Misaligned protoplanetary disks in a young binary star system
Nature 511, 7511 (2014). doi:10.1038/nature13521
Authors: Eric L. N. Jensen & Rachel Akeson
Many extrasolar planets follow orbits that differ from the nearly coplanar and circular orbits found in our Solar System; their orbits may be eccentric or inclined with respect to the host star’s equator, and the population of giant planets orbiting close to their host stars suggests appreciable orbital migration. There is at present no consensus on what produces such orbits. Theoretical explanations often invoke interactions with a binary companion star in an orbit that is inclined relative to the planet’s orbital plane. Such mechanisms require significant mutual inclinations between the planetary and binary star orbital planes. The protoplanetary disks in a few young binaries are misaligned, but often the measurements of these misalignments are sensitive only to a small portion of the inner disk, and the three-dimensional misalignment of the bulk of the planet-forming disk mass has hitherto not been determined. Here we report that the protoplanetary disks in the young binary system HK Tauri are misaligned by 60 to 68 degrees, such that one or both of the disks are significantly inclined to the binary orbital plane. Our results demonstrate that the necessary conditions exist for misalignment-driven mechanisms to modify planetary orbits, and that these conditions are present at the time of planet formation, apparently because of the binary formation process.
Following the extensive in-orbit commissioning review and after encountering the unexpected challenges highlighted previously on the blog, Gaia is now ready to begin its science mission.
Read the announcement published today on the ESA Portal: Gaia: 'Go' for science
And for a full quantitative analysis of Gaia’s expected science performance based on the results of commissioning, see: Commissioning review: Gaia ready to start routine operations
Astronomers using the Hubble Space Telescope have gone looking for water vapor in the atmospheres of three planets orbiting stars similar to the Sun and have come up nearly dry. The planets spectroscopically surveyed have only one-tenth to one one-thousandth the amount of water predicted by standard planet-formation theories. The planets are not habitable because they are gaseous and are as big as Jupiter. They lie so much closer to their host star than Jupiter is to our Sun, so their atmospheres are seething between 1,500 and 4,000 degrees Fahrenheit. Nevertheless, this result suggests that some percentage of Earth-size exoplanets may be more deficient in water than predicted. And, water is a necessary prerequisite for life as we know it. The search for water-bearing terrestrial worlds may be more challenging than thought for future space telescopes. And, scientists may have to revisit their theories of planet formation.