NASA Kepler Mission Manager Update 10 July 2012
Since the last update the team has had two science data downlinks. The most recent one on June 27 included a quarterly roll to the summer science attitude. This successfully completed Quarter 13 of flight operations.
Kepler flight operations have continued smoothly. Recently, a change was made to the profile that the spacecraft uses to desaturate, or unwind, the momentum in the wheels. Normally, at the start and end of each quarter, all of the momentum is held in two of the four reaction wheel assemblies, causing the other two to hover at a near zero speed. Operations near zero speed have more jitter, which can be seen in the pointing performance by the very sensitive science instrument. The spacecraft engineers have come up with a clever way to change the target of the desaturation throughout the quarter to prevent operation near zero of any of the wheels and this was implemented this month.
The new release of the Science Operations Center pipeline software, SOC 8.2, successfully completed the verification and validation test phase and will be deployed to operations the first half of July 2012. As noted in a previous update, SOC 8.2 adds features to: (a) improve corrections of the systematic errors in stellar flux time series; (b) improves sensitivity to planetary systems with two transits only; and (c) improves sensitivity to small planets in multiple planet systems.
Several Kepler team members attended the 220th meeting of the American Astronomical Society (AAS) in Anchorage, Alaska in early June where Kepler’s presence was a major part of the meeting. Two days of special sessions were focused on Kepler results – one day concentrated on exoplanets and one day on astrophysics. The Kepler team hosted its first Town Hall that was attended by over 250 meeting participants. At an AAS press conference, lead author Lars Buchhave, Kepler collaborator and an astrophysicist at the Niels Bohr Institute and the Centre for Star and Planet Formation at the University of Copenhagen, presented a result that shows small planets form around stars with a wide range of heavy element content which suggests that small planets may be widespread in our galaxy. This result widens the field of possible systems that could host planets in the habitable zone. The AAS press conference can be viewed here.
During the visit to Anchorage, the team gave a public talk at the Anchorage Science Pub. More than one hundred members from the community, including local media, listened as project scientist and deputy project scientist, Nick Gautier and Steve Howell, presented the latest results from the Kepler mission. You can watch the presentations on the Anchorage Science Pub’s Facebook page.
The Kepler Asteroseismic Science Consortium (KASC) held its fifth annual workshop, hosted by Konkoly Observatory on June 18-22, 2012, in Balatonalmadi, Hungary. One hundred twenty scientists from over 20 countries attended the event, to discuss stellar astrophysics using Kepler data. Many results were shared on the solar-like oscillations of main sequence and red giant stars in addition to the synergies with exoplanet research.
Below are a few highlights from the scientific research presented at the KASC:
* Mixed mode oscillations in red giant stars allow us to separate out the rotation rate of the stellar core and stellar envelope, giving us a detailed look at the internal structure and angular momentum evolution of these evolved stars. Glitches in the acoustic modes (called mode trappings) have been used to measure the depth of the convection zone in solar-like stars. And surprisingly, the primary star (the A component) of Trinity (HD 181068, KIC 5952403, a triply eclipsing hierarchical triple star) is the only known red giant that doesn’t show solar-like oscillation. A possible explanation is the tidal interaction with the companion binary that likely suppresses these oscillations.
* Significant new results were presented in the session on RR Lyrae stars. These seemingly simple radial pulsators show a huge variety of behaviors in Kepler data, indicative of complex nonlinear dynamical systems (chaos, period doubling bifurcations, high-order resonances). Surprisingly, we learned that it only takes three pulsation modes to create complicated light variations and interactions. This has far-reaching consequences for other multi-mode pulsators, such as delta Scuti stars. The discovery of period doubling and the subsequent modeling efforts resulted in a breakthrough in the investigation of the century-old Blazhko-effect (mysterious amplitude and phase modulation) shown by 50% of RR Lyrae stars. We hope that with the help of Kepler the final explanation of one of the greatest puzzles of pulsation theory will be found in the near future. * Frequency modulation (FM) caused by a light travel time effect in a binary system is a powerful new method for finding planetary and stellar companions around pulsating stars. Its importance lies in the fact that multimode pulsators are not suitable for transit or radial velocity search. Similarly, high-mass and rapidly rotating stars are usually not optimal for finding companions by radial velocity surveys. The purely photometric FM-method provides the mass function, the projected orbital distance and the radial velocity curve without spectroscopic observations. We heard about this new method and its applications during the conference.
* M giants represent the late evolutionary stages of sun-like stars. The timescales of their brightness variations are typically on the order of 100 days. Their pulsations are closely linked to mass-loss, a process that is still lacking a deep understanding. Careful analyses of M giant pulsations will help us pinpoint the connection between oscillations, mass-loss and evolution, which, ultimately, will deliver new insight into the future of our own sun. Current Kepler data on M giants are just beginning to scratch the surface, but we expect tremendous improvement with the data promised by the Kepler Extended Mission.
The team also welcomed two new planets to the family. A research team, led by Josh Carter, a Hubble fellow at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., and Eric Agol, a professor of astronomy at the University of Washington in Seattle, discovered a pair of neighboring planets with dissimilar densities orbiting very close to each other. Called Kepler-36b and c, they have the closest-spaced orbits ever confirmed. You can read more about the discoveries in the science literature:
* Kepler-36: A Pair of Planets with Neighboring Orbits and Dissimilar Densities, J Carter et al
* Rapid dynamical chaos in an exoplanetary system, K Deck et al
Meanwhile, the team continues detailed planning for conducting an extended mission. As this planning continues, and will for a few more weeks, the team is preparing to accelerate the release of Kepler mission data to the public archive at the Barbara A. Mikulski Archive for Space Telescopes. On July 28, the team will release Quarters 7, 8, and 9 to the public archive.
