Combining the assets of multiple telescopes in the technique known as interferometry has a long pedigree. Using a cluster of small telescopes rather than a single gigantic one is a way to achieve high resolution at sharply lower costs. Take a look at this list of astronomical interferometers working from the visible to the infrared and you'll see how widely spread the technique has become as we've moved from earlier long wavelength observations (including the Very Large Array and MERLIN) toward optical installations and submillimeter interferometers and, now under construction, the Atacama Large Millimeter Array. Observing Earth-like planets from space has often been studied in terms of a space-based array, with separated spacecraft operating in tandem, as in the infrared interferometer concept shown in this image (Credit: JPL). Both the now stalled Terrestrial Planet Finder and the canceled Darwin mission from ESA were looking at interferometry concepts that would have used a...

HD 209458b is perhaps the most persistently studied exoplanet we have, a transiting 'hot Jupiter' that has already revealed a slew of its secrets, including the detection of carbon dioxide, water vapor and methane. I confess that it sometimes seems like black magic to me that we are able to ferret out the signature of organic compounds on worlds we cannot even see. But the transit method is fruitful, and when scientists examine the light of the star during a planetary transit, the tiny portion of that light filtering through the planet's atmosphere can be analyzed. In the case of HD 209458b, we're talking about a three hour transit, one that occurs every 3.5 days as this 'hot Jupiter' makes its rounds. Now we learn that the carbon dioxide detected here can also be studied in terms of its velocity. The result: We have indications of a vast storm, a wind flow that's moving at speeds that defy the imagination. Ignas Snellen (Leiden Observatory, The Netherlands) led the team that...

The release of the first 43 days of Kepler data has demonstrated just how powerful a planet-hunting technology we've put into space. Listen to principal investigator William Borucki (NASA Ames) in a video released yesterday by NASA television: "We're releasing data on 156,000 stars that we've been monitoring with the Kepler mission for 43 days, the first dataset. In these data are some 750 planetary candidates. Some of those are actual planets, some are false positives. Our science team is looking at 400 of those candidates with ground-based telescopes, to figure out which are planets, which aren't." Borucki assumes about fifty percent of the candidates will be false positives, eclipsing binary stars, starspots, or other misleading signals. Now it's in the hands of ground-based telescopes in the Canary Islands, Texas, Arizona and Hawaii to comb through these findings to make the call. The team is also releasing the data for the remaining 350 candidates to the world community of...

One of the problems with determining how planets form is the nature of the dusty gas-rich disks that surround their stars. We're learning as we study these things that the disks around young stars disperse quickly in astronomical terms, within several million years. Thus finding a massive planet around a young star like Beta Pictoris is noteworthy. It demonstrates that such planets can form in short-order. What's doubly fascinating about the new find is that this planet was discovered by direct imaging techniques, and that it is as close to its star as Saturn is to ours. Have a look at the imagery below, made using the European Southern Observatory's Very Large Telescope and an adaptive optics instrument that removes atmospheric blurring and other effects. It's a composite showing the faint source in the 2003 image and contrasting it with the motion of the object as seen in the autumn of 2009. The object can be seen to have moved to the other side of the disk. As we only have direct...

It's AAS week in Miami, and the American Astronomical Society usually gives us plenty to talk about. Inclined orbits, for one thing. In our Solar System, the process of planetary formation seems relatively intuitive. The eight major planets orbit largely in the same plane, reinforcing the idea that the cloud of gas that collapsed to form the Sun contained leftover material that formed into a planet-yielding disk. We can point to outer system objects like Pluto (and certainly Sedna) as exceptions, but they're much further out and subject to gravitational influences that this model can account for. But as Barbara McArthur (University of Texas at Austin) and team told an AAS session yesterday, the star Upsilon Andromedae A has yielded a different result. We already knew that three Jupiter-class planets orbited the star, some 44 light years away and a bit younger and more massive than our Sun. But McArthur's team now has determined the mass of two of the three known planets, and has...

Recent work from the Lick-Carnegie team has found that the M-dwarf HIP 57050 is orbited by a Saturn-mass world with an orbital period of 41.4 days. What catches the eye about this exoplanet is its temperature, some 230 kelvin or -43 degrees Celsius, warm enough to place it in the habitable zone of the star. Based on our knowledge of the gas giants in our own Solar System, it's a natural supposition that this is a world with moons, and if so, their location in the habitable zone draws inevitable comparisons with fictional worlds like Pandora. M-dwarf Habitable Zones So what do we know about M-dwarfs that can help us with this system? For one thing, they're exciting objects for radial velocity studies because of their low mass, making the signature of an orbiting planet more readily apparent than with larger stars. We also know that their low temperatures move their habitable zones in much closer to the star than in our system, ranging from 0.1 to 0.2 AU, corresponding to an orbital...

Yesterday's musings on extraterrestrial contact were inspired both by Stephen Hawking and the surrealist painter Giorgio de Chirico (1888-1978). Whereas Hawking opined that an encounter with an alien culture could be dangerous, my own hunch was that it would be deeply mysterious and perhaps not even understood as contact, given the huge differences in technology between us. That called De Chirico's strange cityscapes to mind, what Walter Wells calls 'their deep and often irrational shadows, their empty walkways and portentous silences.' It helped, of course, that years ago I had reviewed V.S. Naipaul's The Enigma of Arrival, which draws heavily on the De Chirico painting of the same name (shown above). Naipaul's book is a strange, autobiographical meditation whose subject is consciousness confronted with mystery. He imagines one of the two figures in the painting as a traveler and conceives a story based on the scene, one set in what he calls a 'dangerous classical city,' but he soon...

Not long ago I sent out a 'tweet' on the Centauri Dreams Twitter feed talking about the number of planet detection candidates the Kepler mission was working with. Almost immediately I discovered that the story had become unavailable at the Nature News site, making me wonder whether the figures were right, but the story is back up (available here) and I can cite it once again. Thus: Since its launch on 6 March 2009, Kepler, with its 0.95-metre telescope, has been staring at the same field of stars near the northern star of Vega, looking for tiny reductions in starlight caused by a planet passing in front of a star's face. In January, the Kepler team announced the discovery of five new exoplanets. [Kepler principal investigator William] Borucki says that the team, as of last week, has found 328 more candidates — but that as many as 50% of these may be false positives, where objects such binary stars confuse the picture. 328 candidates, and much work ahead in weeding out the...

Meetings like the Royal Astronomical Society's gathering in Glasgow can be overwhelming, with all kinds of news to track via emails, news releases and Twitter. Yesterday we looked at the possible signature of rocky planets in the atmospheres of white dwarfs. But the unusual orbits of planets newly discovered by the WASP project (and follow-up studies of older hot Jupiters) get pride of place as perhaps the most notable announcement so far. WASP (Wide Angle Search for Planets) turned up nine new planets, bumping the exoplanet total to 454), but follow-up studies of these worlds, along with other 'hot Jupiters' from earlier surveys, showed that six out of the 27 examined orbited opposite to the rotation of their host star. Moreover, more than half of the planets studied are misaligned with their star's rotation axis. Image: Exoplanets, discovered by WASP together with ESO telescopes, that unexpectedly have been found to have retrograde orbits are shown here. In all cases the star is...

Kepler, CoRoT and future space missions should give us an estimate of how common small, rocky planets are in the galaxy. But there is much we can do from Earth, as Jay Farihi told the Royal Astronomical Society's 2010 meeting today. Farihi's team used data from the Sloan Digital Sky Survey to conclude that rocky worlds emerge around at least a small percentage of A- and F-class stars. The method: Analyze the position, motion and spectra of white dwarfs found in the SDSS survey. Farihi was interested in the presence of elements heavier than hydrogen and helium in the stellar atmospheres. Finding calcium, magnesium or iron in the atmosphere of a white dwarf is, Farihi believes, evidence of rocky debris, and the new work shows that at least 3 percent and as much as 20 percent of all white dwarfs may be contaminated in this way. Such elements should have sunk below the photosphere in the high gravity of a white dwarf, leading to the belief that any visible contamination must be the...

The Exoplanets Rising conference, now in progress at the Kavli Institute for Theoretical Physics (UC Santa Barbara), is offering a treasure trove of online material, including one I'm currently watching, a presentation by Magali Deleuil (Astronomy Observatory of Marseilles Provence) on CoRoT results. It's extraordinary for those of us who couldn't be at the conference to have quick access to talks by the likes of Michel Mayor, Lisa Kaltenegger, Geoff Marcy and Debra Fischer on everything from transit puzzles to metallicity trends. Interesting to note that CoRoT is now, according to Deleuil, at the end of the 'nominal lifetime of the instrument,' although CoRoT's extended mission has been approved and the spacecraft will remain in operation until March of 2013. Deleuil says that thirteen observing runs have been completed, totaling 75,000 light curves from 'stares' of more than 60 days and 50,000 light curves from 25-day stares. Since February of 2007, 150 planetary candidates have...

Making discoveries with new space missions always seems frustratingly slow, probably because with missions like Kepler, our expectations are so high. So it's interesting to ponder what all is involved in getting the data analyzed and the discoveries pegged. This post from the Kepler team's Charlie Sobeck points out that the first five planets Kepler found were the result of six weeks of flight data and about 25 days of ground-based observing to eliminate the false positives and determine the mass of the planets and properties of the host stars. Nothing runs as smoothly as we might wish. The Kepler team had to sort through much of the data manually because the data processing software is not yet fully functional at NASA Ames. But word from the site is that a major software upgrade has finished development and can now be applied to analysis of almost a full year of data. It's also worth noting that the Kepler mission is now being managed by Ames rather than the Jet Propulsion...

Claire Moutou, one of an international team of astronomers behind the discovery of the planet CoRoT-9b, says the distant world will become a 'Rosetta stone in exoplanet research.' And perhaps it will, for this is a transiting gas giant, but not a 'hot Jupiter.' In an orbit not dissimilar to that of Mercury, CoRoT-9b transits its star every 95 days, each transit lasting about eight hours. We've identified approximately 70 planets by transit methods, but this one is ten times farther from its host star than most gas giants previously discovered by this technique. We may be jumping the gun a bit to call the climate here 'temperate,' as this European Southern Observatory news release does, because temperatures here will depend on layers of highly reflective clouds that may or may not exist on CoRoT-9b. ESO cites temperatures between 160 degrees and minus twenty degrees Celsius beneath those assumed clouds, but we should be able to learn much more because of the lengthy transit periods....

Want to play around with some numbers? The process is irresistible, and we do it all the time when plugging values into the Drake equation, trying to find ways to estimate how many other civilizations might be out there. But a question that is a bit less complicated is how many terrestrial planets exist in the habitable zones of their stars? It's a question recently addressed by Jianpo Guo (National Astronomical Observatories, Kunming, China) and colleagues via simulations. By 'terrestrial' world, the researchers refer to planets between one and ten Earth masses, although they note that some scientists would take this figure lower, to perhaps 0.3 Earth masses, which may be enough to retain an atmosphere over long geological timescales and to sustain tectonic activity. Guo's team is interested in the distribution of terrestrial planets in our galaxy, and the simulations that grew out of this study create a probability distribution of such planets in habitable zones. The paper is laced...

We've been talking for the last six years (since Centauri Dreams' inception) about finding a terrestrial world in the habitable zone of another star. It's an exciting prospect, but the reality about space missions like Terrestrial Planet Finder and Darwin, each designed to make such identifications, is that the budget ax has fallen and we don't know when they might fly. Indeed, we still face a host of technological difficulties that call for much work if the aim is not only to find a terrestrial world but also to study its atmosphere for possible biomarkers. Alternatives are therefore welcome, and one is to look for terrestrial worlds around nearby red dwarf stars using transit methods. Usefully, an Earth-size planet orbiting such an M dwarf would be easier to spot than the same size planet orbiting a star like the Sun, and we could use 'eclipse spectroscopy' with the James Webb Space Telescope to study such a planet's atmosphere. Right now we're making Doppler surveys of nearby M...

What JPL's Mark Swain calls 'an absolutely brilliant way to characterize super-Earths' has emerged from work performed with a small NASA infrared telescope, one that has allowed scientists to identify an organic molecule in the atmosphere of a distant gas giant. HD 189733b is an old friend by now, the subject of intensive studies with space-based telescopes that have revealed water vapor, methane and carbon dioxide in its atmosphere. In the new work, Swain's team made a spectrographic detection of carbon dioxide and methane using a ground-based instrument and a new method to remove the effects of tracking errors and the variability induced by changes in the Earth's atmosphere. Image: To detect the chemicals in the atmospheres, astronomers measure light from the star system as its planet, which is lined up edge-on from our point of view, orbits around. The total light is measured (B in the chart at lower left), and then, when the planet disappears behind the star, the light of the...

Over twenty percent of the planets we've found around other stars inhabit binary systems. It's intriguing to take a close look at these. Most of the planet-bearing binaries are what is known as 'wide S-types,' meaning that the companion star orbits the inner star/planet system at a distance of over 100 AU. But take a good look at GJ86b, γ Cephei b and HD41004b. Here we're looking at three planets in close binary systems with a separation between the component stars of 20 AU or less. That separation raises the eyebrows, for Alpha Centauri A and B form a close binary with a semimajor axis of 23.4 AU. We have three ongoing planet hunts around the Centauri stars, Debra Fischer's work being matched by Michel Mayor's team at La Silla and both complemented by a new search based at Mt. John Observatory in New Zealand. So it may not be long -- months, possibly -- before we have some word about planets around these stars. Informing all these searches, though, is the issue of...

Astronomers have obtained a direct spectrum of the exoplanet HR 8799 c, about 130 light years from Earth, and if you watch your definitions, it's possible to call this the first 'direct spectrum' of such a world. I throw in the qualifier because way back in 2004, astronomers using the ESO's Very Large Telescope and the infrared instrument NACO obtained an image and a spectrum of a planet of about five Jupiter masses around a brown dwarf. The question then involved how the two objects formed -- did they form together, like a stellar binary, or did the smaller object form out of the disk around the brown dwarf? Whatever the case, the new work on HR 8799, also conducted with the VLT and NACO, takes us into interesting territory. Up until now, the way we've obtained a spectrum from an exoplanet has been to observe the planet moving directly behind its host star. The spectrum was then derived by comparing the light from the star before and after this event. That method relies, of course,...

Glints of light off oceans or ice caps would be useful indeed as we try to figure out what we're seeing on a distant terrestrial world. One day we'll have the kind of instrumentation that can make direct observations of a planet like this, separating its light from that of its star. A 'terrestrial planet finder' mission that finds sun glints in its data would have identified a planet that could be suitable for life, one with large areas of water or ice. Drake Deming (NASA GSFC) specializes in recognizing features like this in his work as deputy principal investigator for the Extrasolar Planet Observations and Characterization (EPOCH) study, a part of the extended mission of the Deep Impact spacecraft. EPOCH has produced two new videos showing bright flashes produced by sunlight as the Earth is seen to rotate from a distance of about eleven million miles. The idea is to produce a view of the Earth that can be studied in the same way a future planet-hunter spacecraft would study an...