Where will we be in the exoplanet hunt by the year 2020? A few of my own guesses would take this form: We should, within even the next year or two, have detected a terrestrial world in a truly unambiguous position within the habitable zone of a star. That star will doubtless be a red dwarf, like Gliese 581, but we can hope for a result that doesn't lend itself to so many conflicting interpretations. The detection method will surely be planetary transit, but even by 2020 we may not know if life exists there. It's also easy to surmise that by 2020 we'll have a terrestrial-class world located within a stellar system not completely dissimilar to our own; i.e., one involving a star much like the Sun, orbited by a rocky world in the habitable zone. We can hope that by 2020 the tools will have been put in place to do spectroscopic observations of the planetary atmospheres involved in small rocky worlds, though so much depends on budgets and the needed tuning up of exquisitely sensitive...

I've always enjoyed Lynette Cook's work. As you can see in the image below, this space artist captures the drama of celestial events by drawing on recent findings. Like Chesley Bonestell, Cook can take you to an exotic place and leave you staring, but her focus is tighter, homing in on exoplanets as filtered through ongoing work at observatories worldwide. The wonders she'll have to work with as we find more and more such worlds can only be imagined. The dazzling collision below is her take on what may be happening as rocky planets form around HD 23514. The star's designation doesn't jump out but its location does, the oft-studied Pleiades star cluster. Joseph Rhee (UCLA) and collaborators have been working infrared wavelengths using the Gemini North Telescope (Mauna Kea) and space-based infrared instruments, measuring the hot dust around this 100-million year old star. HD 23514 is Sun-like enough to add to the intrigue of this exercise, and it's orbited by hundreds of thousands of...

If you're looking for an analog to the Sun, you have to do more than find a solitary G-class star. Three stars markedly like the Sun -- 18 Scorpius, HD 98618, and HIP 100963 -- still differ in having several times more lithium than our star. Figuring out whether the low amount of lithium is an unusual trait has ramifications for the search for life in the cosmos. You could theoretically push the issue by saying that the Sun's composition is unlikely to be found elsewhere, making extraterrestrial life rare. But that conjecture, which was a stretch to begin with, may be dampened by the recent findings about HIP 56948. 200 light years away in the constellation Draco, the star mimics the Sun's lithium levels. And there's an additional bonus: Bill Cochran's team, also at McDonald, has demonstrated that HIP 56948 hosts no 'hot Jupiters,' giant worlds so close to their primary that they orbit in a matter of days. Thus this finding, developed using data from the 2.7-meter instrument at...

I want to get back to James Bickford's antimatter study tomorrow, at which time I'll set up the full report for download here. This work has already elicited plenty of response, both in comments and backchannel, so tomorrow we'll talk about the mechanisms that create antimatter in our Solar System naturally (as opposed to what we do with particle accelerators), and also ponder how realistic missions to harvest such antimatter could be built around technologies currently in the pipeline. Right now, though, the news conference on 55 Cancri is ongoing, the news from this system more and more interesting now that another planet, the fifth, has been discovered. This is the first system found with this many planets, although the assumption is there will be many, many others. But 55 Cancri, some 41 light years away in the constellation Cancer, bears some resemblances to our own Solar System. The farthest planet from the star is a gas giant about four times Jupiter's mass orbiting every 14...

Gliese 581 continues to occupy the attention, and understandably so. At least three planets orbit this M-dwarf, one of which sprang into the public consciousness with the announcement that it might be in its star's habitable zone. But both Gl 581c and d are interesting from the habitability standpoint, even if subsequent discussions have pointed out just how problematic it is to make such judgments on insufficient data. Ponder how tricky the call can be. For being in a circumstellar habitable zone only means that a terrestrial-size planet can have liquid water on its surface. A new paper by Franck Selsis (Centre de Recherche Astrophysique de Lyon), James Kasting (Pennsylvania State) and colleagues wades right into this morass, pointing out how many other factors could make such a planet remain uninhabitable: Water may not be available A high impact rate may prevent the emergence of life The thus far unknown minimum ingredients for life's formation may not be present Gravity may be...

One of the surprises of the early planet-hunting era has been the discovery of 'hot Jupiters,' giant planets orbiting extremely close to their parent star. That these planets should be prolific in our catalog at present makes sense given the nature (and limitations) of radial velocity detection methods, but before we started finding them, there seemed little reason to believe gas giants would exist at orbits within 0.1 AU. Now we see them as evidence that protoplanets can migrate during the formation period, probably causing havoc as they pass through the inner system. Are hot Jupiters the bane of terrestrial planets? You would think so, given the above scenario, with a gas giant clearing planet-forming materials out of the inner disk during its passage. But Martyn Fogg and Richard Nelson (University of London) think otherwise. Their new paper looks at models of terrestrial planet formation and finds that inner disks survive the passage of the inbound giant, resuming their planetary...

Looking through the list of candidate missions selected by the European Space Agency recently, my attention was immediately drawn to PLATO, a planet-finder spacecraft designed to study transiting exoplanets and to measure the seismic oscillations of the stars they orbit. Although at first reminiscent of COROT, PLATO (Planetary Transits and Oscillations of Stars) is really more like an enhanced version of NASA's upcoming Kepler mission, as I'm reminded by Centauri Dreams regular Vincenzo Liguori, who passed along helpful background information. One immediate difference turns out to be field-of-view, which in PLATO is wide indeed due to the observation strategy involved. Unlike COROT or Kepler, PLATO would put photometric techniques to work in the study of relatively bright stars -- 100,000 of these, with another 400,000 studied down to 14th magnitude. The earlier mission concepts are aimed at surveying fainter and more distant stars in a smaller field. Note the significance of this:...

Alpha Centauri A and B have a mean separation of 23 AU. In Solar System terms, that gives you a spacing a bit further from the Sun than the orbit of Uranus. But with the two stars moving around a common center of mass, the distance between them varies over time. Centauri B is sometimes as far from Centauri A as Pluto is from Sol, while at other times it closes as close as Saturn. From a planet around Centauri B, Centauri A would sometimes shine with the light of 5000 full moons, creating day and night sky scenarios that would be, to say the least, striking. Recent research is making it clear that planets can form in such systems, but binaries are tricky, and we still have much to learn about how such planets would form and where, and under what conditions certain kinds of objects are more likely to occur. Twenty percent of the exoplanet systems thus far found are binary, with the majority of these being wide binaries (separated by 250 to 6500 AU, a far cry from our Centauri stars)....

The news from Transitsearch couldn't be better. Long a champion of amateur involvement in the exoplanet hunt, I was delighted to see, via Greg Laughlin's systemic site, that this globally dispersed team of amateur astronomers is behind the confirmed transit observation of the planet HD 17156 b. Amateurs in Italy, the Canary Islands and California made key observations in early September, with confirmatory data coming in from Massachusetts and California on the night of September 30/October 1 as observers heeded Laughlin's online call to participate. Greg has the details and more about the individual observers at his site. The Transitsearch mode is to look at known planet-bearing stars during those times transits might conceivably occur. And it makes stunningly good sense because of two facts: 1) The tools available to dedicated amateurs today are fully capable of this kind of high-quality work; and 2) Telescope time at the major observatories around the world is obviously limited....

Are we seeing an Earth -- or at least a Mars-sized world -- in the making? Look no further than HD 113766, a binary system perhaps ten million years old some 424 light years away, for the story. One of its stars contains a warm dust belt that may be undergoing planetary formation. If that's the case, the emerging planet will orbit in the classical habitable zone, defined as that region where liquid water can exist on the surface. What counts here is the composition of the dusty materials making up its interesting disk. The Spitzer Space Telescope performs its usual yeoman service at this task, its infrared spectrometer flagging the material as a step up from the pristine building blocks of comets. The latter contain interesting organic materials like polycyclic aromatic hydrocarbons (PAHs), along with their water ice and carbonates. But HD 113766's disk contains no water ice, carbonates or fragile organic materials. Image: This artist's conception shows a binary-, or two-star,...

How large a planet is depends upon its composition and mass. Earth is largely made of silicates, with a diameter of 7,926 miles at the equator. Imagine an Earth mass planet made of iron and you're looking at a diameter of a scant 3000 miles. Interestingly, the relationship between mass and diameter follows a similar pattern no matter what material makes up the planet. Running the numbers, an Earth mass planet made of pure water will be 9500 miles across. Sara Seager (Massachusetts Institute of Technology) has been studying these things as part of a project to model the kind of Earth-size planets we're likely to find around nearby stars. About the mass/diameter pattern, she says this: "All materials compress in a similar way because of the structure of solids. If you squeeze a rock, nothing much happens until you reach some critical pressure, then it crushes. Planets behave the same way, but they react at different pressures depending on the composition. This is a big step forward in...

Our assumptions about terrestrial planets seem pretty straightforward. We're only now reaching the level where detecting such worlds becomes a possibility, with advances in ground- and space-based telescopes imminent that will begin to give us an idea how common such planets are. Hoping for the best, we assume Earth-sized worlds in relatively comfortable places are common and even extend our search from G and K-type stars to the much dimmer (and more numerous) M-dwarfs. But what do we mean by a terrestrial planet? Size is an obvious criterion, but so is placement in the kind of habitable zone we would find conducive to our kind of life. That means liquid water at the surface. So far so good, but keep a sharp eye on the wild card in all this: Orbital ecccentricity. It's a measure of how far the orbit of a planet deviates from a circle, and we need to know more about it. Obviously a highly eccentric orbit could swing a planet through the habitable zone and right back out again, never...

Neon isn't an unusual find in spectroscopic studies of massive stars or, for that matter, in observations of novae or the galactic core. Energetic X-ray or ultraviolet emissions can ionize the gas, at which point it produces infrared light at characteristic wavelengths. Not expecting to find it around low-mass stars like our Sun, researchers have been surprised to find four Sun-like stars showing neon in their disks as measured by a Spitzer Space Telescope project run by the University of Arizona. That project, called Formation and Evolution of Planetary Systems (FEPS) is run out of Steward Observatory. The idea is to study planet-forming gas around 35 young, solar-type stars. Before this work, none of these stars would have been thought energetic enough to radiate the amount of X-ray and ultraviolet light needed to ionize neon. Unexpected though they might be, the observations are useful because neon, while hardly abundant, offers a precise spectral signature that makes it easier...

I, for one, wouldn't want to be around to witness what happens when the Earth is faced with an ever expanding Sun that has exhausted its hydrogen fuel. Conventional wisdom has it that the planet will likely be engulfed by what will then become a red giant. Certainly Mercury and Venus will, and the Earth's orbit is close enough that it may meet the same fate. But it's intriguing to learn that other outcomes are possible. Thus news out of Iowa State that the planet known as V 391 Pegasi b has evidently survived just such an encounter with its own star. Larger than Jupiter, the distant world in the constellation Pegasus was once situated at roughly the same distance from its parent that the Earth is from the Sun. That distance has changed over time as the star lost its outer regions in the helium flash, the onset of helium fusion that is produced as hydrogen is exhausted and contraction heats the stellar core. Image: An artist's conception of V 391 Pegasi b as it survives the red giant...

Figuring out planetary habitable zones gets a little less theoretical when we start talking about known systems. And when that system is Gliese 581, the interest level rises considerably. After the initial announcements of a possibly habitable planet around that star, Gliese 581c was later analyzed (in a paper by Werner von Bloh and team) as being too close to its star for liquid water to exist. But another planet, the more distant GL 581d, seemed to hold distinct promise of being in the habitable zone. Now a new paper tackles the question with intriguing results. Petr Chylek and Mario Pérez (Los Alamos National Laboratory) find some reason to think that both inner planets in this system may, under special but feasible conditions, have become suitable for life. The thinking here depends upon analyzing planetary environments as they evolve, with reference to our own Solar System in terms of that evolution. Start with this: Early on, Venus, Earth and Mars lost their original,...

We've found our share of unusual planets in the short time since actual observations could be made. A decade ago, it would have been hard to come up with anything more unexpected that a 'hot Jupiter,' orbiting so close to its parent star that its orbital period is measured in scant days. Add in 'super Earths' around dim red dwarfs and pulsar planets (actually the first type of exoplanets to be discovered) like those around the pulsar PSR 1257+12, and you have a bestiary of odd objects in the making. And now an outburst of gamma and X rays from the direction of the galactic center, one first detected with the Swift satellite's Burst Alert Telescope, gives promise of yet another kind of object. Pulsing in X rays 182.07 times per second, the source is clearly a 'millisecond' pulsar, a neutron star spinning at fantastic rates. Precise studies of the X-ray timing data have revealed the existence of a low-mass companion with a minimum mass of seven Jupiters, but there is wide play in that...

It's long been my belief that getting more private money into space research is essential, given the uncertainties of government funding and the need to inject outside ideas and enthusiasm into the game. We're already seeing what will, I think, become explosive growth in commercial rocket ventures aimed at finding cheaper and better ways to reach low-Earth orbit. On the interstellar front, the Tau Zero Foundation is being built to parlay philanthropic donations into a solid base for funding cutting edge research into advanced propulsion technologies. The hunt for exoplanets also partakes of this largesse, as witness a $600,000 gift from the Gloria and Kenneth Levy Foundation that will fund a new spectrometer designed for the Automated Planet Finder being built at Lick Observatory. The instrument will check twenty-five stars every night, studying 2000 stars within 50 light years over the next decade. Doppler shifts in the wavelengths of starlight provide the telltale signs of an...

The Rossiter-McLaughlin effect is an evolving tool for exoplanet research, one that has already begun to pay off. We recently looked at a paper studying whether this quirk of radial velocity methods could help in the detection of a terrestrial-class planet. The effect causes a distortion in radial velocity data during a planetary transit, one that seems to indicate a change in the velocity of the star under study. But in reality there is no change -- what observers see is the effect of the transiting planet on the starlight, as shown in the diagram below. It turns out the effect might be useful in finding planets larger than two Earth radii, but perhaps less so with smaller worlds. However, new work by a Japanese/American team using the Subaru Telescope points to a different observational capability. Observing the extrasolar system TrES-1, the team has been able to measure the angle between the parent star's spin axis and the planet's orbital axis, only the third time such an...

The Hungarian Automated Telescope Network (HATNet) is run out of the Harvard-Smithsonian Center for Astrophysics, with primary stations at Mauna Kea (HI) and on Mt. Hopkins (Arizona). Looking at large fields of stars over many consecutive nights, the automated telescopes involved help astronomers identify the periodic dimming that marks a transiting exoplanet. And with other projects like the Trans-Atlantic Exoplanet Survey (TrES), the XO Project in Maui and the Optical Gravitational Lensing Experiment (OGLE) in Chile operational, transit data are piling up. All of which is useful indeed, for at present we are just nearing 20 transiting planets detected from ground-based observatories. The discovery paper for the most recent HATnet detection makes an interesting point about the size of our sample, declaring it "...still small enough that individual discoveries often advance our understanding of these objects significantly by pushing the limits of parameter space, either in planet...

With the European Space Agency's DARWIN at least a decade off and funding for the Terrestrial Planet Finder as problematic as ever, what would be a suitable interim mission to extend our exoplanet exploration program? COROT is already flying, with the possibility of detecting large terrestrial planets in close orbits, while Kepler should be able to detect Earth-mass planets in Earth-like orbits by 2013 or earlier. All of which is promising, but we're still missing key elements of the puzzle. Take those transiting exoplanets COROT and Kepler track. We'll retrieve a wealth of data, but we probably won't be able to get the kind of spectroscopic information we'd like to see from a more advanced mission. Similarly, ground-based telescopes using adaptive optics, and future space missions like the James Webb Space Telescope should show us hot gas giants, but we'll be unlikely to see planets like our own Jupiter and Saturn, cooler worlds in more distant orbits. The solution? A team of NASA...