* Astronomy

The Milky Way Contains at Least 100 Billion Planets

Our Milky Way galaxy contains a minimum of 100 billion planets according to a detailed statistical study based on the detection of three extrasolar planets by an observational technique called microlensing.
Kailash Sahu, of the Space Telescope Science Institute in Baltimore, Md., is part of an international team reporting today that our galaxy contains a minimum of one planet for every star on average. This means that there is likely to be a minimum of 1,500 planets within just 50 light-years of Earth.
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Title: Warm Spitzer Photometry of XO-4b, HAT-P-6b and HAT-P-8b
Authors: Kamen O. Todorov, Drake Deming, Heather A. Knutson, Adam Burrows, Pedro V. Sada, Nicolas B. Cowan, Eric Agol, Jean-Michel Desert, Jonathan J. Fortney, David Charbonneau, Gregory Laughlin, Jonathan Langton, Adam P. Showman, Nikole K. Lewis

We have analysed Warm Spitzer/IRAC observations of the secondary eclipses of three planets, XO-4b, HAT-P-6b and HAT-P-8b. We measure secondary eclipse amplitudes at 3.6{\mu}m and 4.5{\mu}m for each target. XO-4b exhibits a stronger eclipse depth at 4.5{\mu}m than at 3.6{\mu}m, which is consistent with the presence of a temperature inversion. HAT-P-8b shows a stronger eclipse amplitude at 3.6{\mu}m, and is best-described by models without a temperature inversion. The eclipse depths of HAT-P-6b can be fitted with models with a small or no temperature inversion. We consider our results in the context of a postulated relationship between stellar activity and temperature inversions and a relationship between irradiation level and planet dayside temperature, as discussed by Knutson et al. (2010) and Cowan & Agol (2011), respectively. Our results are consistent with these hypotheses, but do not significantly strengthen them. To measure accurate secondary eclipse central phases, we require accurate ephemerides. We obtain primary transit observations and supplement them with publicly available observations to update the orbital ephemerides of the three planets. Based on the secondary eclipse timing, we set upper boundaries for e cos(\omega) for HAT-P-6b, HAT-P-8b and XO-4b and find that the values are consistent with circular orbits.

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Title: Know the Star, Know the Planet. II. Speckle Interferometry of Exoplanet Host Stars
Authors: Brian D. Mason, William I. Hartkopf, Deepak Raghavan, John P. Subasavage, Lewis C. Roberts Jr., Nils H. Turner, Theo A. ten Brummelaar

A study of the host stars to exoplanets is important to understanding their environment. To that end, we report new speckle observations of a sample of exoplanet host primaries. The bright exoplanet host HD 8673 (= HIP 6702) is revealed to have a companion, although at this time we cannot definitively establish the companion as physical or optical. The observing lists for planet searches and for these observations have for the most part been pre-screened for known duplicity, so the detected binary fraction is lower than what would otherwise be expected. Therefore, a large number of double stars were observed contemporaneously for verification and quality control purposes, to ensure the lack of detection of companions for exoplanet hosts was valid. In these additional observations, ten pairs are resolved for the first time and sixty pairs are confirmed. These observations were obtained with the USNO speckle camera on the NOAO 4m telescopes at both KPNO and CTIO from 2001 to 2010.

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New planets feature young star and twin Neptunes

An international team, including Oxford University scientists, has discovered ten new planets. Amongst them is one orbiting a star perhaps only a few hundred million years old, twin Neptune-sized planets, and a rare Saturn-like world.
The planets were detected using the CoRoT (Convection, Rotation and Transits) space telescope, 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.
The new finds were announced on 14 June at the Second CoRoT Symposium, held in Marseille.
Out of the ten new exoplanets (CoRoT-16b through to 24b and c) seven are hot Jupiters some of which are unusually dense and/or on unusually elongated orbits, and one is in orbit around an unusually young star. The announcement also includes a planet slightly smaller than Saturn, and two Neptune-sized planets orbiting the same star.
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