Luhman 16AB (otherwise known as WISE J104915.57-531906) holds out quite an allure for those of us hoping to see future exploratory missions to nearby interstellar space. As recounted here in December (see Possible Planet in Nearby Brown Dwarf System), the European Southern Observatory's Henri Boffin has found that this brown dwarf pair is likely home to a previously undetected companion. Bear in mind that we know of no closer brown dwarf; indeed, Luhman 16AB is no more than 6.6 light years out, making it the third closest system to our Sun after Barnard's Star and, of course, Alpha Centauri. We know very little about this putative companion other than Boffin's estimate that its likely mass is between a few Jupiter masses and perhaps as many as 30, but the good news is that the high end of this mass range should offer us an object that can be detected by adaptive optics, given the size of the apparent separation. In any case, radial velocity methods should work nicely here as well,...

Friday's look at habitable zones, and the possibilities of life below the surface or in the atmosphere of an exoplanet, segues naturally into the fascinating notion of 'superhabitable' worlds. René Heller (McMaster University) and John Armstrong (Weber State University) ponder the possibilities in a recent paper for Astrobiology. What if, the scientists ask, our notions of habitability are too closely crafted to our own anthropocentric viewpoint? Could there be planets that are actually more habitable than the Earth? Should the Earth itself be considered, with respect to a broader view of biology, only marginally habitable? The question has important ramifications for how we approach the search for other habitable worlds. We study extremophilic life forms on Earth and question whether conditions even more bizarre than these could still produce life. But Heller and Armstrong reframe the issue: The word 'bizarre' is here to be understood from an anthropocentric point of view....

I'm a great believer in what I might call the 'conventional' habitable zone; i.e., a habitable zone defined by the possibility of liquid water on the surface. The definition is offered not to exclude exotic possibilities like micro-organisms floating in the clouds of Venus or aquatic life deep inside an ice-covered moon like Europa. Rather, it acknowledges that finding life is hard enough without losing our focus. In terms of exoplanets and feasible near-term study, a warm planet with liquid water -- the kind we live on -- would command our immediate attention. But as we look at much broader issues of how life forms, we may indeed learn that our kind of life is but one component of a vast continuum, as recent work out of the University of Aberdeen reminds us. In a new paper published in Planetary and Space Science, researchers tackle the question of life living deep underground. Now the habitable zone starts to broaden, because things get warmer as we go deep. We know of life here on...

Conventional models of planet formation involve core accretion, where dust grains accumulate into protoplanets whose subsequent collisions and interactions produce planets, or gravitational instability, involving a rapid collapse from dense disk debris into a planetary core. But how far from the parent star does planet formation occur? The more we learn about protoplanetary disks, the more questions individual systems pose, as illustrated by the discovery highlighted today. I'm looking at the image of a young star called HD 142527 in the constellation Lupus, some 450 light years from Earth. The T Tauri star, some five million years old, is thought to be of about two solar masses. A team of Japanese astronomers using observations from the Atacama Large Millimeter/submillimeter Array (ALMA) has found an asymmetric ring of dust that appears, based on the density of dust in the densest part of the ring, to be producing planets. A previously discovered inner disk is confirmed by this...

2500 light years from Earth in the constellation of Cancer lies Messier 67, an open star cluster that is now known to be home to at least three planets. The new worlds, found using the HARPS spectrograph on the European Southern Observatory's 3.6-meter instrument at La Silla, come as the result of an observation program covering 88 selected stars in the cluster over a period of six years. The finding is noteworthy because we have so few known planets in star clusters of any kind. Moreover, one of these planets orbits a truly Sun-like star. Image: This wide-field image of the sky around the old open star cluster Messier 67 was created from images forming part of the Digitized Sky Survey 2. The cluster appears as a rich grouping of stars at the centre of the picture. Credit: ESO/Digitized Sky Survey 2 / Acknowledgement: Davide De Martin. I'm cautious about calling anything 'Sun-like' given how loosely that term has been used over the years, but ESO astronomers say the cluster star...

"Weather on Other Worlds" is an observation program that uses the Spitzer Space Telescope to study brown dwarfs. So far 44 brown dwarfs have fallen under its purview as scientists try to get a read on the conditions found on these 'failed stars,' which are too cool to sustain hydrogen fusion at their core. The variation in brightness between cloud-free and cloudy regions on the brown dwarf gives us information about what researchers interpret as torrential storms, and it turns out that half of the brown dwarfs investigated show these variations. Given the chance nature of their orientation, this implies that most, if not all, brown dwarfs are wracked by high winds and violent lightning. The image below could have come off the cover of a 1950's copy of Astounding, though there it would have illustrated one of Poul Anderson's tales with Jupiter as a violent backdrop ("Call Me Joe" comes to mind). Brown dwarfs are, of course, a much more recent find, and in many ways a far more...

As the 223rd meeting of the American Astronomical Society continues in Washington, we're continuing to see activity on the subject of mini-Neptunes and 'super-Earths,' the latter often thought to be waterworlds. Given how fast our picture of planets in this domain is changing, I was intrigued to see that Nicolas Cowan (Northwestern University) and Dorian Abbot (University of Chicago) have come up with a model that allows a super-Earth with active plate tectonics to have abundant water in its mantle and oceans as well as exposed continents. If Cowan and Abbot are right, such worlds could feature a relatively stable climate even if the amount of water there is far higher than Earth. Focusing on the planetary mantle, the authors point to a deep water cycle that moves water between oceans and mantle, a movement made possible by plate tectonics. The Earth itself has a good deal of water in its mantle. The paper argues that the division of water between ocean and mantle is controlled by...

Yesterday's look at the exoplanet KOI-314c showed us a world with a mass equal to the Earth, but sixty percent larger than the Earth in diameter. This interesting planet may be an important one when it comes to studying exoplanet atmospheres, for KOI-314c is a transiting world and we can use transmission spectroscopy to analyze the light that passes through the atmosphere as the planet moves in front of and then behind its star. A space-based observatory like the James Webb Space Telescope should be able to tease useful information out of KOI-314c. But the American Astronomical Society meeting in Washington DC continues, and it's clear that the technique of studying transit timing variations (TTV) is coming into its own as a tool for exoplanet investigation. David Kipping and colleagues use TTV to look for exomoons, and it was during such a search that they discovered KOI-314c. But consider the other AAS news. At Northwestern University, Yoram Lithwick has been measuring the masses...