275 research outputs found
Analytic orbit propagation for transiting circumbinary planets
The herein presented analytical framework fully describes the motion of
coplanar systems consisting of a stellar binary and a planet orbiting both
stars on orbital as well as secular timescales. Perturbations of the Runge-Lenz
vector are used to derive short period evolution of the system, while octupole
secular theory is applied to describe its long term behaviour. A post Newtonian
correction on the stellar orbit is included. The planetary orbit is initially
circular and the theory developed here assumes that the planetary eccentricity
remains relatively small (e_2<0.2). Our model is tested against results from
numerical integrations of the full equations of motion and is then applied to
investigate the dynamical history of some of the circumbinary planetary systems
discovered by NASA's Kepler satellite. Our results suggest that the formation
history of the systems Kepler-34 and Kepler-413 has most likely been different
from the one of Kepler-16, Kepler-35, Kepler-38 and Kepler-64, since the
observed planetary eccentricities for those systems are not compatible with the
assumption of initially circular orbits.Comment: Accepted for publication in Ap
Effects of variable eccentricity on the climate of an Earth-like world
The Kepler era of exoplanetary discovery has presented the Astronomical
community with a cornucopia of planetary systems very different from the one
which we inhabit. It has long been known that Jupiter plays a major role in the
orbital parameters of Mars and it's climate, but there is also a long-standing
belief that Jupiter would play a similar role for Earth if not for its large
moon. Using a three dimensional general circulation model (3-D GCM) with a
fully-coupled ocean we simulate what would happen to the climate of an
Earth-like world if Mars did not exist, but a Jupiter-like planet was much
closer to Earth's orbit. We investigate two scenarios that involve evolution of
the Earth-like planet's orbital eccentricity from 0--0.283 over 6500 years, and
from 0--0.066 on a time scale of 4500 years. In both cases we discover that
they would maintain relatively temperate climates over the time-scales
simulated. More Earth-like planets in multi-planet systems will be discovered
as we continue to survey the skies and the results herein show that the
proximity of large gas giant planets may play an important role in the
habitability of these worlds. These are the first such 3-D GCM simulations
using a fully-coupled ocean with a planetary orbit that evolves over time due
to the presence of a giant planet.Comment: 11 pages, 4 figures, 1 table, submitted to ApJ Letters. Updated
figures and discussion at referee reques
Improved equations for eccentricity generation in hierarchical triple systems
In a series of papers, we developed a technique for estimating the inner
eccentricity in hierarchical triple systems, with the inner orbit being
initially circular. However, for certain combinations of the masses and the
orbital elements, the secular part of the solution failed. In the present
paper, we derive a new solution for the secular part of the inner eccentricity,
which corrects the previous weakness. The derivation applies to hierarchical
triple systems with coplanar and initially circular orbits. The new formula is
tested numerically by integrating the full equations of motion for systems with
mass ratios from 10^(-3) to 10^(3). We also present more numerical results for
short term eccentricity evolution, in order to get a better picture of the
behaviour of the inner eccentricity.Comment: Accepted for publication in MNRA
Long term evolution of planetary systems with a terrestrial planet and a giant planet
We study the long term orbital evolution of a terrestrial planet under the
gravitational perturbations of a giant planet. In particular, we are interested
in situations where the two planets are in the same plane and are relatively
close. We examine both possible configurations: the giant planet orbit being
either outside or inside the orbit of the smaller planet. The perturbing
potential is expanded to high orders and an analytical solution of the
terrestrial planetary orbit is derived. The analytical estimates are then
compared against results from the numerical integration of the full equations
of motion and we find that the analytical solution works reasonably well. An
interesting finding is that the new analytical estimates improve greatly the
predictions for the timescales of the orbital evolution of the terrestrial
planet compared to an octupole order expansion. Finally, we briefly discuss
possible applications of the analytical estimates in astrophysical problems.Comment: Accepted for publication in MNRA
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