* Astronomy

Billions of years ago, something kicked planet XO-3b into a ****-eyed orbit. The culprit may have been another planet, which would mean planets can bounce each other around like cosmic billiard balls.
Guillame Hébrard of the Institute of Astrophysics in Paris and colleagues detected an unusual colour shift as XO-3b passed in front of its star. The pattern suggests that its 3.2-day orbit is tilted by 70 degrees.

"If confirmed, this might be the first planet of this type" -Guillame Hébrard.

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Title: A dynamical perspective on additional planets in 55 Cancri
Authors: Sean N. Raymond, Rory Barnes, Noel Gorelick

Five planets are known to orbit the star 55 Cancri. The recently-discovered planet f at 0.78 AU (Fischer et al. 2008) is located at the inner edge of a previously-identified stable zone that separates the three close-in planets from planet d at 5.9 AU. Here we map the stability of the orbital space between planets f and d using a suite of n-body integrations that include an additional, yet-to-be-discovered planet g with a radial velocity amplitude of 5 m/s (planet mass = 0.5-1.2 Saturn masses). We find a large stable zone extending from 0.9 to 3.8 AU at eccentricities below 0.4. For each system we quantify the probability of detecting planets b-f on their current orbits given perturbations from hypothetical planet g, in order to further constrain the mass and orbit of an additional planet. We find that large perturbations are associated with specific mean motion resonances (MMRs) with planets f and d. We show that two MMRs, 3f:1g (the 1:3 MMR between planets g and f) and 4g:1d cannot contain a planet g. The 2f:1g MMR is unlikely to contain a planet more massive than about 20 Earth masses. The 3g:1d and 5g:2d MMRs could contain a resonant planet but the resonant location is strongly confined. The 3f:2g, 2g:1d and 3g:2d MMRs exert a stabilising influence and could contain a resonant planet. Furthermore, we show that the stable zone may in fact contain 2-3 additional planets, if they are ~50 Earth masses each. Finally, we show that any planets exterior to planet d must reside beyond 10 AU.

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Title: A Spitzer Study of Debris Disks In The Young Nearby Cluster NGC 2232: Icy Planets Are Common Around ~ 1.5--3 Solar-Mass Stars
Authors: Thayne Currie (CfA), Peter Plavchan (IPAC/Caltech), Scott J. Kenyon (CfA)

We describe Spitzer IRAC and MIPS observations of the nearby 25 Myr-old open cluster NGC 2232. Combining these data with ROSAT All-Sky Survey observations, proper motions, and optical photometry/spectroscopy, we construct a list of highly probable cluster members. We identify 1 A-type star, HD 45435, with definite excess emission at 4.5--24 micron indicative of debris from terrestrial planet formation. We also identify 2--4 late-type stars with possible 8 micron excesses, and 8 early-type stars with definite 24 micron excesses. Constraints on the dust luminosity and temperature suggest that the detected excesses are produced by debris disks. From our sample of B and A stars, stellar rotation appears correlated with 24 micron excess, a result expected if massive primordial disks evolve into massive debris disks. To explore the evolution of the frequency and magnitude of debris around A-type stars, we combine our results with data for other young clusters. The frequency of debris disks around A-type stars appears to increase from ~ 25% at 5 Myr to ~ 50--60% at 20--25 Myr. Older A-type stars have smaller debris disk frequencies: ~ 20% at 50--100 Myr. For these ages, the typical level of debris emission rises from 5--20 Myr and then declines. Because 24 micron dust emission probes icy planet formation around A-type stars, our results suggest that the frequency of icy planet formation is eta(i) > 0.5--0.6. Thus, most A-type stars (approx. 1.5--3 Msun) produce icy planets.

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Title: Planetary Companions to Evolved Intermediate-Mass Stars: 14 Andromedae, 81 Ceti, 6 Lyncis, and HD 167042
Authors: Bun'ei Sato, Eri Toyota, Masashi Omiya, Hideyuki Izumiura, Eiji Kambe, Seiji Masuda, Yoichi Takeda, Yoichi Itoh, Hiroyasu Ando, Michitoshi Yoshida, Eiichiro Kokubo, Shigeru Ida

We report on the detection of four extrasolar planets orbiting evolved intermediate-mass stars from a precise Doppler survey of G and K giants at Okayama Astrophysical Observatory. All of the host stars are considered to be formerly early F-type or A-type dwarfs when they were on the main sequence. 14 And (K0 III) is a clump giant with a mass of 2.2 M_solar and has a planet of minimum mass m_2sin i=4.8 M_Jup in a nearly circular orbit with a 186 day period. This is one of the innermost planets around evolved intermediate-mass stars and such planets have only been discovered in clump giants. 81 Cet (G5 III) is a clump giant with 2.4 M_solar hosting a planet of m_2sin i=5.3 M_Jup in a 953 day orbit with an eccentricity of e=0.21. 6 Lyn (K0 IV) is a less evolved subgiant with 1.7 M_solar and has a planet of m_2sin i=2.4 M_Jup in a 899 day orbit with e=0.13. HD 167042 (K1 IV) is also a less evolved star with 1.5 M_solar hosting a planet of m_2sin i=1.6 M_Jup in a 418 day orbit with e=0.10. This planet was independently announced by Johnson et al. (2008, ApJ, 675, 784). All of the host stars have solar or sub-solar metallicity, which supports the lack of metal-rich tendency in planet-harbouring giants in contrast to the case of dwarfs.

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