[Baps] Naoz seminar on "The Origin of Retrograde Hot Jupiters", Monday 24th

[Paul Withers]

-------- Original Message --------
Subject: [Announce] Astrophysics Seminar 10/24/2011
Date: Fri, 21 Oct 2011 11:07:36 -0400
From: Forbez, Xiomara M <xio at bu.edu>
To: announce at skynet.bu.edu <announce at skynet.bu.edu>, 
mgurwell at cfa.harvard.edu <mgurwell at cfa.harvard.edu>, 
amoullet at cfa.harvard.edu <amoullet at cfa.harvard.edu>

Astrophysics Seminar
Monday, October 24, 2011
Refreshments at 3:45pm in CAS 500
Talk begins at 4:00pm in CAS 502

Dr. Smadar Naoz
Harvard-Smithsonian Center for Astrophysics

The Origin of Retrograde Hot Jupiters

The search for extra-solar planets has led to the surprising discovery
of many Jupiter-like planets in very close proximity to their host
star, the so-called ``hot Jupiters'' (HJ). Even more surprisingly,
many of these HJs have orbits that are eccentric or highly inclined
with respect to the equator of the star, and some (about 25%) even
orbiting counter to the spin direction of the star. This poses a
unique challenge to all planet formation models. We show that secular
interactions between Jupiter-like planet and another perturber in the
system can easily produce retrograde HJ orbits. We show that in the
frame of work of secular hierarchical triple system (the so-called
Kozai mechanism) the inner orbit's angular momentum component parallel
to the total angular momentum (i.e., the z-component of the inner
orbit angular momentum) need not be constant. In fact, it can even
change sign, leading to a retrograde orbit. A brief excursion to very
high eccentricity during the chaotic evolution of the inner orbit
allows planet- star tidal interactions to rapidly circularize that
orbit, decoupling the planets and forming a retrograde hot Jupiter. We
estimate the relative frequencies of retrograde orbits and counter to
the stellar spin orbits using Monte Carlo simulations, and find that
the they are consistent with the observations. The high observed
incidence of planets orbiting counter to the stellar spin direction
may suggest that planet- -planet secular interactions are an important
part of their dynamical history.


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Xiomara Forbez
Fiscal Administrator
Institute for Astrophysical Research
Boston University
(617)358-0603
xio at bu.edu