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TOPIC: Extrasolar Planets
Blobrana


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RE: Extrasolar Planets
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Title: Planet formation around stars of various masses: Hot super-Earths
Authors: Grant M. Kennedy, Scott J. Kenyon

We consider trends resulting from two formation mechanisms for short-period super-Earths: planet-planet scattering and migration. We model scenarios where these planets originate near the snow line in ``cold finger'' circumstellar disks. Low-mass planet-planet scattering excites planets to low periastron orbits only for lower mass stars. With long circularisation times, these planets reside on long-period eccentric orbits. Closer formation regions mean planets that reach short-period orbits by migration are most common around low-mass stars. Above ~1 Solar mass, planets massive enough to migrate to close-in orbits before the gas disk dissipates are above the critical mass for gas giant formation. Thus, there is an upper stellar mass limit for short-period super-Earths that form by migration. If disk masses are distributed as a power law, planet frequency increases with metallicity because most disks have low masses. For disk masses distributed around a relatively high mass, planet frequency decreases with increasing metallicity. As icy planets migrate, they shepherd interior objects toward the star, which grow to ~1 Earth mass. In contrast to icy migrators, surviving shepherded planets are rocky. Upon reaching short-period orbits, planets are subject to evaporation processes. The closest planets may be reduced to rocky or icy cores. Low-mass stars have lower EUV luminosities, so the level of evaporation decreases with decreasing stellar mass.

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Blobrana


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GJ 436c
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Spanish and UCL (University College London) scientists have discovered a possible terrestrial-type planet orbiting a star in the constellation of Leo. The new planet, which lies at a distance of 30 light years from the Earth, has a mass five times that of our planet but is the smallest found to date. One full day on the new planet would be equivalent to three weeks on Earth.

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Blobrana


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Posts: 131433
Date:
RE: Extrasolar Planets
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Spanish and UCL (University College London) scientists have discovered a possible terrestrial-type planet orbiting a star in the constellation of Leo. The new planet, which lies at a distance of 30 light years from the Earth, has a mass five times that of our planet but is the smallest found to date. One full day on the new planet would be equivalent to three weeks on Earth.
The team of astronomers from the Spanish Research Council (CSIC) working with Dr Jean-Philippe Beaulieu, a visiting astrophysicist at UCL, made the discovery from model predictions of a new exoplanet (meaning planet outside our solar system) orbiting a star in the constellation of Leo. Simulations show that the exoplanet, dubbed GJ 436c, orbits its host star (GJ 436) in only 5.2 Earth days, and is thought to complete a revolution in 4.2 Earth days, compared to the Earths revolution of 24 hours and full orbit of 365 days. On Earth, a full day (sunset to sunset) coincides quite closely with the rotation period. On the new planet these two periods do not coincide, since the orbital translation period and the rotation period are very similar. For this reason, a full day on the new planet would take four planetary years, or roughly 22 Earth days.

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Blobrana


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OGLE-TR-211b
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Title:  OGLE-TR-211 - a new transiting inflated hot Jupiter from the OGLE survey and ESO LP666 spectroscopic follow-up program
Authors: A. Udalski, F. Pont, D. Naef, C. Melo, F. Bouchy, N. C. Santos, C. Moutou, R. F. Díaz, W. Gieren, M. Gillon, S. Hoyer, M. Mayor, T. Mazeh, D. Minniti, G. Pietrzynski, D. Queloz, S. Ramirez, M. T. Ruiz, A. Shporer, O. Tamuz, S. Udry, M. Zoccali, M. Kubiak, M. K. Szymanski, I. Soszynski, O. Szewczyk, K. Ulaczyk, and L. Wyrzykowski

We present results of the photometric campaign for planetary and low-luminosity object transits conducted by the OGLE survey in the 2005 season (Campaign #5). About twenty of the most promising candidates discovered in these data were subsequently verified spectroscopically with the VLT/FLAMES spectrograph. One of the candidates, OGLE-TR-211, reveals clear changes of radial velocity with a small amplitude of 82 m/s, varying in phase with photometric transit ephemeris. Further analysis confirms the planetary nature of this system. Follow-up precise photometry of OGLE-TR-211 with VLT/FORS, together with radial velocity spectroscopy, supplemented with high-resolution, high S/N VLT/UVES spectra allowed us to derive parameters of the planet and host star. OGLE-TR-211b is a hot Jupiter orbiting an F7-8 spectral type dwarf star with a period of 3.68 days. The mass of the planet is equal to 1.03 ±0.20 Jupiter masses, while its radius  1.36 Jupiter radius. The radius is about 20% larger than the typical radius of hot Jupiters of similar mass. OGLE-TR-211b is, then, another example of inflated hot Jupiters - a small group of seven exoplanets with large radii and unusually low densities - objects that are a challenge to the current models of exoplanets.

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Blobrana


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RE: Extrasolar Planets
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Le spectrographe SOPHIE(1) instrument de haute précision de l'Observatoire de Haute-Provence (CNRS-INSU), vient de mettre en évidence l'existence de 5 nouvelles planètes extrasolaires. Leur particularité : ces 5 planètes transitent devant leur étoile... et dans certains cas, leurs caractéristiques interrogent les scientifiques.

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Blobrana


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HAT-P-7b
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Planet HAT-P-7b, spotted about a thousand light years away by a network of small telescopes called HATNet, orbits at only 5.6 million kilometres from its star - around one-tenth of the distance between Mercury and our sun.
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Blobrana


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The word on the street says that methane was  detected in the gas giant atmosphere of  HD 189733b, that is located  in the constellation Vulpecula.
Astronomers Mark Swain and Gautam Vasisht of Caltech in Pasadena, US, and Giovanna Tinetti of University College London, UK, used the Hubble Space Telescope to observe the giant planet that  lies 63 light years from Earth.

Position (J2000):      R.A. 20h 00m 43s.72 Dec. +22° 42' 38".6

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Blobrana


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NASA will hold a media teleconference at 2 p.m. EDT on Wednesday, March 19, to report on the first-ever detection of the organic molecule methane in the atmosphere of a planet orbiting a distant star.

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Blobrana


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Title: The exoplanet-host star iota Horologii: an evaporated member of the primordial Hyades cluster
Authors: S. Vauclair, M. Laymand, F. Bouchy, G. Vauclair, A. Hui Bon Hoa, S. Charpinet, M. Bazot

We show that the exoplanet-host star iota Horologii, alias HD17051, which belongs to the so-called Hyades stream, was formed within the primordial Hyades stellar cluster and has evaporated towards its present location, 40 pc away. This result has been obtained unambiguously by studying the acoustic oscillations of this star, using the HARPS spectrometer in La Silla Observatory (ESO, Chili). Besides the fact that iota Hor belongs to the Hyades stream, we give evidence that it has the same metallicity, helium abundance, and age as the other stars of the Hyades cluster. They were formed together, at the same time, in the same primordial cloud. This result has strong implications for theories of stellar formation. It also indicates that the observed overmetallicity of this exoplanet-host star, about twice that of the Sun, is original and not caused by planet accretion during the formation of the planetary system.

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Blobrana


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Title: CHARA Array Measurements of the Angular Diameters of Exoplanet Host Stars
Authors: Ellyn K. Baines, Harold A. McAlister, Theo A. ten Brummelaar, Nils H. Turner, Judit Sturmann, Laszlo Sturmann, P. J. Goldfinger, Stephen T. Ridgway

We have measured the angular diameters for a sample of 24 exoplanet host stars using Georgia State University's CHARA Array interferometer. We use these improved angular diameters together with Hipparcos parallax measurements to derive linear radii and to estimate the stars' evolutionary states.

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