While we’ve all had our eyes fixed on TRAPPIST-1 (amid the still lingering excitement of the discovery of Proxima Centauri b), news about another stellar neighbor has caused only a faint stir. But what’s happening around HD 219134 (Gliese 892) is noteworthy, and it’s interesting to see that Michaël Gillon (University of Liège – Belgium) has had a hand in it. Gillon, after all, led the work on TRAPPIST-1’s two waves of exoplanet discoveries, culminating in the startling assemblage of seven Earth-sized worlds around the dim ultracool dwarf star. HD 219134 is an orange K-class star (K3V) in the constellation Cassiopeia, and only about half the distance, at 21.25 light years, as TRAPPIST-1 (about 40 light years out). It was known before the recent Gillon et al. paper in Nature Astronomy that we had a super-Earth, HD 219134 b, in orbit here, which was soon joined by two more super-Earths, a gas giant and, a few months later, another two planets, making for a total of six. This system...

K2 Campaign 12 is an observational window that comes at the right time. Operating as the K2 mission, the Kepler spacecraft collected data from December 15, 2016 to March 4 of this year on the TRAPPIST-1 system. With seven planets, at least six of them likely to be rocky worlds, TRAPPIST-1 is suddenly high on everyone's target list for future observation. The new Kepler data are a key part of this, as Geert Barentsen, K2 research scientist at NASA's Ames Research Center at Moffett Field, California, explains: "Scientists and enthusiasts around the world are invested in learning everything they can about these Earth-size worlds. Providing the K2 raw data as quickly as possible was a priority to give investigators an early look so they could best define their follow-up research plans. We're thrilled that this will also allow the public to witness the process of discovery." The raw cadence data -- 'cadence' refers to the time between observations of the same target -- are available from...

The seven planets circling the star TRAPPIST-1 have been lionized in the media, and understandably so, given that more than one have the potential for habitability. But of course M-dwarfs call up the inevitable problems associated with such tiny stars. Habitable planets must orbit close to the star, with the probability of tidal lock and subsequent climatic issues. Moreover, the flare activity particularly in young M-dwarfs gives cause for concern. It's the latter issue that Jack T. O'Malley-James and Lisa Kaltenegger (both at Cornell, where Kaltenegger is director of the Carl Sagan Institute) have explored in a new paper to be published in The Astrophysical Journal. As the paper explains, the question of habitability becomes troubling when we realize how frequently an M-dwarf can flare. Proxima Centauri, an M5 star, undergoes intense flares every 10 to 30 hours, with effects on the planet in its habitable zone that are still unknown. Can a planet with high doses of ultraviolet...

Are we homing in on a 'missing link' in our theories of planet formation? Perhaps so, judging from the work of researchers at Swinburne University of Technology, Lyon University and St. Andrews University. The work does not challenge a central principle in current thinking, that planets form out of disks of gas and dust grains around young stars. We know that these dust grains grow into centimeter-sized aggregates. We also know that, much later, planetesimals (kilometers in size) grow into planetary cores. What has been missing is an understanding of how the early 'pebbles' are able to aggregate into asteroid-sized objects. One problem is that drag in the disk produced by surrounding gas makes the grains move inward toward the star, a movement that can deplete the disk. The paper describes this as a 'radial drift barrier,' in which the grains settle to the midplane of the disk and drift inwards as they lose angular momentum. Taken to its conclusion, the process can lead to accretion...

The binary system SDSS 1557, about 1000 light years from Earth, was thought to be a single white dwarf star until detailed measurements revealed that the brighter star was being gravitationally influenced by a hither unseen brown dwarf. And that, in turn, has given us an intriguing look at possible planetary formation around both members of a close binary. We've found gas giants in such systems, but researchers led by Jay Farihi (University College London) have found signs of rocky debris here that point to the possibility of planets of a much different composition. "Building rocky planets around two suns is a challenge," says Farihi, "because the gravity of both stars can push and pull tremendously, preventing bits of rock and dust from sticking together and growing into full-fledged planets. With the discovery of asteroid debris in the SDSS 1557 system, we see clear signatures of rocky planet assembly via large asteroids that formed, helping us understand how rocky exoplanets are...

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...

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...