* Astronomy

Blobrana · L

RE: WASP-12b

Blobrana · L

Title: High C/O Ratio and Weak Thermal Inversion in the Very Hot Atmosphere of Exoplanet WASP-12b
Authors: Nikku Madhusudhan, Joseph Harrington, Kevin B. Stevenson, Sarah Nymeyer, Christopher J. Campo, Peter J. Wheatley, Drake Deming, Jasmina Blecic, Ryan A. Hardy, Nate B. Lust, David R. Anderson, Andrew Collier-Cameron, Christopher B. T. Britt, William C. Bowman, Leslie Hebb, Coel Hellier, Pierre F. L. Maxted, Don Pollacco, Richard G. West

The carbon-to-oxygen ratio (C/O) in a planet provides critical information about its primordial origins and subsequent evolution. A primordial C/O greater than 0.8 causes a carbide-dominated interior as opposed to a silicate-dominated composition as found on Earth, and the atmospheres can also differ from those in the Solar System. The solar C/O is 0.54. Here we report an analysis of dayside multi-wavelength photometry of the transiting hot-Jupiter WASP-12b that reveals C/O >= 1 in its atmosphere. The atmosphere is abundant in CO. It is depleted in water vapour and enhanced in methane by over two orders of magnitude each compared to a solar-abundance chemical-equilibrium model at the expected temperatures. We also find that the extremely irradiated atmosphere (T > 2,500 K) of WASP-12b lacks a prominent thermal inversion, or a stratosphere, and has very efficient day- night energy circulation. The absence of a strong thermal inversion is in stark contrast to theoretical predictions for the most highly irradiated hot-Jupiter atmospheres.

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Astronomers find planet with a diamond heart

Scientists may need to rewrite the text books following the discovery of a carbon-rich exoplanet.
The discovery made using the Spitzer Space Telescope poses new questions about how planets are made and how their atmosphere's work.
Reporting in the journal Nature, Dr Nikku Madhusudhan and colleagues from Princeton University, say the planet WASP-12B has an atmosphere with equal parts carbon and oxygen.
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Blobrana · L

It's easy to go just a little nuts when you're studying exoplanets. Spend enough time investigating the exotic chemistry, composition and environments of newly discovered worlds orbiting distant stars and you can start to believe anything's possible. Little, however, can match the fairy-tale possibilities of WASP-12b.
For one thing, there's the heavy concentration of carbon in its atmosphere. For another, there's the potential for methane-loving life. Oh, and did we mention that vast stretches of land could be made of diamonds? O.K., few scientists - actually, no scientists - believe that those precise conditions prevail on WASP-12b. But new findings about the planet's atmosphere do suggest that such an environment is entirely possible on other worlds - perhaps even in WASP-12b's own solar system.
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Blobrana · L

NASA's Spitzer Reveals First Carbon-Rich Planet

Astronomers have discovered that a huge, searing-hot planet orbiting another star is loaded with an unusual amount of carbon. The planet, a gas giant named WASP-12b, is the first carbon-rich world ever observed. The discovery was made using NASA's Spitzer Space Telescope, along with previously published ground-based observations.
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'Diamond exoplanet' idea boosted by telescope find

A US-British team of astronomers has discovered the first planet with ultra-high concentrations of carbon.
The researchers say their discovery supports the idea there may be carbon-rich, rocky planets whose terrains are made up of diamonds or graphite.
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Blobrana · L

Title: WASP-21b: a hot-Saturn exoplanet transiting a thick disc star
Authors: F. Bouchy, L. Hebb, I. Skillen, A. Collier Cameron, B. Smalley, S. Udry, D.R. Anderson, I. Boisse, B. Enoch, C.A. Haswell, G. Hébrard, C. Hellier, Y. Joshi, S.R. Kane, P.F.L. Maxted, M. Mayor, C. Moutou, F. Pepe, D. Pollacco, D. Queloz, D. Ségransan, E.K. Simpson, A.M.S. Smith, H.C. Stempels, R. Street, A.H.M.J. Triaud, R.G. West, P.J. Wheatley

We report the discovery of WASP-21b, a new transiting exoplanet discovered by the Wide Angle Search for Planets (WASP) Consortium and established and characterized with the FIES, SOPHIE, CORALIE and HARPS fibre-fed echelle spectrographs. A 4.3-d period, 1.1% transit depth and 3.4-h duration are derived for WASP-21b using SuperWASP-North and high precision photometric observations at the Liverpool Telescope. Simultaneous fitting to the photometric and radial velocity data with a Markov Chain Monte Carlo procedure leads to a planet in the mass regime of Saturn. With a radius of 1.07 R_Jup and mass of 0.30 M_Jup, WASP-21b has a density close to 0.24 rho_Jup corresponding to the distribution peak at low density of transiting gaseous giant planets. With a host star metallicity [Fe/H] of -0.46, WASP-21b strengthens the correlation between planetary density and host star metallicity for the five known Saturn-like transiting planets. Furthermore there are clear indications that WASP-21b is the first transiting planet belonging to the thick disc.

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The hottest known planet in the Milky Way galaxy may also be its shortest-lived world. The doomed planet is being eaten by its parent star, according to observations made by a new instrument on NASA's Hubble Space Telescope, the Cosmic Origins Spectrograph (COS). The planet may only have another 10 million years left before it is completely devoured.
The planet, called WASP-12b, is so close to its sunlike star that it is superheated to nearly 2,800 degrees Fahrenheit and stretched into a football shape by enormous tidal forces. The atmosphere has ballooned to nearly three times Jupiter's radius and is spilling material onto the star. The planet is 40 percent more massive than Jupiter.
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Blobrana · L

Title: On the Orbit of Exoplanet WASP-12b
Authors: Christopher J. Campo, Joseph Harrington, Ryan A. Hardy, Kevin B. Stevenson, Sarah Nymeyer, Darin Ragozzine, Nate B. Lust, David R. Anderson, Andrew Collier-Cameron, Jasmina Blecic, Christopher B. T. Britt, William C. Bowman, Peter J. Wheatley, Drake Deming, Leslie Hebb, Coel Hellier, Pierre F. L. Maxted, Don Pollaco, Richard G. West

We observed two secondary eclipses of the exoplanet WASP-12b using the Infrared Array Camera on the Spitzer Space Telescope. The close proximity of WASP-12b to its G-type star results in extreme tidal forces capable of inducing apsidal precession with a period as short as a few decades. This precession would be measurable if the orbit had a significant eccentricity. The ground-based secondary eclipse phase reported by Lopez-Morales et al. (0.510 ±0.002) implies eccentricity at the 4.5\sigma level, and the spectroscopic orbit of Hebb et al. has eccentricity 0.049 ±0.015, a 3\sigma result, and predicts an eclipse phase of 0.509 ±0.007. Our eclipse phases are 0.5012 ±0.0006 (3.6 and 5.8 micron) and 0.5007 ±0.0007 (4.5 and 8.0 micron). These values are inconsistent with the ground-based data, but marginally consistent with the spectroscopic orbit. Considering the unlikely possibility that precession brought the long axis of the orbit into alignment during our observations, a model considering these points and transit times from professional and amateur observers estimates orbital precession at \omega = 0.02 ±0.01 deg/d. This implies a tidal Love number, k2p, of 0.15 ±0.08, indicating a very centrally condensed planet. However, if the orbit is actually eccentric, we have observed it at a remarkably special time to find eclipse phases consistent with apsidal alignment. Future observations can decide between these possibilities.

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Title: WASP-12b as a prolate, inflated and disrupting planet from tidal dissipation
Authors: Shu-lin Li (1,2), Neil Miller (3), Douglas N. C. Lin (1,3), Jonathan J. Fortney (3) ((1)Kavli Institude for Astronomy and Astrophysics, Peking University Beijing, (2)Department of Astronomy, Peking University, Beijing, (3)UCSC)

The class of exotic Jupiter-mass planets that orbit very close to their parent stars were not explicitly expected before their discovery. The recently found transiting planet WASP-12b has a mass Mp = 1.4(±0.1) Jupiter masses (MJ), a mean orbital distance of only 3.1 stellar radii (meaning it is subject to intense tidal forces), and a period of 1.1 days. Its radius 1.79(± 0.09) RJ is unexpectedly large and its orbital eccentricity 0.049(±0:015) is even more surprising as such close orbits are in general quickly circularised. Here we report an analysis of its properties, which reveals that the planet is losing mass to its host star at a rate ~ 10^-7 MJ yr^-1. The planets surface is distorted by the stars gravity and the light curve produced by its prolate shape will differ by about ten per cent from that of a spherical planet. We conclude that dissipation of the stars tidal perturbation in the planets convective envelope provides the energy source for its large volume. We predict up to 10mJy CO band-head (2.292 micron) emission from a tenuous disk around the host star, made up of tidally stripped planetary gas. It may also contain a detectable resonant super-Earth, as a hypothetical perturber that continually stirs up WASP-12b's eccentricity.

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