While we continue to labor over the question of planets around Alpha Centauri A and B, Proxima Centauri -- that tiny red dwarf with an unusually interesting planet in the habitable zone -- remains a robust source of new work. It’s surely going to be an early target for whatever interstellar probes we eventually send, and is the presumptive first destination of Breakthrough Starshot. Now we have news of a possible second planet here, though well outside the habitable zone. Nonetheless, Proxima Centauri c, if it is there, commands the attention. A new paper offers the results of continuing analysis of the radial velocity dataset that led to the discovery of Proxima b, work that reflects the labors of Mario Damasso and Fabio Del Sordo, who re-analyzed these data using an alternative treatment of stellar noise in 2017. Damasso and Del Sordo now present new evidence, working with, among others, Proxima Centauri b discoverer Guillem Anglada-Escudé, and incorporating astrometric data from...

We rightly celebrate exoplanet discoveries from dedicated space missions like TESS (Transiting Exoplanet Survey Satellite), watching the work go from initial concept to first light in space and early results. But let's not forget the growing usefulness of older data, tapped and analyzed in new ways to reveal hidden gems. Thus recent work out of the Carnegie Institution for Science, where Fabo Feng and Paul Butler have mined the archives of the Ultraviolet and Visual Echelle Spectrograph survey of 33 nearby red dwarf stars, a project operational from 2000 to 2007. The duo have uncovered five newly discovered exoplanets and eight more candidates, all found orbiting nearby red dwarf stars. Two of these are conceivably in the habitable zone, putting nearby stars GJ180 and GJ229A into position as potential targets for next-generation instruments. Both of these stars host super-Earths (7.5 and 7.9 times the mass of Earth), with orbital periods of 106 and 122 days respectively. Like the...

As if I don't have enough trouble figuring out acronyms, I now have to figure out how to pronounce acronyms. The issue comes up because a new NASA instrument now in use at Kitt Peak National Observatory is a spectrograph built at Penn State called NEID. Now NEID stands for NN-EXPLORE Exoplanet Investigations with Doppler spectroscopy. Here we have an acronym within an acronym, for NN-EXPLORE itself stands for the NASA-NSF Exoplanet Observational Research partnership that funds NEID. Here's the trick: The acronym NEID is not pronounced 'NEE-id' or 'NEED' but 'NOO-id.' The reason: Kit Peak is on land owned by the Tohono O'odham nation, and the latter pronunciation honors a verb that means something close to 'to see' in the Tohono O'odham language. As a person fascinated with linguistics, I'm delighted to see this nod to a language whose very survival is threatened by the small number of speakers (count me as one infinitely cheered by the resurrection of Cornish, for example). And as...

Among the discoveries announced at the recent meeting of the American Astronomical Society in Hawaii was TOI 700 d, a planet potentially in the habitable zone of its star. TOI stands for TESS Object of Interest, reminding us that this is the first Earth-size planet the Transiting Exoplanet Survey Satellite has uncovered in its data whose orbit would allow the presence of liquid water on the surface. The Spitzer instrument has confirmed the find, highlighting the fact that Spitzer itself, a doughty space observatory working at infrared wavelengths, is nearing the end of its operations. Thus Joseph Rodriguez (Center for Astrophysics | Harvard & Smithsonian): "Given the impact of this discovery - that it is TESS's first habitable-zone Earth-size planet - we really wanted our understanding of this system to be as concrete as possible. Spitzer saw TOI 700 d transit exactly when we expected it to. It's a great addition to the legacy of a mission that helped confirm two of the TRAPPIST-1...

TOI 1338b is a great catch, a circumbinary world that turned up in TESS data and was announced at the ongoing meeting of the American Astronomical Society in Hawai'i. Ravi Kopparapu (NASA GSFC) describes the discovery process in the essay below. The system lies 1,300 light years out in the constellation Pictor, with the planet transiting the larger star. Dr. Kopparapu's work on exoplanet habitability is well known to Centauri Dreams readers. See, for example, his How Common Are Potential Habitable Worlds in Our Galaxy?, which ran in 2014. He followed this up with a look at an unusual multi-planet system (Ravi Kopparapu: Looking at K2-72). Analyzing habitable zone possibilities around different kinds of stars, as well as modeling and characterizing exoplanet atmospheres, plays a major role in his research interests. Here Dr. Kopparapu tells us about the new world and the significant role of an intern in its discovery, reminding us that the opportunities for young scientists to make a...

The Egyptian monarch Khufu was the second pharaoh of the Fourth Dynasty, which dates him back to the earlier years of the Old Kingdom period around the 26th century BC. I mention this figure, about which all too little is known, because his name is a link between the great monuments of an early culture (Khufu seems to have commissioned the Great Pyramid of Giza) and present-day engineering. Imagine how wondrous the Great Pyramid would have been to the average passerby of the time, and then realize that Khufu's Hellenized name was Cheops, a monicker reflected in the acronym of our recently launched CHEOPS exoplanet observatory. I always enjoy untangling acronyms, some of which are more labored than others. Did you know, for example, that the name of the Japanese IKAROS solar sail is actually an acronym standing for Interplanetary Kite-craft Accelerated by Radiation Of the Sun? Then there's OSIRIS-REx (also satisfyingly Egyptian), which weighs in as Origins, Spectral Interpretation,...

An Australian amateur astronomer named Thiam-Guan Tan has made a name for himself in the realm of exoplanets. Tan participated in the discovery of an exoplanet that may orbit within its star's habitable zone. LHS 1140 b is a super-Earth some 41 light years from Earth that orbits a red dwarf star. Back in September of 2016, with a number of professional observatories looking at the host star, Tan provided key data to help verify the existence of LHS 1140b. "It was fortunate that I was able to catch a transit," said Tan, a retired engineer with a 12-inch telescope who has also discovered several supernovae. He is quoted in a newspaper called The West Australian as saying "That night, the Centre for Astrophysics had lined up five other telescopes across Australia and Hawaii to observe but they were all clouded out." Tan's work with exoplanet transits continues, an illustration of the role that talented amateurs with affordable equipment (Tan's telescope cost $15,000) can play. Image:...

Calling it a ‘chance discovery,’ the University of Warwick’s Boris Gänsicke recently presented the results of his team’s study of some 7,000 white dwarf stars, all of them cataloged by the Sloan Digital Sky Survey. One drew particular interest because chemical elements turned up in spectroscopic studies indicating something unusual. Says Gänsicke, “We knew that there had to be something exceptional going on in this system, and speculated that it may be related to some type of planetary remnant.” And that makes the star WDJ0914+1914 an example of what a stellar system that survived, at least partially, the red giant phase of its host star might look like as a planet orbits the Earth-sized white dwarf. This work, which draws on data from the European Southern Observatory’s X-shooter spectrograph at the Very Large Telescope in Chile, confirms hydrogen, oxygen and sulphur associated with the white dwarf, all found in a disk of gas around the star rather than being present in the white...

The interest in 'Oumuamua and comet 2I/Borisov makes it clear that interstellar neighbors wandering into our system generate loads of media coverage. And why not: Here is a way to study material from another stellar system while remaining within our own. 2I/Borisov, for example, reaches its closest approach to Earth in early December, closing to within roughly 300 million kilometers. Whatever pushed an object like this out of the parent system cannot be known, but we're likely dealing with gravitational disruption related to planets in the birth system. But more about that in a moment. For thanks to Yale University astronomers Pieter van Dokkum, Cheng-Han Hsieh, Shany Danieli, and Gregory Laughlin, we have a fine new image of 2I/Borisov. This was taken on November 24 using the W.M. Keck Observatory's Low-Resolution Imaging Spectrometer in Hawaii. The tail of the comet, according to van Dokkum, is about 160,000 kilometers long. Note the size comparison below to be reminded, as always,...

Our fascination with Alpha Centauri doubtless propels at least some of the recent interest in binary star systems, as we ponder the chances for habitable worlds around the nearest stars. But given that the population of binary or multiple star systems in our galaxy is as high as it is (multiple systems are common, and about 50 percent of stars have binary companions), determining the factors that influence habitability in this environment has much broader significance. A new study out of the Georgia Institute of Technology has been looking at the issue by modeling an Earth twin in various binary scenarios. So how does Alpha Centauri fare? We can find habitable zones in the Centauri A/B system, and into these the researchers introduced a simulated Earth around Centauri B to examine its axis dynamics. They also investigate the dynamical evolution of planets within the habitable zone of either star, generalizing from these results to the larger binary star population. The issue to be...

While the majority of exoplanet-hosting stars discovered so far are single, we do have multiple star systems in various configurations with planetary companions. This is fertile ground for study, and not just because the nearest stellar system, Alpha Centauri, contains a tight binary pair that is being closely investigated for planets. The third star here is, of course, Proxima Centauri, around which we already know of the existence of a planet in the habitable zone. The much broader question is, how likely are multiple star systems to host planets? Tackling this question in a new study is Markus Mugrauer (Friedrich Schiller University, Jena), who has been investigating how the existence of multiple stars in a system affects the formation and development of planets. Mugrauer has been working with the second data release from the European Space Agency’s Gaia mission (made available in April of last year). This release contains data collected by Gaia during the first 22 months of its...

The question of habitability on planets around M-dwarfs is compelling, and has been a preoccupation of mine ever since I began working on Centauri Dreams. After all, these dim red stars make up perhaps 75 percent of the stars in the galaxy (percentages vary, but the preponderance of M-dwarfs is clear). The problems of tidal lock, keeping one side of a planet always facing its star, and the potentially extreme radiation environment around young, flaring M-dwarfs have fueled an active debate about whether life could ever emerge here. At Northwestern University, a team led by Howard Chen, in collaboration with researchers at the University of Colorado Boulder, NASA's Virtual Planet Laboratory and the Massachusetts Institute of Technology, is tackling the problem by combining 3D climate modeling with atmospheric chemistry. The paper on this work, in press at the Astrophysical Journal, examines how general circulation models (GCM) have been able to simulate the large-scale circulation and...

It's good to see the European Space Agency's ARIEL mission getting a bit more attention in the media. The Atmospheric Remote-sensing Infrared Exoplanet Large-survey was selected earlier this year as an ESA science mission, scheduled for launch in 2028. Here the goal is to cull a statistically large sample of exoplanets to examine their evolution in the context of their parent stars. Giovanna Tinetti (University College London) is principal investigator. I would urge seeing ARIEL in the context of a different kind of evolution, that being the gradual growth in our technologies as we continue getting closer to studying the atmospheres of terrestrial-class worlds. For while ARIEL cannot achieve this feat -- its focus is on exoplanets of Jupiter-mass down to super-Earths, all on close orbits, with temperatures greater than 320 Celsius -- it leverages the fact that high temperature atmospheres keep their various interesting molecules in continual circulation, rather than letting them sink...

We often think of Jupiter as a mitigating influence on asteroid or comet strikes in the inner system, its gravity changing the trajectories of potential impactors. That would make gas giants a powerful determinant of the survivability of Earth analogues, at least in terms of habitability. While we continue to investigate the question, it's interesting to consider the damage a gas giant on an elliptical orbit might do to habitable zone planets. Stephen Kane (UC-Riverside), working with Caltech astronomer Sarah Blunt, decided to find out what would happen if, in their modeling, they introduced an elliptical gas giant into the system of an Earth twin. You may remember Kane's work earlier this year combining radial velocity with direct imaging methods to find three gas giants that had been previously unobserved (citation below). The monitoring of ten target stars continues even as this new work is published. We're beginning to find more planets at ever larger distances from their stars...

The formation of planets like Neptune under the core accretion model involves a protoplanetary core that reaches around 10 Earth masses before beginning to pull in surrounding gas, the latter being a runaway process that quickly builds the atmosphere around the object. Core accretion is most efficient at doing this just outside the snow line, but if we want to understand and test the theory, we need to know a lot more about how planets are distributed in this region. And that’s a problem, because recent microlensing surveys have found that planets like Neptune are most abundant much more distant from their host stars. Outward migration can account for such worlds, but we know little about exoplanets that form at the snow line, which is where the condensation of ices can factor into the emergence of a new world. Is this just an artifact of our still evolving microlensing detection techniques? Perhaps, and exceptions to the rule can therefore be helpful. Recent work that began with a...

NASA collaborates with the German Aerospace Center (DLR) on one of our more interesting observatories. SOFIA, the Stratospheric Observatory for Infrared Astronomy, is a Boeing 747 aircraft that flies an infrared telescope with a 2.7 m diameter mirror. Located on the port side of the fuselage near the tail, the telescope houses a number of instruments for infrared astronomy at wavelengths from 1-655 micrometers (μm). One of these is FORCAST (Faint Object Infrared Camera for the SOFIA Telescope), which has now spotted an intriguing phenomenon, one that may be flagging a collision of two exoplanets. The stars in question form a double system called BD +20 307, some 300 light years from Earth. Note the age of this system, about one billion years, an important consideration in what follows. About ten years ago, observations from the Spitzer instrument as well as ground observatories produced evidence of warm debris here, whereas from age alone, we would have expected warm circumstellar...

I continue to be fascinated by small stars. My earliest passion for such involved red dwarfs, which appeared to make habitable planet possibilities that would be of great interest to science fiction authors, assuming such environments could survive tidal lock and stellar flaring. But white dwarfs have a weird seductiveness of their own, because we're learning how to extract from them information about planets that orbited them before being consumed. Thus a new paper out of UCLA, which focuses on an unusual way of determining the geochemistry of rocks from beyond our Solar System. We can do this because white dwarfs, the remnants of normal stars that have gone through their red giant phase and collapsed into objects about the size of the Earth, have strong gravitational pull. That means we would expect heavy elements like carbon, oxygen and nitrogen to vanish into their interiors, utterly out of view to our instruments. We should see little more than hydrogen and helium, making what...

The news of a gas giant of half Jupiter's mass around a small red dwarf, GJ 3512 b, continues to resonate. It goes to what has become a well enshrined controversy among those who follow planet formation models. While core accretion is widely accepted as a way of building planets, gravitational instability has remained an option. We are not talking about replacing one model with another, but rather saying that there may be various roads to planet formation among the gas giants. In any case, GJ 3512 b makes a strong case that we have much to learn. When I think about gravitational instability, I go back to the work of Alan Boss (Carnegie Institution for Science), as he has long investigated the concept. I learned about it from his papers and his subsequent book The Crowded Universe (Basic Books, 2009). Here's how Boss describes it there: Proponents of the top-down mechanism… envision clumps of gas and dust forming directly out of the planet-forming disk as a result of the...

The gas giant GJ 3512 b does not particularly stand out at first glance. About 30 light years from the Sun, it orbits its host star in 204 days, discovered by radial velocity methods by the CARMENES collaboration, which is all about finding planets around small stars. But look more deeply and you discover what makes this find provocative. GJ 3512 b turns out to be a gas giant with about half the mass of Jupiter, and small red dwarfs like this one aren’t supposed to host such worlds. In fact, GJ 3512 b is at least an order of magnitude more massive than what we would expect from current theoretical models, making it an interesting test case for planet formation. Core accretion models assume the gradual agglomeration of material in a circumstellar disk, with small bodies banging into each other and growing over time until their gravity is sufficient to draw in an atmosphere from the surrounding gas. This gas giant defies the model, evidently having formed directly from the disk through...

Ongoing in Geneva is the joint meeting of the European Planetary Science Congress and the Division for Planetary Sciences of the American Astronomical Society. We can abbreviate the whole thing as EPSC-DPS 2019, and you can read more about it here. We'll track several stories here as they develop, but I notice that the European Space Agency's ARIEL mission, which is slated to make the first large-scale survey of exoplanet atmospheres, has been supporting a Data Challenge involving removing noise from exoplanet observations. So let's start there. The slant here is training computers to filter out errors in collecting exoplanet data caused by starspots and by instrumentation, with two winners, James Dawson (Team SpaceMeerkat), and Vadim Borisov (Team major_tom), announced yesterday in Geneva. All told, 112 teams registered for the competition, a heartening number illustrative of the growing interest in computational statistics and machine learning among exoplanet researchers. The top...