Be aware of Open Source, a radio show on Boston's WBUR that last week did a show about exoplanets and the possibility of extraterrestrial life. Earth 2.0 is available online, featuring David Latham (Harvard-Smithsonian Center for Astrophysics), Dimitar Sasselov (Harvard University), Jason Wright (Penn State) and Sarah Rugheimer (a PhD student at Harvard studying exoplanet atmospheres). The discussion ranges through the Kepler mission to the Fermi question and recent studies of exoplanet atmospheres, the latter particularly appropriate to today's post. For I want to talk today about 'Hot Jupiters' and their atmospheres, and what we can learn about planet formation by studying their composition. Hot Jupiters were a surprise when first discovered, but models of planetary migration seemed to explain them. We would expect a gas giant to form at or beyond the 'snow line,' where volatiles like water would form ice grains. As we saw in our discussion of Kepler-421b (see Transiting World at...

Both the Kepler and Spitzer space telescopes had a role to play in recent work on the planet Kepler-93b, whose size is now known to an uncertainty of a mere 120 kilometers on either side of the planet. What we have here is the most precise measurement of an exoplanet radius yet, a helpful result in the continuing study of 'super-Earths,' a kind of world for which we have no analogue in our own Solar System. A third instrument also comes into play, for studies of the planet's density derived from Keck Observatory data on its mass (about 3.8 times Earth's mass) and the known radius indicate this is likely an world made of iron and rock. And that is absolutely the only similarity between Kepler-93b and Earth, for at 0.053 AU, six times closer than Mercury to the Sun, the planet's surface temperature is estimated to be in the range of 760 degrees Celsius. The planet is 1.481 times the width of Earth. The accuracy of the measurement is the story here, a result so precise that, in the...

It’s 9000 times easier to find a ‘hot Neptune’ than a Neptune out around the ‘snow line,’ that region marking the distance at which conditions are cold enough for ice grains to form in a solar system. Thus says David Kipping (Harvard-Smithsonian Center for Astrophysics), who is lead author on the paper announcing the discovery of Kepler-421b, an interesting world about which Kipping has been sending out provocative tweets this past week. Kepler-421b draws the eye because its year is 704 days, making it the longest orbital period transiting planet yet found. The intriguing new world is located about 1000 light years from Earth in the direction of the constellation Lyra. The transit method works by detecting the characteristic drop in brightness as a planet moves across the face of the star as seen from Earth. What’s unusual here is that Kepler-421b moved across its star only twice in the four years that the Kepler space telescope monitored it. As Kipping explains on this CfA web page,...

Although I'm sure I'll refer to various papers presented at the American Astronomical Society this week in future entries, I'll close our current look at the Boston meeting with word of two planets that will be falling into their star in short order (at least as astronomers measure time). Kepler-56b and Kepler-56c have a predicted era of death, some 130 million and 155 million years from now respectively. I can't think of any other exoplanets about which we've been able to make such statements, making this a system worth watching as we ponder our own Sun's future. Just as the Sun will one day enlarge to red giant status, threatening the inner planets, so Kepler-56 is growing, already reaching four times the size of the Sun. The star has a long way to go as it continues its outward expansion, and the two planets in question are in a perilous position, with Kepler-56b orbiting the host star every 10.5 days, and Kepler-56c every 21.4. Gongjie Li (Harvard-Smithsonian Center for...

On Tuesday I mentioned the work of Lars A. Buchhave, an astronomer at the Harvard-Smithsonian Center for Astrophysics (CfA), in connection with the Kepler-10c discovery. The latter is the so-called ‘mega-Earth’ now found to be seventeen times as massive as our own planet, with a diameter of about 29,000 kilometers. A larger population of solid planets with masses above 10 times that of Earth was suggested in the Kepler-10c paper (see Introducing the ‘Mega-Earth’ for more on this), with reference to Buchhave’s ongoing work. Let’s take a closer look at what Buchhave is doing, because the intriguing fact is that planets four times the size of Earth and smaller comprise about three-quarters of the planets found by the Kepler mission. How large a role does the metallicity of the host star play in planet formation? At the ongoing meeting of the American Astronomical Society in Boston, Buchhave explained his research methods, which involve measuring ‘metals’ -- in astronomical parlance the...

The red dwarf known as Kapteyn's Star -- the name comes from the 19th Century Dutch astronomer Jacobus Kapteyn -- is about thirteen light years from Earth in the southern constellation of Pictor, close enough that a small telescope can pick it out. Kapteyn's efforts at cataloguing the star in 1898 revealed that it had the highest proper motion of any star then known, a position it lost with the discovery of Barnard's Star in 1916. Because I find stellar encounters interesting, I'll note that about 11,000 years ago, Kapteyn's Star would have come within seven light years of the Sun. It has been moving away from us ever since. Kapteyn's Star belongs to the galactic halo, a dispersed population of stars on elliptical orbits that wraps around the galactic disk and bulge. It is the nearest known halo star to the Sun. We now know, through the efforts of an international research team, that at least two planets are found here. Kapteyn c is a 'super-Earth' with an orbit of 121 days, while...

Building public interest in deep space is a long-term goal for most of us in the interstellar community, and the release of the film Interstellar this fall may set off a new round of discussion among reviewers and movie fans alike. Also helpful is the DVD release of the Neil deGrasse Tyson Cosmos series, given Tyson’s performance and the stunning visuals that communicate the majesty and power of the universe around us. But I think it’s encouraging that while these blockbuster media releases work their magic, what used to be staid scientific conferences frequented only by specialists are turning into media events of their own. The American Astronomical Society is currently meeting in Boston, with exoplanet papers that I’m already seeing discussed well outside the usual venues. The more we see the excitement and sheer scope of the exoplanet hunt communicated to the public, the more likely we’re building the kind of interest among young people that may one day turn into scientific...

Given the high quality imagery returned by Cassini on an almost routine basis, it's interesting to remember how little we knew about Saturn's moon Titan back in November of 1980, when Voyager 1 made its closest approach to the planet. Think of the options the Voyager 1 team had in front of it. The craft could have been sent on to Uranus and Neptune, a trek Voyager 2 would later accomplish. It could have preempted New Horizons if, on a different trajectory, it had been sent to Pluto. But Titan had the allure of a thick atmosphere, making it an irresistible target. Deflecting Voyager 1 past Titan meant taking it out of the plane of the ecliptic, canceling the other two options, and the frustration of the Titan images the spacecraft returned is summed up in the view we see at the right, a moon whose surface is completely obscured. The visually impenetrable atmosphere was also found to be topped by a thick layer of haze. Learning about that atmosphere was hugely important for planetary...

A friend asked me the other day whether my interest in exomoons -- moons around exoplanets -- wasn't just a fascination with the technology of planet hunting. After all, we've finally gotten to the point where we can detect and confirm planets around other stars. An exomoon represents the next step at pushing our methods, and a detection would be an affirmation of just how far new technology and ingenious analysis can take us. So was there really any scientific value in finding exomoons, or was the hunt little more than an exercise in refining our tools? I've written about technology for a long time, but the case for exomoons goes well beyond what my friend describes. We've found not just gas giants but 'super-Earths' in the habitable zones of other stars, and it's a natural suggestion that around one or both classes of planet, an exomoon might he habitable even if the parent world were not. It's a natural assumption that moons exist around other planets elsewhere as readily as they...

Given how many planet-hosting stars we’re finding, any markers that can tell us which are most likely to have terrestrial worlds would be welcome. New work out of Vanderbilt University is now providing us with an interesting possibility. Working with the university’s Keivan Stassun, graduate student Trey Mack has developed a model that studies the chemical composition of a given star and relates it to the amount of rocky material it has ingested during the course of its lifetime. Stars with a high amount of such material may be places where small, terrestrial worlds are rare. What Mack has done is to look at the relative abundance of fifteen specific elements. According to this Vanderbilt news release, he was most interested in elements with high condensation temperatures like aluminum, silicon, calcium and iron, the kind of materials that become building blocks for planets like the Earth. In this context, it’s important to remember that stars are 98 percent hydrogen and helium, with...

How do you go about characterizing a directly imaged planet around another star? In the absence of a transit, one way is to apply theoretical models of planetary formation and evolution to the light spectrum you're working with. When a team of researchers led by Marie-Ève Naud (a graduate student at the Université de Montréal) used these methods on direct imaging data from four different observatories to characterize a planet 155 light years from the Earth, they arrived at a temperature of some 800 degrees Celsius. The work drew inferences based upon the location of the newly detected world. For the planet, GU Piscium b, orbits a star that is a member of the AB Doradus moving group, some 30 stars that move together with the star AB Doradus. The AB Doradus association is helpful because a moving group is made up of stars of roughly the same age and metallicity, a sign they probably formed in the same location. The fact that these are young stars, perhaps 100 million...

Anyone who follows this site is well aware of David Kipping's work as Principal Investigator of The Hunt for Exomoons with Kepler, which sifts through the voluminous Kepler data in search of exoplanet satellites. Now based at the Harvard-Smithsonian Center for Astrophysics (CfA), David lists a number of research interests including the study and characterization of transiting exoplanets, the development of novel detection and characterization techniques, exoplanet atmospheres, Bayesian inference, population statistics and starspot modeling. Yesterday he wrote with news that will get the attention of anyone interested in stars near the Sun. A transit search of Proxima Centauri, never before attempted, is about to begin. By David Kipping I wanted to let Centauri Dreams readers know that I'm leading an upcoming observing campaign with MOST this month and the mission's PI, Jaymie Matthews, recently shared with us an important decision by the Canadian Space Agency (CSA) on May 1st which...

Writing yesterday about Kevin Luhman’s discovery of another cold brown dwarf in the stellar neighborhood reminded me of work we discussed earlier this year in which the weather on the surface of Luhman 16 B was mapped. This was done using the European Southern Observatory’s Very Large Telescope (see Focus on the Nearest Brown Dwarfs), which found variations in the brightness of one of the two dwarfs in this interesting binary just six light years from the Sun. We are beginning, in other words, to chart features in the atmosphere of a brown dwarf whose atmosphere is 1100 degrees Celsius and filled with molten iron and minerals. With that in mind, the news that Dutch astronomers also using the Very Large Telescope (with the CRIRES spectrograph) had measured the rotation rate of an exoplanet immediately caught my eye. Beta Pictoris b orbits its primary some 63 light years from Earth in the constellation Pictor (The Painter’s Easel). It was one of the first exoplanets to be directly...

Kevin Luhman (Pennsylvania State University) has focused much of his research on the formation of low-mass stars and brown dwarfs in star-forming regions near the Sun. This involves working with relatively young stars, but Luhman is also on the alert for older objects, very cool brown dwarfs in the solar neighborhood. Brown dwarfs cool over time, and as Luhman describes on his university web page, they are ‘valuable laboratories for studying planetary atmospheres.’ They also give us a chance to test theories of planet formation in extreme environments. Now we have Luhman’s latest, and it would not be a surprise if the whole category of nearby, cool stellar objects begins to get referred to as ‘Luhman objects’ or some such. Remember that it was just back in March that the astronomer discovered, using WISE images, a binary brown dwarf system at a scant 6.5 light years from Earth. The new find is WISE J085510.83-071442.5. It has the third highest proper motion and the fourth largest...

We're developing a model for the fascinating planetary system around the binary star 55 Cancri, a challenging task given the complexity of the inner system in particular. What we have here is a G-class star around which five planets are known to orbit and a distant M-dwarf at over 1000 AU. Have a look at the diagram below and you'll see why the system, 39 light years away in the constellation Cancer, draws so much attention. It's much more than the fact that direct measurements of the G-class star's radius are possible at this distance, which have led to precise measurements of its mass, about the same as our Sun. It's also the tightly packed configuration of the inner planets. Image: An illustration of the orbital distances and relative sizes of the four innermost planets known to orbit the star 55 Cancri A (bottom) in comparison with planets in own inner Solar System (top). Both Jupiter and the Jupiter-mass planet 55 Cancri "d" are outside this picture, orbiting their host star...

Gravitational lensing is a technique rich enough to help us study not only distant galaxies but exoplanets around stars in our own Milky Way. As gravity warps space and time, light passing near a massive object takes the shortest route, from our perspective seeming to be bent by the gravitational field. Inside the Milky Way, such effects are referred to as 'microlensing,' capable of magnifying the light of a more distant object and sometimes revealing the presence of an unseen planet around the intervening star. Now we have a Kepler find with implications for binary stars. Working with Eric Agol at the University of Washington, graduate student Ethan Kruse has discovered a 'self-lensing' white dwarf eclipsing binary system. He made the find while looking for transits in the Kepler data, the signatures of planets crossing in front of their stars as seen from Earth. KOI-3278 turned out to have an unusual signal, says Kruse: "I found what essentially looked like an upside-down planet....

Last week's announcement about Kepler-186f presented a world that is evidently in the outer reaches of its star's habitable zone, with the usual caveats that we know all too little about this place to draw any conclusions about what is actually on its surface. Is it rocky, and does it have liquid water? Perhaps, but as Greg Laughlin (UC-Santa Cruz) points out on his systemic site, the widely circulated image of Kepler-186f was all but photographic in its clarity. Listen to Laughlin as he looks at the image: I stared at it for a long time, tracing the outlines of the oceans and the continents, surface detail vivid in the mind's eye. Yes, ice sheets hold the northern regions of Kepler-186f in an iron, frigid grip, but in the sunny equatorial archipelago, concerns of global warming are far away. Waves lap halcyon shores drenched in light like liquid gold. He goes on to look at how the press has handled earlier stories on habitable planets, dating back to the Gliese 581c frenzy of 2007....

Gravitational microlensing is a phenomenally interesting way to find unusual things in the cosmos. A closer star can bend space around itself enough that, when it passes between us and a more distant star, a distinct brightening of the distant star's light is apparent, a lens effect. That's a useful phenomenon in its own right, and gravitational lensing involving distant galaxies is a significant part of some astronomers' toolkits. But we can also use the effect when looking for exoplanets, and in the case of recent work, even a candidate for an exoplanet's moon. The method works in this context because if the foreground star has a planet orbiting it, a second lensing event can occur, and a comparison between the two brightening events can help us figure out the relative mass of the two objects. The problem with microlensing is that these are one-shot events, dependent on chance celestial alignments. In other words, we can't go back and study them a second time. That's a shame,...

When it comes to habitable planets, we focus naturally enough on stars like our own. But increasing attention has been paid to stars smaller and cooler than the Sun. M-class dwarfs have small but interesting habitable zones of their own and certain advantages when it comes to detecting terrestrial planets. K-class stars are also interesting, with a prominent candidate, Alpha Centauri B, existing in our stellar back yard. What we haven't examined with the same intensity, though, are stars a bit more massive and hotter than the Sun, and new work suggests that this is a mistake. Manfred Cuntz (University of Texas at Arlington), working with grad student Satoko Sato, has been leading work on F-class stars of the kind normally thought problematic for life because of their high levels of ultraviolet radiation. Along with researchers from the University of Guanajuato (Mexico), Cuntz and Sato suggest that we take a closer look at F stars, particularly considering that they offer a wider...

This morning I want to circle around to a story I had planned to write about a couple of weeks ago. One thing writing Centauri Dreams has taught me is that there is never a shortage of material, and I occasionally find myself trying to catch up with stories long planned. In this case, the imaging of an exoplanet around the star Beta Pictoris demands our attention because of the methods used, which involve charge-coupled devices and wavelengths close to visible light. The detection marks real progress in visible light imaging of exoplanets. The work, which is slated to appear in The Astrophysical Journal, was conducted by researchers from the University of Arizona led by Laird Close. Charge-coupled devices (CCD) are the same kind of technology we find in digital camera imaging sensors, used here in a setting where we’d normally expect an infrared detector. But using infrared means viewing massive young planets hot enough to put out considerable heat. As the exoplanet hunt develops and...