Yesterday's story on the smallest exoplanet yet discovered somewhat obscured work on brown dwarfs released at the same conference. But this year's meeting of the American Astronomical Society has been filled with interesting items, and I don't want to neglect the latest news about a type of star that may be as plentiful as any in the cosmos. We don't know that that is the case, but we have much to learn about brown dwarfs as we compile a census of those in the Sun's neighborhood, including the question of what kind of planets might circle them. New observations studied by Michael Liu (University of Hawaii) and team have now been able to determine the masses of a number of brown dwarfs, with findings that suggest the shape of future research. Says Liu: "Mass is the fundamental parameter that governs the life-history of a free-floating object, and thus after many years of patient measurements, we are delighted to report the first masses of the very faintest, coldest brown dwarfs. After...

Smaller and smaller planets keep coming into view. A prime goal, of course, is to find something around the size of the Earth, implying as it would the existence of a world that might be like ours in other ways. My suspicion is that one day soon a transit study is going to come up with an exoplanet that's closer to the size of Mars (definitely possible with today's technologies), and we'll skip right past the 'Earth twin' point before finding a planet that really is close to the same diameter. But so far we're still looking at worlds larger than Earth, like the tongue-twisting MOA-2007-BLG-192Lb, now thought to be the lowest mass planet ever found around another star. Announced today at the American Astronomical Society's meeting in St. Louis, the new planet orbits a brown dwarf. At six percent of the mass of the Sun (and thus unable to sustain nuclear reactions in its core), the host is the lowest mass star to have a companion with a planetary mass ratio. But the fudge factor in the...