123 research outputs found
Impact flux of asteroids and water transport to the habitable zone in binary star systems
By now, observations of exoplanets have found more than 50 binary star
systems hosting 71 planets. We expect these numbers to increase as more than
70% of the main sequence stars in the solar neighborhood are members of binary
or multiple systems. The planetary motion in such systems depends strongly on
both the parameters of the stellar system (stellar separation and eccentricity)
and the architecture of the planetary system (number of planets and their
orbital behaviour). In case a terrestrial planet moves in the so-called
habitable zone (HZ) of its host star, the habitability of this planet depends
on many parameters. A crucial factor is certainly the amount of water. We
investigate in this work the transport of water from beyond the snow-line to
the HZ in a binary star system and compare it to a single star system
Disc-protoplanet interaction Influence of circumprimary radiative discs on self-gravitating protoplanetary bodies in binary star systems
Context. More than 60 planets have been discovered so far in systems that
harbour two stars, some of which have binary semi-major axes as small as 20 au.
It is well known that the formation of planets in such systems is strongly
influenced by the stellar components, since the protoplanetary disc and the
particles within are exposed to the gravitational influence of the binary.
However, the question on how self-gravitating protoplanetary bodies affect the
evolution of a radiative, circumprimary disc is still open. Aims. We present
our 2D hydrodynamical GPU-CPU code and study the interaction of several
thousands of self-gravitating particles with a viscous and radiative
circumprimary disc within a binary star system. To our knowledge this program
is the only one at the moment that is capable to handle this many particles and
to calculate their influence on each other and on the disc. Methods. We
performed hydrodynamical simulations of a circumstellar disc assuming the
binary system to be coplanar. Our gridbased staggered mesh code relies on ideas
from ZEUS-2D, where we implemented the FARGO algorithm and an additional energy
equation for the radiative cooling according to opacity tables. To treat
particle motion we used a parallelised version of the precise Bulirsch - Stoer
algorithm. Four models in total where computed taking into account (i) only
N-body interaction, (ii) N-body and disc interaction, (iii) the influence of
computational parameters (especially smoothing) on N-body interaction, and (iv)
the influence of a quiet low-eccentricity disc while running model (ii). The
impact velocities where measured at two different time intervals and were
compared. Results. We show that the combination of disc- and N-body
self-gravity can have a significant influence on the orbit evolution of roughly
Moon sized protoplanets
Prediction of transits of solar system objects in Kepler/K2 images: An extension of the Virtual Observatory service SkyBoT
All the fields of the extended space mission Kepler/K2 are located within the
ecliptic. Many solar system objects thus cross the K2 stellar masks on a
regular basis. We aim at providing to the entire community a simple tool to
search and identify solar system objects serendipitously observed by Kepler.
The SkyBoT service hosted at IMCCE provides a Virtual Observatory (VO)
compliant cone-search that lists all solar system objects present within a
field of view at a given epoch. To generate such a list in a timely manner,
ephemerides are pre-computed, updated weekly, and stored in a relational
database to ensure a fast access. The SkyBoT Web service can now be used with
Kepler. Solar system objects within a small (few arcminutes) field of view are
identified and listed in less than 10 sec. Generating object data for the
entire K2 field of view (14{\deg}) takes about a minute. This extension of the
SkyBot service opens new possibilities with respect to mining K2 data for solar
system science, as well as removing solar system objects from stellar
photometric time-series
The shape evolution of cometary nuclei via anisotropic mass loss
Context. Breathtaking imagery recorded during the European Space Agency's
Rosetta mission confirmed the bilobate nature of comet
67P/Churyumov-Gerasimenko's nucleus. Its peculiar appearance is not unique
among comets. The majority of cometary cores imaged at high resolution exhibit
a similar build. Various theories have been brought forward as to how cometary
nuclei attain such peculiar shapes.
Aims. We illustrate that anisotropic mass loss and local collapse of
subsurface structures caused by non-uniform exposure of the nucleus to solar
irradiation can transform initially spherical comet cores into bilobed ones.
Methods. A mathematical framework to describe the changes in morphology
resulting from non-uniform insolation during a nucleus' spin-orbit evolution is
derived. The resulting partial differential equations that govern the change in
the shape of a nucleus subject to mass loss and consequent collapse of depleted
subsurface structures are solved analytically for simple insolation
configurations and numerically for more realistic scenarios.
Results. The here proposed mechanism is capable of explaining why a large
fraction of periodic comets appear to have peanut-shaped cores and why
light-curve amplitudes of comet nuclei are on average larger than those of
typical main belt asteroids of the same size.Comment: 4 pages of the main text, 2 pages of appendix, 4 figure
High order three part split symplectic integrators: Efficient techniques for the long time simulation of the disordered discrete nonlinear Schroedinger equation
While symplectic integration methods based on operator splitting are well
established in many branches of science, high order methods for Hamiltonian
systems that split in more than two parts have not been studied in great
detail. Here, we present several high order symplectic integrators for
Hamiltonian systems that can be split in exactly three integrable parts. We
apply these techniques, as a practical case, for the integration of the
disordered, discrete nonlinear Schroedinger equation (DDNLS) and compare their
efficiencies. Three part split algorithms provide effective means to
numerically study the asymptotic behavior of wave packet spreading in the DDNLS
- a hotly debated subject in current scientific literature.Comment: 5 Figures, Physics Letters A (accepted
Colliding Winds in Low-Mass Binary Star Systems: wind interactions and implications for habitable planets
Context. In binary star systems, the winds from the two components impact
each other, leading to strong shocks and regions of enhanced density and
temperature. Potentially habitable circumbinary planets must continually be
exposed to these interactions regions.
Aims. We study, for the first time, the interactions between winds from
low-mass stars in a binary system, to show the wind conditions seen by
potentially habitable circumbinary planets.
Methods. We use the advanced 3D numerical hydrodynamic code Nurgush to model
the wind interactions of two identical winds from two solar mass stars with
circular orbits and a binary separation of 0.5 AU. As input into this model, we
use a 1D hydrodynamic simulation of the solar wind, run using the Versatile
Advection Code. We derive the locations of stable and habitable orbits in this
system to explore what wind conditions potentially habitable planets will be
exposed to during their orbits.
Results. Our wind interaction simulations result in the formation of two
strong shock waves separated by a region of enhanced density and temperature.
The wind-wind interaction region has a spiral shape due to Coriolis forces
generated by the orbital motions of the two stars. The stable and habitable
zone in this system extends from approximately 1.4 AU to 2.4 AU. (TRUNCATED)Comment: 15 pages, 11 figures, to be published in A&
Asteroid flux towards circumprimary habitable zones in binary star systems: I. Statistical Overview
So far, multiple stellar systems harbor more than 130 extra solar planets.
Dynamical simulations show that the outcome of planetary formation process can
lead to various planetary architecture (i.e. location, size, mass and water
content) when the star system is single or double. In the late phase of
planetary formation, when embryo-sized objects dominate the inner region of the
system, asteroids are also present and can provide additional material for
objects inside the habitable zone (hereafter HZ). In this study, we make a
comparison of several binary star systems and their efficiency to move icy
asteroids from beyond the snow-line into orbits crossing the HZ. We modeled a
belt of 10000 asteroids (remnants from the late phase of planetary formation
process) beyond the snow-line. The planetesimals are placed randomly around the
primary star and move under the gravitational influence of the two stars and a
gas giant. As the planetesimals do not interact with each other, we divided the
belt into 100 subrings which were separately integrated. In this statistical
study, several double star configurations with a G-type star as primary are
investigated. Our results show that small bodies also participate in bearing a
non-negligible amount of water to the HZ. The proximity of a companion moving
on an eccentric orbit increases the flux of asteroids to the HZ, which could
result into a more efficient water transport on a short timescale, causing a
heavy bombardment. In contrast to asteroids moving under the gravitational
perturbations of one G-type star and a gas giant, we show that the presence of
a companion star can not only favor a faster depletion of our disk of
planetesimals but can also bring 4 -- 5 times more water into the whole HZ.Comment: Accepted for publication in A&
NEOTÏIST: A relatively Inexpensive Kinetic Impactor Demonstration Mission Concept
Mission concept: NEOTÏIST stands for Near-Earth Object Transfer of angular momentum (ÏâI) Spin Test, and is a concept for a kinetic impactor demonstration mission, which aims to change the spin rate of an asteroid by impacting it off-center (Drube et al. 2016, Engel et al. 2016). The change would be measured by means of lightcurve measurements with Earth-based telescopes. In contrast to most other kinetic impactor demonstration mission concepts, NEOTÏIST does not require a reconnaissance spacecraft to rendezvous with the target asteroid for orbit change and impact-effect measurements, and is therefore a relatively inexpensive alternative.
The NEOTÏIST mission would determine the efficiency of momentum transfer (the ÎČ-factor) during an impact, and help mature the technology required for a kinetic impactor mission, both of which are important precursor measures for a future space mission to deflect an asteroid by collisional means in an emergency impact hazard situation
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