* Astronomy

Blobrana · L

RE: Extrasolar Planets

Blobrana · L

Title: Formation and Evolution of Close-in Planets
Authors: Soko Matsumura, Stanton J. Peale, Frederic A. Rasio

Recent discoveries of several transiting planets with clearly non-zero eccentricities and some large inclinations started changing the simple picture of close-in planets having circular and low-inclination orbits. Two major scenarios to form such planets are planet migration in a disk, and planet--planet interactions combined with tidal dissipation. The former scenario can naturally produce a circular and low-inclination orbit, while the latter implicitly assumes an initially highly eccentric and possibly high-inclination orbit, which are then circularised and aligned via tidal dissipation. We investigate the tidal evolution of transiting planets on eccentric orbits. We show that the current and future orbital evolution of these systems is likely dominated by tidal dissipation, and not by a more distant companion. Although most of these close-in planets experience orbital decay all the way to the Roche limit, there are two characteristic evolution paths for them, depending on the relative efficiency of tidal dissipation inside the star and the planet. We point out that the current observations may be consistent with one of them. Our results suggest that at least some of the close-in planets with non-zero orbital eccentricity may have been formed by tidally circularising an initially eccentric orbit. We also find that even when the stellar spin-orbit misalignment is observed to be small at present, some systems could have had a highly misaligned orbit in the past. Finally, we also re-examine the recent claim by Levrard et. al., who found that all orbital and spin parameters evolve on a similar timescale to orbital decay.

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WASP-8b

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RE: Extrasolar Planets

Blobrana · L

Six new planets discovered

An international team, including Oxford University scientists, has discovered six diverse new planets, from 'shrunken-Saturns' to 'bloated hot Jupiters', as well a rare brown dwarf with 60 times the mass of Jupiter.
The CoRoT (Convection, Rotation and Transits) space telescope is operated by the French space agency CNES. It discovers planets outside our solar system - exoplanets - when they 'transit', that is pass in front of their stars.
Once CoRoT detects a transit, additional observations are made from the ground, using a number of telescopes all over the world. Although astronomers cannot see the planets directly, they use the space- and ground-based data to measure the sizes, masses, and orbits of these new planets precisely. This is why, among all known exoplanets, those with transits yield the most complete information about planet formation and evolution.
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Title: Atmosphere and Spectral Models of the Kepler-Field Planets HAT-P-7b and TrES-2
Authors: David S. Spiegel, Adam Burrows

We develop atmosphere models of two of the three Kepler-field planets that were known prior to the start of the Kepler mission (HAT-P-7b and TrES-2). We find that published Kepler and Spitzer data for HAT-P-7b appear to require an extremely hot upper atmosphere on the dayside, with a strong thermal inversion and little day-night redistribution. The Spitzer data for TrES-2 suggest a mild thermal inversion with moderate day-night redistribution. We examine the effect of nonequilibrium chemistry on TrES-2 model atmospheres and find that methane levels must be adjusted by extreme amounts in order to cause even mild changes in atmospheric structure and emergent spectra. Our best-fit models to the Spitzer data for TrES-2 lead us to predict a low secondary eclipse planet-star flux ratio (~2x10^-5) in the Kepler bandpass. Finally, we consider how the Kepler-band optical flux from a hot exoplanet depends on the strength of a possible extra optical absorber in the upper atmosphere. We find that the optical flux is not monotonic in optical opacity, and the non-monotonicity is greater for brighter, hotter stars.

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Youngest Planet Confirmed

They're not the most awe-inspiring baby pictures, but new infrared images prove the youngest known planet outside our solar system does in fact exist - and that planets can grow up fast - a new study says.
Probably only a few million years young, Beta Pictoris b is already fully formed, despite standard models that say such a planet should take ten million years to reach "adulthood," researchers say. The planet breaks the record once held by the planet BD 20 1790b, which clocked in at 35 million years old.
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Exoplanet Atmospheres

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RE: Extrasolar Planets

Blobrana · L

Nine New Planets

The discovery of nine new planets challenges the reigning theory of the formation of planets, according to new observations by astronomers. Two of the astronomers involved in the discoveries are based at the UC Santa Barbara-affiliated Las Cumbres Observatory Global Telescope Network (LCOGT), based in Goleta, Calif., near UCSB.
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