by Wes Traub & Steve Unwin
For those who haven’t tuned in recently, here are some exoplanet news headlines from the last 90 days that most caught our attention:
Three new planet-counting papers appeared since the first of the year. Surprisingly, each of these is moving in the direction of more and more objects out there than we had once thought. First, Cassan et al reported in Nature that microlensing observations suggest that there are, on average, about 1.6 planets per star in the Galaxy. Second, Strigari et al reported their theoretical estimate that there may be up to 100,000 free-floating objects per star (“nomads”) in the Galaxy, where each such object is in the mass range from about the Moon to a brown dwarf. Third, Traub reported in the ApJ that his analysis of the first 136 days of Kepler observations suggests, by extrapolation, that about 34% of FGK stars have a terrestrial planet their habitable zone.
And as proof that some of the new-found objects are interestingly bizarre, three examples of a planet orbiting a binary star have now been discovered, the latest two by Welsh et al as reported in Nature. These are Kepler 16b, 34b, and 35b, with planet masses in the 0.1 to 0.3 Jupiter range, and ratios of planet to star semi-major axes of about 3 to 5. Read about this interesting new class of exoplanets at http://www.nature.com/nature/journal/v481/n7382/full/nature10768.html.
The existence of Fomalhaut b was called into question by Janson et al in the ApJ, as a result of infrared observations which saw no signal where there should have been one if Fomalhaut b were indeed a planet, suggesting that the object seen in the visible is instead a dust cloud. The controversy starts at http://iopscience.iop.org/0004-637X/747/2/116/pdf/apj_747_2_116.pdf.
The Kepler mission won the 2012 Aviation Week Laureate Award in the Space category. Our heroes are featured in the story at http://www.nasa.gov/centers/jpl/news/kepler20120308.html.
Separately, the Kepler team made a successful bid for an extended mission (beyond this fall) at NASA's 2012 Senior Review for Operating Missions. The review panel recommended extending the mission for four years, with a mid-term review in two years to check on progress at that point. This is excellent news, as it means that nearly the entire habitable zone of FGK stars can be searched by Kepler (using the rule that it takes at least 3 transits of a planet before we can be sure of its existence).
The AAS awarded five of this year’s ten prizes to exoplanet scientists, including John Johnson, Eric Ford, Ron Gilliland, Heather Knutson, and Caleb Scharf. See the awards described at
The WFIRST Science Definition Team held several meeting, focusing on proposed science including exoplanet microlensing, and beginning work on a reduced-cost version with a second Design Reference Mission.