137 research outputs found
Emerging Trends in a Period-Radius Distribution of Close-in Planets
We analyze the distribution of extrasolar planets (both confirmed and Kepler
candidates) according to their orbital periods P and planetary radii R. Among
confirmed planets, we find compelling evidence for a paucity of bodies with 3 <
R < 10 R_\oplus, where R_\oplus in the Earth's radius, and P < 2-3 days. We
have christened this region a "sub-Jovian Pampas". The same trend is detected
in multiplanet Kepler candidates. Although approximately 16 Kepler
single-planet candidates inhabit this Pampas, at least 7 are probable false
positives (FP). This last number could be significantly higher if the ratio of
FP is higher than 10%, as suggested by recent studies.
In a second part of the paper we analyze the distribution of planets in the
(P,R) plane according to stellar metallicities. We find two interesting trends:
(i) a lack of small planets (R < 4 R_\oplus) with orbital periods P < 5 days in
metal-poor stars, and (ii) a paucity of sub-Jovian planets (4 R_\oplus < R < 8
R_\oplus) with P < 100 days, also around metal-poor stars. Although all these
trends are preliminary, they appear statistically significant and deserve
further scrutiny. If confirmed, they could represent important constraints on
theories of planetary formation and dynamical evolution.Comment: Accepted in Ap
Identification and Dynamical Properties of Asteroid Families
Asteroids formed in a dynamically quiescent disk but their orbits became
gravitationally stirred enough by Jupiter to lead to high-speed collisions. As
a result, many dozen large asteroids have been disrupted by impacts over the
age of the Solar System, producing groups of fragments known as asteroid
families. Here we explain how the asteroid families are identified, review
their current inventory, and discuss how they can be used to get insights into
long-term dynamics of main belt asteroids. Electronic tables of the membership
for 122 notable families are reported on the Planetary Data System node.Comment: Asteroids IV chapte
Orbital Perturbations of the Galilean Satellites During Planetary Encounters
The Nice model of the dynamical instability and migration of the giant
planets can explain many properties of the present Solar System, and can be
used to constrain its early architecture. In the jumping-Jupiter version of the
Nice model, required from the terrestrial planet constraint and dynamical
structure of the asteroid belt, Jupiter has encounters with an ice giant. Here
we study the survival of the Galilean satellites in the jumping-Jupiter model.
This is an important concern because the ice-giant encounters, if deep enough,
could dynamically perturb the orbits of the Galilean satellites, and lead to
implausible results. We performed numerical integrations where we tracked the
effect of planetary encounters on the Galilean moons. We considered three
instability cases from Nesvorny & Morbidelli (2012) that differed in the number
and distribution of encounters. We found that in one case, where the number of
close encounters was relatively small, the Galilean satellite orbits were not
significantly affected. In the other two, the orbital eccentricities of all
moons were excited by encounters, Callisto's semimajor axis changed, and, in a
large fraction of trials, the Laplace resonance of the inner three moons was
disrupted. The subsequent evolution by tides damps eccentricities and can
recapture the moons in the Laplace resonance. A more important constraint is
represented by the orbital inclinations of the moons, which can be excited
during the encounters and not appreciably damped by tides. We find that one
instability case taken from Nesvorny & Morbidelli (2012) clearly fails this
constraint. This shows how the regular satellites of Jupiter can be used to set
limits on the properties of encounters in the jumping-Jupiter model, and help
us to better understand how the early Solar System evolved.Comment: The Astronomical Journal, in pres
Origin of the peculiar eccentricity distribution of the inner cold Kuiper belt
Dawson and Murray-Clay (2012) pointed out that the inner part of the cold
population in the Kuiper belt (that with semi major axis a<43.5 AU) has orbital
eccentricities significantly smaller than the limit imposed by stability
constraints. Here, we confirm their result by looking at the orbital
distribution and stability properties in proper element space. We show that the
observed distribution could have been produced by the slow sweeping of the 4/7
mean motion resonance with Neptune that accompanied the end of Neptune's
migration process. The orbital distribution of the hot Kuiper belt is not
significantly affected in this process, for the reasons discussed in the main
text. Therefore, the peculiar eccentricity distribution of the inner cold
population can not be unequivocally interpreted as evidence that the cold
population formed in-situ and was only moderately excited in eccentricity; it
can simply be the signature of Neptune's radial motion, starting from a
moderately eccentric orbit. We discuss how this agrees with a scenario of giant
planet evolution following a dynamical instability and, possibly, with the
radial transport of the cold population.Comment: in press in Icaru
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