Life and pulsars don't seem to mix. But science fiction hasn't shied away from making the connection, as witness Robert Forward's Dragon's Egg (Ballantine, 1980). In the novel, a species called the cheela live on the surface of a neutron star, coping with a surface gravity 67 billion times stronger than that of Earth. An interesting consequence: The cheela live at an accelerated rate, going from the development of agriculture to high-tech in little more than a month, as perceived by the human crew observing the course of their rapid development. Now we have news that two astronomers are considering habitable planets in orbits around pulsars, a venue that to my knowledge Forward never considered, but perhaps more recent science fiction writers have (let me know if you have any references). Alessandro Patruno (Leiden University), working with Mihkel Kama (Leiden and Cambridge University) see reasons for thinking that life might emerge in such an environment, though the kind of...

One of the reasons to pay attention to spectrograph technologies -- and we recently talked about ESPRESSO, which has just achieved ‘first light’ -- is that we’re reaching the inflection point when it comes to certain key observations. Finding planets around Centauri A and B has been the gold standard for a number of researchers, and as Debra Fischer (Yale University) points out, we’re just now getting to where spectrographic technology is up to the challenge. Chile is where much of the action is. Here we find ESPRESSO installed on the European Southern Observatory’s Very Large Telescope at Paranal. But Fischer’s team has built CHIRON at Cerro Tololo, and the paper likewise relies on data from the Geneva team’s HARPS and the UVES installation at the Very Large Telescope Array in the United States. Working with Yale’s Lily Zhao, Fischer has re-examined older data with an eye toward turning once again to Centauri A and B with a new round of observations beginning the year after next....

Any thought that our Solar System offers a template for other stellar systems has pretty much vanished in the panoply of system architectures now exposed to our observation. But it seemed rational, in the days before we knew of the existence of other systems, to imagine that if they were there, they would be more or less well ordered. Planets presumably orbited in the equatorial plane of their star, all more or less co-planar (and if Pluto didn't quite fit the bill, that was just more evidence of the features that would one day cause it to become a 'dwarf planet'). But looking at the eight planets that remained after Pluto's 'demotion,' we see planets that are co-planar within about 7 degrees of difference. And as Ethan Siegel (Lewis & Clark College) points out, if we take Mercury out of the mix, the deviation from the plane is only about two degrees (Mercury's inclination is 7 degrees). Likewise, planets in our system line up well with the Sun's rotation axis. But some systems...

NASA's news conference announcing the discovery of Kepler-90i and Kepler-80g was a delightful validation of a principle that has long fascinated me. We have such vast storehouses of astronomical data that finding the time for humans to mine them is deeply problematic. The application of machine learning via neural networks, as performed on Kepler data, shows what can be accomplished in digging out faint signals and hitherto undiscovered phenomena. Specifically, we had known that Kepler-90 was a multi-planet system already, the existing tools -- human analysis coupled with automated selection methods -- having determined that there were seven planets there. Kepler-90i emerged as a very weak signal, and one that would not have made the initial cut using existing methods of analysis. When subjected to the machine learning algorithms developed by Google's Christopher Shallue and Andrew Vanderburg (UT-Austin), the light curve of Kepler-90i as well as that of Kepler-80g could be...

Until we can start observing the atmospheres of rocky worlds around red dwarf stars, we're left to extrapolate conditions there as best we can. New work discussed at the fall meeting of the American Geophysical Union on Dec. 13 recounts one such attempt, using the planet Mars as a surrogate for a similar world in habitable zone orbit around an M-dwarf. The work draws on data from the MAVEN (Mars Atmosphere and Volatile Evolution) mission, launched in 2013 and now orbiting the Red Planet. Designed to study the deterioration of its atmosphere over time, MAVEN offers insights into exoplanets that are derived from plugging in different stellar values. Image: To receive the same amount of starlight as Mars receives from our Sun, a planet orbiting an M-type red dwarf would have to be positioned much closer to its star than Mercury is to the Sun. Credit: NASA/GSFC. MAVEN co-investigator David Brain (University of Colorado, Boulder) discussed MAVEN data at the meeting, noting that the planet...

The transiting red dwarf K2-18 is about 111 light years out in the general direction of the constellation Leo, with a mass of 40 percent of Sol’s. A super-Earth, K2-18b, was detected here in 2015 through light curve analysis of data from the reconfigured Kepler K2 mission, and we now have the first measurement of the planet’s mass, drawing on radial velocity data from HARPS. The two planet detection methods in conjunction thus firm up our knowledge of a possible habitable zone planet. But they also reveal, in the analysis of Ryan Cloutier (University of Toronto) and colleagues, a second super-Earth, K2-18c, which turns out to be non-transiting, and therefore non-coplanar with K2-18b. As we saw yesterday, HARPS (High Accuracy Radial Velocity Planet Searcher), is capable of drilling down to about one meter per second in the analysis of the stellar wobbles that radial velocity methods examine. The current data set gives us another interesting world while reminding us of the capabilities...

What great news that ESPRESSO, the Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations, has just achieved 'first light.' The spectrograph is installed on the European Southern Observatory's Very Large Telescope at the Paranal Observatory in northern Chile and its powers are prodigious. For ESPRESSO makes it possible, for the first time, to combine the light of all four telescopes at the VLT. This creates an instrument with the light collecting power of a 16-meter telescope, a major enhancement to the exoplanet hunt. Image: The room where the light beams coming from the four VLT Unit Telescopes are brought together and fed into fibres, which in turn deliver the light to the spectrograph itself in another room. One of the points where the light enters the room appears at the back of this picture. Credit: ESO/P. Horálek. Thus the enthusiasm of lead scientist Francesco Pepe (University of Geneva): ESPRESSO isn't just the evolution of our previous instruments...

Why all the fuss about red dwarf planets? We're seeing so much ongoing work on these worlds because when it comes to terrestrial-class planets -- in size, at least -- those around red dwarfs are going to be our first targets for atmospheric characterization. A 'habitable zone' planet around a red dwarf throws a deep transit signature -- small star, big planet -- so that we can use transit spectroscopy to puzzle out atmospheric components. Getting an actual image would be even better, and modifications to the VISIR instrument at ESO's Very Large Telescope, a project Breakthrough Initiatives is involved in along with the ESO, could eventually yield such. We'll know a great deal more about the possibilities as new missions come online, but for now, researchers are doing their best to apply models to what we know and deduce what surface conditions may be like around stars like TRAPPIST-1 and Proxima Centauri. Some of these results are not auspicious if it's life we're looking for. I'm...

TRAPPIST-1 and its seven interesting planets may be the most compelling stellar system we're investigating, given the range of worlds here and the possibilities for analyzing an entire, nearby planetary system. But as we look toward examining systems like this with new space- and ground-based instruments, we may run into problems with searching for biosignatures. Both the TRAPPIST-1 planets and the promising Proxima Centauri b may be tough to characterize. The problem: When searching for biosignatures, we're looking for signs of metabolism, gases that are continually produced and remain out of balance in a planetary atmosphere. Ozone is one piece of the puzzle, one that signifies oxygen. Finding the latter in the same atmosphere with methane would be a compelling biosignature. But ozone could be hard to detect. Ludmila Carone (Max Planck Institute for Astronomy) and colleagues now find that atmospheric circulation in planets close enough to red dwarfs to be in their habitable zone...

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...

Video presentations from the recent Tennessee Valley Interstellar Workshop are beginning to appear online. It's welcome news for those of us who believe all conferences should be available this way, and a chance for Centauri Dreams readers to home in on particular presentations of interest. I published my Closing Remarks at TVIW right after the meeting and will watch with interest as the complete 2017 videos now become available. There are a number of these I'd like to see again. All of this gets me by round-about way to Project Blue, the ongoing attempt to construct a small space telescope capable of directly imaging an Earth-like planet around Centauri A or B, if one is indeed there. For the other talk I gave at TVIW 2017 (not yet online) had to do with biosignatures, and the question of whether we had the capability of detecting one in the near future with the kind of missions now approved and being prepared for launch. This was delivered as part of a presentation and panel...

An object called A/2017 U1, whether it is an asteroid or a comet, is drawing attention because it seems to be an interstellar wanderer. Discovered on October 19 by the University of Hawaii's Pan-STARRS 1 telescope on Haleakala, the object was quickly submitted to the Minor Planet Center by Rob Weryk (University of Hawaii Institute for Astronomy, IFA). Weryk was subsequently able to identify the object in Pan-STARRS imagery from the previous night. Image: This animation shows the path of A/2017 U1, which is an asteroid -- or perhaps a comet -- as it passed through our inner solar system in September and October 2017. From analysis of its motion, scientists calculate that it probably originated from outside our Solar System. Credit: NASA/JPL-Caltech. Thus a nightly search for near-Earth objects may have uncovered an object whose origins lie much further away. A/2017 U1 is about 400 meters in diameter and on a highly unusual trajectory, one that fits neither an asteroid or comet from...

Just how do you go about building a 'super-Earth'? One possibility may be emerging in the study of young debris disk systems with thin, bright outer rings made up of comet-like bodies. Three examples are under scrutiny in work discussed at the recent American Astronomical Society's Division for Planetary Sciences meeting in Provo, Utah. Here, Carey Lisse (JHU/APL) described his team's results in studying the stars Fomalhaut, HD 32297 and HR 4796A. What the scientists are finding is that dense rings of comets can become a construction zone for planets of super-Earth size. The makeup of the material in these ring systems varies, from two that are rich in ice (Fomalhaut and HD 32297) to one that is depleted in ice but rich in carbon (HR 4796A). Take a look at the image below, showing the ring surrounding HR 4796A, and you'll see how strikingly tight the band of dust around this relatively young stellar system is. Image: Gemini Planet Imager observations reveal a complex pattern of...

Eduardo Bendek's ACEsat, conceived at NASA Ames by Bendek and Ruslan Belikov, seemed to change the paradigm for planet discovery around the nearest stellar system. The beauty of Alpha Centauri is that the two primary stars present large habitable zones as seen from Earth, simply because the system is so close to us. The downside, in terms of G-class Centauri A and K-class Centauri B, is that their binary nature makes filtering out starlight a major challenge. 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. If we attack the problem from the ground, ever bigger instruments seem called for, like the European Southern Observatory's Very Large Telescope in conjunction with the VISIR instrument (VLT Imager and Spectrometer for mid-Infrared) that Breakthrough Initiatives is now working with...

Comparative exoplanetology? That's the striking term that Angelos Tsiaras, lead author of a new paper on exoplanet atmospheres, uses to describe the field today. Kepler's valuable statistical look at a crowded starfield has given us insights into the sheer range of outcomes around other stars, but we're already moving into the next phase, studying planetary atmospheres. And as the Tsiaras paper shows, constructing the first atmospheric surveys. Tsiaras (University College, London) assembled a team of European researchers that examined 30 exoplanets, constructing their spectral profiles and analyzing them to uncover the characteristic signatures of the gases present. The study found atmospheres around 16 'hot Jupiters,' learning that water vapor was present in each of them. Says Tsiaras: "More than 3,000 exoplanets have been discovered but, so far, we've studied their atmospheres largely on an individual, case-by-case basis. Here, we've developed tools to assess the significance of...

When we think about the markers of possible life on other worlds, vegetation comes to mind in an interesting way. We’d like to use transit spectroscopy to see biosignatures, gases that have built up in the atmosphere because of ongoing biological activity. But plants using photosynthesis offer us an additional option. They absorb sunlight from the visible part of the spectrum, but not longer-wavelength infrared light. The latter they simply reflect. What we wind up with is a possible observable for a directly imaged planet, for if you plot the intensity of light against wavelength, you will find a marked drop known as the ‘red edge.’ It shows up when going from longer infrared wavelengths into the visible light region. The red-edge position for Earth’s vegetation is fixed at around 700–760?nm. What we’d like to do is find a way to turn this knowledge into a practical result while looking at exoplanets. Where would we find the red edge on planets circling stars of a different class...