches of a planetary system? It's a tricky question because most of the data we've gathered on exoplanets has to do with the inner regions. Both transit and radial velocity studies work best with large planets near their stars. But a new gravitational microlensing study looks hard at outer system planets, finding that planets of Neptune's mass are those most likely to be found in these icy regions. It should be no surprise that gravitational microlensing has produced few planets, about 50 so far, compared to the thousands detected through transit studies and radial velocity methods. After all, microlensing relies upon alignments that are far more unusual than even the transit method, in which a planet crosses the face of its star as seen from Earth. In microlensing, astronomers look for rare alignments between a distant star and one much nearer. Given the right alignment, the 'bending' of spacetime caused by the nearer star's mass...

The Australian Institute of Physics Congress ends today in Brisbane, concluding a schedule of talks that can be viewed here. Among the numerous research presentations was the description of a new optical chip for telescopes that should help astronomers tease out the image of a planet through thermal imaging, nulling out the light of the host star. The new photonic chip could be a replacement for bulk optics at the needed mid-infrared wavelengths. Harry-Dean Kenchington Goldsmith, a PhD candidate who built the chip at the Australian National University Physics Center, says that the same technology that allows astronomers to penetrate dust clouds to see planets in formation will also be used to study the atmospheres of potentially life-bearing planets. ANU's Steve Madden describes the chip as an interferometer that "adds equal but opposite light waves from a host sun which cancels out the light from the sun," making it possible to detect the much fainter light of a planet. He likened...

The super-Earth K2-3d orbits a red dwarf star in the constellation Leo, some 150 light years from Earth. The outermost of three planets discovered in the system, K2-3d was found in the K2 phase of the Kepler mission (K2 Second Light), following the issues with the spacecraft's reaction wheels that led to the end of the primary mission. Interestingly, while the planet is large (with a radius 1.5 times that of Earth), its density is high and indicative of a solid surface (we can measure the radius of K2-3d by studying the transit light curve, while radial velocity methods yield the planet's mass, allowing astronomers to calculate its density). Given the right atmospheric parameters, liquid water could exist here, although most models show a tidally locked world receiving too much solar flux (1.4 times that of the Earth) to make habitable conditions likely. With an orbital period of 45 days, K2-3d's transits are interesting because the planet is close enough to be a useful candidate for...

The discovery of a super-Earth of about 5 Earth masses orbiting the star GJ 536 is a helpful addition to our catalog of nearby red dwarf planets. About 33 light years out, GJ 536b orbits its primary at a distance of 0.06661 AU, an 8.7 day orbit that is too close to be in the habitable zone. But its very proximity to the star implies the possibility of a transit, which could pay big dividends in spectroscopic studies of its atmosphere. Follow-ups as soon as next year should tell us whether it does in fact transit. The work comes out of the Geneva Observatory, working with researchers in France and Portugal, and involves data from the HARPS (High Accuracy Radial velocity Planet Searcher) spectrograph on the European Southern Observatory’s 3.6 meter telescope at La Silla (Chile). And it has me thinking about the problems and benefits of red dwarf studies. For one thing, astronomers can use nearby M-dwarfs for exoplanet detection because the low mass of the star offers up a robust radial...