Geoscience Reference
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13.5
Late Stages
The stage for which the influence of a companion is probably best understood is
the final step of planetary accretion, leading from lunar-sized embryos to fully
formed planets. Several studies have shown that the regions where embryo accretion
can proceed roughly correspond to those for orbital stability (Barbieri et al. 2002 ;
Quintana et al. 2002 , 2007 ; Haghighipour and Raymond 2007 ; Guedes et al.
2008 ; Haghighipour et al. 2010 ). This is a further reassuring result for all known
exoplanets in binaries. As an illustration, we show in Fig. 13.6 the results obtained
by Quintana et al. ( 2002 ) for the late stages of planet formation around an ǛCen-
like binary. As can be clearly seen, even in such a tight binary, planetary objects can
grow within 2 AU region from the primary star.
More recent work on these late stages has been devoted to more specific issues.
As an illustration, we present here results obtained by Haghighipour and Raymond
( 2007 ) that focus on the level of water delivery and water mixing in the terrestrial
regions within a binary, assuming that a giant planet could form further out in the
disc. The authors considered a binary with a solar-mass primary and a Jupiter-
mass giant planet at 5 AU. The mass of the secondary star was taken to be 0.5,
Fig. 13.6 Late stages of planet formation around the primary of an Ǜ Centauri-like binary. The
initial disc consists of a mixture of 14 already formed embryos of lunar mass and 140 massive
planetesimals of mass 9:33 10 3 M ˚ (Results taken from Quintana et al. ( 2002 ), courtesy of the
Astrophysical Journal)
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