Aavso paper Session I sunday Sunday, May 22, 2011, 9: 30 am – 12: 00 pm
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406Extrasolar PlanetsPoster SessionEssex Ballroom406.01
ExoplanetSat Constellation Mary Knapp1, R. Jensen-Clem1, S. Seager1, D. Miller1, M. W. Smith1 1MIT. 8:00 AM - 12:00 PM Essex Ballroom ExoplanetSat combines the low cost CubeSat platform with an innovative two-stage attitude control system to detect exoplanets. ExoplanetSat will be capable of detecting transiting Earth-sized planets in the habitable zone of the brightest sun-like stars with a detection threshold of 7σ. After the successful flight of the first ExoplanetSat prototype, the concept for the complete ExoplanetSat constellation is to search for Earth-sized planets around sun-like stars brighter than visual magnitude 8. In order to develop a tractable target star list of a few hundred stars out of the 1000+ bright sun-like stars available, the goal is to choose target stars with the highest probability for transiting planets based on stellar inclination constraints as determined from asteroseismology. The ExoplanetSat Constellation will consist of dozens of 3U, 6U, and larger CubebSat units. 406.02
ExoplanetSat: The Search for Earth-Sized Planets Rebecca Jensen-Clem1, S. Seager1, M. W. Smith1, C. Pong1, M. Knapp1, D. Miller1 1MIT. 8:00 AM - 12:00 PM Essex Ballroom ExoplanetSat combines the low cost CubeSat platform with an innovative two-stage attitude control system to detect exoplanets. ExoplanetSat will be capable of detecting transiting Earth-sized planets in the habitable zone of the brightest sun-like stars with a detection threshold of 7 sigma. The choice of targeting the brightest sun-like stars is motivated by the desire to conduct spectral follow-up observations to determine the habitability of exoplanet candidates. We present the design of the first three-unit ExoplanetSat, which will launch in the next two years under NASA's CubeSat Launch Initiative. 406.03
8:00 AM - 12:00 PM Essex Ballroom The search for exoplanets is an important goal for the astronomy community in the next decade. Direct imaging and spectroscopy of terrestrial planets in the habitable zones of nearby stars has been identified as a key goal by the ASTRO2010 Decadal Survey. However, any flagship-scale exoplanet mission will also have to provide advanced capabilities that are useful to the entire astronomy community. A large aperture, general purpose, UV-Optical-NIR telescope in the 2020 decade will provide an important continuation and expansion of the capabilities currently provided by the Hubble Space Telescope. In this poster, we discuss the compatibility of a starshade with such a telescope. The starshade architecture is very flexible and can accommodate telescopes with a wide range of designs and requirements, partly because starshades levy almost zero requirements on a telescope. This allows the goals of the Exoplanet community to be achieved while maintaining the capabilities of a general purpose astronomical telescope. 406.04
8:00 AM - 12:00 PM Essex Ballroom The detection of Earth-like exoplanets with the radial velocity method requires extreme Doppler precision and long-term stability in order to measure tiny reflex velocities in the host star. Recent planet searches have led to the detection of so called “super-Earths” (up to a few Earth masses) that induce radial velocity changes of about 1 m/s. However, the detection of true Earth analogs requires a precision of 10 cm/s. One of the largest factors limiting Doppler precision is variation in the Point Spread Function (PSF) from observation to observation due to changes in the illumination of the slit and spectrograph optics. Thus, this stability has become a focus of current instrumentation work. Fiber optics have been used since the 1980’s to couple telescopes to high-precision spectrographs, initially for simpler mechanical design and control. However, fiber optics are also naturally efficient scramblers. Scrambling refers to a fiber’s ability to produce an output beam independent of input. Our research is focused on characterizing the scrambling properties of several types of fibers, including circular, square and octagonal fibers. By measuring the intensity distribution after the fiber as a function of input beam position, we can simulate guiding errors that occur at an observatory. Through this, we can determine which fibers produce the most uniform outputs for the severest guiding errors, improving the PSF and allowing sub-m/s precision. However, extensive testing of fibers of supposedly identical core diameter, length and shape from the same manufacturer has revealed the “personality” of individual fibers. Personality describes differing intensity patterns for supposedly duplicate fibers illuminated identically. Here, we present our results on scrambling characterization as a function of fiber type, while studying individual fiber personality. 406.05
On the Frequency of Additional Planets in Short Period Hot Jupiter Systems from Transit Timing Variations Jason Dittmann1, L. Close2, L. Scuderi2 1Harvard Center For Astrophysics, 2University of Arizona. 8:00 AM - 12:00 PM Essex Ballroom The large number of hot Jupiter planets allows one to probe these systems for additional unseen planets via transit timing variations (TTVs). Even relatively small terrestrial planets, when placed in an energetically favorable mean motion resonance (MMR), can cause detectable TTVs with an amplitude of several minutes (Holman and Murray 2005, Agol et al. 2005). In an effort to discover and characterize such companions, we have embarked on a systematic study of known transiting hot Jupiters, utilizing the 1.55 meter Kuiper telescope on Mt. Bigelow to measure multiple individual transits in an observing season to within 30 second precision, and constrain the nature of any planetary companions. Here, we present current and preliminary results on this study, and show that the systems HAT-P-5, HAT- P-6, HAT-P-8, HAT-P-9, WASP-11/HAT-P-10, HAT-P-11, TrES-2, and WASP-10 do not contain small mass companions in MMRs, or moderate mass companions in close enough proximity to induce TTVs on the order of ~ 1.5 minutes. 406.06
8:00 AM - 12:00 PM Essex Ballroom The unprecedented precision and cadence of Kepler photometry has already resulted in a wealth of new candidate planetary systems. However, it has also given us a window into a previously unseen stellar variability regime that tests the ability of software algorithms to identify transits in the astrophysical 'noise'. Using the publicly released Kepler data, we built the PlanetHunters.org Zooniverse web site to take advantage of the natural pattern recognition capabilities of large numbers of citizen scientists. Individuals classify lightcurve variability and mark transits using simple interactive plots on the web site. After one month in operation using only the first 32 days of data, more than 1.1 million light curves were classified and users identified 90 strong potential candidates. Here we present information about 5 unique planet candidates which have undergone extensive testing for false positives and have not been subsequently published by the Kepler team. We have also taken Keck HIRES spectra of the stellar hosts and so provide precise planetary radii and periods as well as improved stellar properties. 406.07
8:00 AM - 12:00 PM Essex Ballroom Title: The Occurrence Rate of Earth Analog Planets Orbiting Sunlike Stars Authors: Joseph Catanzarite and Michael Shao, Jet Propulsion Laboratory, California Institute of Technology Summary Kepler is a space telescope that searches Sun-like stars for planets. Its major goal is to determine eta_Earth, the fraction of Sunlike stars that have planets like Earth. When a planet ‘transits’ or moves in front of a star, Kepler can measure the concomitant dimming of the starlight. From analysis of the first four months of those measurements for over 150,000 stars, Kepler’s science team has determined sizes, surface temperatures, orbit sizes and periods for over a thousand new planet candidates. In this paper, we characterize the period probability distribution function of super-Earths and Neptunes with periods up to 132 days, and find three distinct period regimes. For planets with periods below 3 days the density increases sharply with increasing period; for periods between 3 and 30 days the density rises more gradually with increasing period, and for periods longer than 30 days, the density drops gradually with increasing period. We estimate that 1% to 3% of stars like the Sun are expected to have Earth analog planets, based on the Kepler data release of Feb 2011. The estimate will improve when it is based on the full 3.5 to 6 year Kepler data set. Accurate knowledge of eta_Earth is essential for the planning of future missions that will image and take spectra of Earthlike planets. Our result that Earths are relatively scarce means that a substantial effort will be needed to identify suitable target stars prior to these future missions. 406.08
Inflated Hot Jupiters may not Require Inflated Physics Eduardo L. Martin1, H. Spruit2 1INTA-CSIC Centro de Astrobiologia, Spain, 2Max-Planck-Institut fur Astrophysik, Germany. 8:00 AM - 12:00 PM Essex Ballroom Due to the Darwin instability, hot Jupiters are expected to spiral in and merge with their host stars. The time scale for this spiral-in can be readily calculated for transiting hot Jupiters, but it is subject to uncertainty in the tidal dissipation parameter Q. Using data available for a sample of over one hundred transiting planets, we calculate the time it takes for hot Jupiters to spiral in from their current distance to their host stars. It is found that the spiral in times are strongly correlated with the excess of the planet's radius relative to its equilibrium radius in the sense that larger radius anomalies correspond to shorter spiral in times. An energy source has to be invoked to keep planets inflated longer than their natural cooling time. Irradiation by the host star has been considered but a plausible mechanism to transport the irradiating flux to the planet interior where it is needed for significant inflation has not yet been identified. A 1 Jupiter mass planet needs an thermal energy excess of the order of its gravitational binding energy in order to inflate it by as much as 50 percent. This rules out a source like dissipation of tides in the planet due to nonsynchronous rotation, since the maximum rotational energy of a planet is only a fraction of its binding energy. We propose that the cause of inflation is that the hot Jupiters are young, typically a few hundred Myr. The reason for this youth is hot Jupiter formation in the merger of a binary. The likely binary populations include W~UMa stars (contact binaries) and low mass detached binaries. This scenario also explains other puzzling properties of hot Jupiters, such as their high abundance in orbits close to the host stars and enhanced lithium depletion. Download 2.63 Mb. Share with your friends:
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