‘Planetary mass binary’ is an unusual term, but one that seems to fit new observations of what was thought to be a brown dwarf or free-floating large Jupiter analog, and now turns out to be two objects, each of about 3.7 Jupiter masses. That puts them into planet-range when it comes to mass, as the International Astronomical Union normally considers objects below the minimum mass to fuse deuterium (13 Jupiter masses) to be planets. This is the lowest mass binary yet discovered. A team led by William Best (Institute for Astronomy, University of Hawaii) went to work on the L7 dwarf 2MASS J11193254–1137466 with the idea of determining what they assumed to be the single object’s mass and age. It was through observations with the Keck II telescope in Hawaii that they discovered the binary nature of their target. The separation between the two objects is about 3.9 AU, based upon the assumption that the binary is around 160 light years away, the distance of the grouping of stars called the...

Our theories of planet formation grow more mature as the exoplanet census continues, but I've always speculated about the first planets discovered and how they could have possibly been where we found them. The discovery of the planets around the pulsar PSR B1257+12 occurred in 1992, the work of the Polish astronomer Aleksander Wolszczan. Anomalies in its pulsation period -- this is a millisecond pulsar with a period of 6.22 milliseconds -- led Wolszczan and Dale Frail to produce a paper on the first extrasolar planets ever found. We wouldn't find such planets at all if it were not for the effect of their gravitational pull on the otherwise regular pulses from the pulsar. But how could the planets now know as Draugr, Poltergeist and Phobetor, the latter found in 1994, possibly have formed in such an environment? After all, a dense neutron star (a pulsar is a highly magnetized, rotating neutron star) is the result of a supernova that should have destroyed any planets nearby, making it...

Interesting news keeps coming out of the National Astronomy Meeting in the UK. Today it involves brown dwarfs and their distribution throughout the galaxy, a lively question given how recently we’ve begun to study these ‘failed stars.’ Maybe we need a better name than ‘brown dwarfs,’ for that matter, since these objects are low enough in mass that they cannot sustain stable hydrogen fusion in their core. In a murky intermediary zone between planet and star, they can produce planets of their own but straddle all our contemporary definitions. At the NAS meeting, an international team led by Koraljka Muzic (University of Lisbon) has reported on its work on brown dwarfs in clusters. It seems a sensible approach -- go to the places where young stars are forming and try to figure out how many brown dwarfs emerge alongside them. That could help to give us an overview, because the brown dwarfs we’ve already found (beginning with the first, in 1995) are generally within 1500 light years of...

The prospects for life around M-dwarf stars, always waxing and waning depending on current research, have dimmed again with the release of new work from Christina Kay (NASA GSFC) and colleagues. As presented at the National Astronomy Meeting at the University of Hull (UK), the study takes on the question of space weather and its effect on habitability. We know that strong solar flares can disrupt satellites and ground equipment right here on Earth. But habitable planets around M-dwarfs -- with liquid water on the surface -- must orbit far closer to their star than we do. Proxima Centauri b, for example, is roughly 0.05 AU from its small red host (7,500,000 km), while all seven of the TRAPPIST-1 planets orbit much closer than Mercury orbits the Sun. What, then, could significant flare activity do to such vulnerable worlds? Image: Artist’s impression of HD 189733b, showing the planet’s atmosphere being stripped by the radiation from its parent star. Credit: Ron Miller. Working with...

The European Space Agency has just announced the official adoption of the PLATO mission. The untangled acronym -- PLAnetary Transits and Oscillations of stars -- tells us that, like Kepler and CoRoT, this is a planet hunting mission with asteroseismological implications. Photometric monitoring of nearby bright stars for planetary transits and determination of planetary radii should help build our target list for spectroscopic follow-up as we delve into planetary atmospheres looking for biosignatures. Launch is scheduled for 2026. Asteroseismology studies how stars oscillate, giving us information about the internal structure of the star that would not be available through properties like brightness and surface temperature. PLATO will be carrying out high precision photometric monitoring at visible wavelengths, targeting bright stars (mV ? 11), though with capabilities for fainter stars down to magnitude 16. Several hundred thousand stars will ultimately be characterized in the search...

As announced yesterday at NASA Ames, the Kepler team has released the final Kepler catalog from the spacecraft’s first four years of data and its deep stare into Cygnus. The numbers still impress me despite our having watched them grow with each new report: We have 4034 planet candidates, of which 2335 have been verified as exoplanets. More than 30 of the approximately 50 near-Earth sized habitable zone candidates have been verified. The new release brought us 219 new candidates, 10 of them habitable zone possibilities, giving us a final catalog that is our first take on the prevalence and characteristics of planets in the Milky Way, and paving the way for future space-based instruments as we look for targets for atmospheric characterization and direct imaging. By introducing simulated planet transit signals and adding known false signals, the researchers were able to tighten up the catalog, ensuring against errors in the analysis growing out of the team’s processing methods. The...

The Pale Red Dot campaign that discovered Proxima Centauri b produced one of the great results of exoplanet detection. For many of us, the idea that a world of roughly Earth mass might be orbiting in Proxima Centauri's habitable zone -- where liquid water can exist on the surface -- was almost too good to be true, and it highlighted the real prospect that if we find such a planet around the closest star to our own, there must be many more around similar stars. Hence the importance of learning more about our closest neighbors. Which is why it's so heartening to see that Pale Red Dot is by no means done. This morning, the team led by Guillem Anglada-Escudé (Queen Mary University, London) announced plans to acquire data from the European Southern Observatory's HARPS instrument (High Accuracy Radial velocity Planet Searcher) in a new campaign to study not just Proxima Centauri in search of further planets, but also the red dwarfs Barnard's Star and Ross 154. Also involved will be...