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,...