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Blobrana


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GJ 436b
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Researchers Discover Surprising Exoplanetary Atmosphere

A Neptune-sized exoplanet orbiting a small star about 33 light years away could be a key stepping stone on the path to making sense of an Earth twin.
The finding is the latest advance in the quest to measure Earth-like planets that could possibly host signs of life, which researchers expect to find in the next few years.
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Ed ~ This may be a big news story. ie Could this be an alien biosignature or indicator of life?

-- Edited by Blobrana on Wednesday 21st of April 2010 07:46:56 PM

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Blobrana


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"It's a big puzzle, Models tell us that the carbon in this planet should be in the form of methane. Theorists are going to be quite busy trying to figure this one out"- Kevin Stevenson, a planetary sciences graduate student at the University of Central Florida in Orlando, lead author of a study.

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Blobrana


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NASA's Spitzer Space Telescope has discovered something odd about a distant planet -- it lacks methane, an ingredient common to many of the planets in our solar system.
The discovery brings astronomers one step closer to probing the atmospheres of distant planets the size of Earth. The methane-free planet, called GJ 436b, is about the size of Neptune, making it the smallest distant planet that any telescope has successfully "tasted," or analysed. Eventually, a larger space telescope could use the same kind of technique to search smaller, Earth-like worlds for methane and other chemical signs of life, such as water, oxygen and carbon dioxide.
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Blobrana


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Gliese 436b
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Title: A Quasi-Stationary Solution to Gliese 436b's Eccentricity
Authors: Konstantin Batygin, Gregory Laughlin, Stefano Meschiari, Eugenio Rivera, Steve Vogt, Paul Butler

We investigate the possibility that the large orbital eccentricity of the transiting Neptune-mass planet Gliese 436b is maintained in the face of tidal dissipation by a second planet in the system. We find that the currently observed configuration can be understood if Gliese 436b and a putative companion have evolved to a quasi-stationary fixed point in which the planets' orbital apses are co-linear and in which secular variations in the orbital eccentricities of the two planets have been almost entirely damped out. We adopt an octopole-order secular theory based on a Legendre expansion in the semi-major axis ratio to delineate well-defined regions of (P_c, M_c, e_c) space that can be occupied by a perturbing companion. We incorporate the evolutionary effect of tidal dissipation into our secular model of the system, and solve the resulting initial value problems for a large sample of the allowed configurations. We then polish the stationary configurations derived from secular theory with full numerical integrations. We present our results in the form of candidate companion planets to Gliese 436b. For these candidates, radial velocity half-amplitudes, K_c, are of order 3 m/s, and the maximum amplitude of orbit-to-orbit transit timing variations are of order Delta t=1 s to Delta t=5s. For the particular example case of a perturber with orbital period, P_c=40 d, mass, M_c=8.5 M_Earth, and eccentricity, e_c=0.58, we confirm our semi-analytic calculations with a full numerical 3-body integration of the orbital decay that includes tidal damping and spin evolution. Additionally, we discuss the possibility of many-perturber stationary configurations, utilizing modified Laplace-Lagrange secular theory.

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Blobrana


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GL 436b
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Title: Transit Timing Observations of the Extrasolar Hot-Neptune Planet GL 436b
Authors: Guy S. Stringfellow, Jeffrey L. Coughlin, Mercedes López-Morales, Andrew C. Becker, Tom Krajci, Fabio Mezzalira, Eric Agol

Gliese 436 is an M dwarf with a mass of 0.45 Msun and hosts the extrasolar planet GL 436b, which is currently the least massive transiting planet with a mass of ~23.17 Mearth, and the only planet known to transit an M dwarf. GL 436b represents the first transiting detection of the class of extrasolar planets known as "Hot Neptunes" that have masses within a few times that of Neptune's mass (~17 Mearth) and orbital semimajor axis <0.1 AU about the host star. Unlike most other known transiting extrasolar planets, GL 436b has a high eccentricity (e~0.16). This brings to light a new parameter space for habitability zones of extrasolar planets with host star masses much smaller than typical stars of roughly a solar mass. This unique system is an ideal candidate for orbital perturbation and transit-time variation (TTV) studies to detect smaller, possibly Earth-mass planets in the system. In April 2008 we began a long-term intensive campaign to obtain complete high-precision light curves using the Apache Point Observatory's 3.5-meter telescope, NMSU's 1-meter telescope (located at APO), and Sommers Bausch Observatory's 24" telescope. These light curves are being analysed together, along with amateur and other professional astronomer observations. Results of our analysis are discussed. Continued measurements over the next few years are needed to determine if additional planets reside in the system, and to study the impact of other manifestations on the light curves, such as star spots and active regions.

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