* Astronomy

Astronomers Find Hints of Planetary Pollution

Artist's impression of the structure of a solar-like star and a red giant. The two images are not to scale - the scale is given in the lower right corner. It is common to divide the Sun's (and solar-like stars') interior into three distinct zones: The uppermost is the Convective Zone.

Source


Title: Evolved stars hint to an external origin of enhanced metallicity in planet-hosting stars
Authors: L. Pasquini, M.P. Doellinger, A. Weiss, L. Girardi, C. Chavero, A.P. Hatzes, L. da Silva, J. Setiawan

Exo-planets are preferentially found around high metallicity main sequence stars. We aim at investigating whether evolved stars share this property, and what this tells about planet formation. Statistical tools and the basic concepts of stellar evolution theory are applied to published results as well as our own radial velocity and chemical analyses of evolved stars. We show that the metal distributions of planet-hosting (P-H) dwarfs and giants are different, and that the latter do not favour metal-rich systems. Rather, these stars follow the same age-metallicity relation as the giants without planets in our sample. The straightforward explanation is to attribute the difference between dwarfs and giants to the much larger masses of giants' convective envelopes. If the metal excess on the main sequence is due to pollution, the effects of dilution naturally explains why it is not observed among evolved stars. Although we cannot exclude other explanations, the lack of any preference for metal-rich systems among P-H giants could be a strong indication of the accretion of metal-rich material. We discuss further tests, as well as some predictions and consequences of this hypothesis.

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Astronomers have found water vapour in the atmosphere of a giant planet outside our Solar System.
 HD 189733b orbits a star in the constellation of Vulpecula (the Fox), which is 64 light-years from our Sun.
Although water is a key ingredient for biology, the planet is far too hot to harbour life.
It orbits extremely close to its parent star - more than 30 times closer to its star than the Earth is to the Sun.

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Title: HD147506b: A Super-Massive Planet in an Eccentric Orbit Transiting a Bright Star
Authors: G. A. Bakos, G. Kovacs, G. Torres, D. A. Fischer, D. W. Latham, R. W. Noyes, D. D. Sasselov, T. Mazeh, A. Shporer, R. P. Butler, R. P. Stefanik, J. M. Fernandez, A. Sozzetti, A. Pal, J. Johnson, G. W. Marcy, J. Winn, B. Sipocz, J. Lazar, I. Papp, P. Sari
(Version v2)

We report the discovery of a massive (Mp = 9.04 ±0.50 MJup) planet transiting the bright (V = 8.7) F8 star HD 147506, with an orbital period of 5.63341±0.00013 days and an eccentricity of e = 0.520 ±0.010. From the transit light curve we determine that the radius of the planet is Rp = 0.982^{+0.038}_{0.105}RJup. HD 147506b (also coined HAT-P-2b) has a mass about 9 times the average mass of previously-known transiting exoplanets, and a density of rho = 11.9 g cm-3, greater than that of rocky planets like the Earth. Its mass and radius are marginally consistent with theories of structure of massive giant planets composed of pure H and He, and may require a large (~100 Earth mass) core to account for. The high eccentricity causes a 9-fold variation of insolation of the planet between peri- and apastron. Using follow-up photometry, we find that the centre of transit is Tmid = 2,454,212.8559 ± 0.0007 (HJD), and the transit duration is 0.177 ±0.002 d.

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Extreme Solar Systems III: Even more planets
I'm still working my way through my notes from day 1 of the conference...
did I mention I have a lots of notes.
Actually, by my count, half-way through day 3, I've seen four very interesting announcements that are embargoed, two because of Nature/Science submission issues, which I will of course honour, and two because the people involved asked us not to discuss the results - so I won't;
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