Asteroid flux towards circumprimary habitable zones in binary star systems

Abstract

Context. So far, more than 130 extrasolar planets have been found in multiple stellar systems. Dynamical simulations show that the outcome of the planetary formation process can lead to different planetary architecture (i.e. location, size, mass, and water content) when the star system is single or double. Aims. 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 (HZ). In this study, we make a comparison of several binary star systems and how efficient they are at moving icy asteroids from beyond the snow line into orbits crossing the HZ. Methods. We modelled a belt of 10 000 asteroids (remnants from the late phase of the 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 integrated separately. In this statistical study, several double star configurations with a G-type star as primary are investigated. Results. 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 in 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 not only favours a faster depletion of our disk of planetesimals, but can also bring 4-5 times more water into the whole HZ.

The Influence of Orbital Resonances on the Water Transport to Objects in the Circumprimary Habitable Zone of Binary Star Systems

“…For each binary configuration studied, the main source of impactors is located in the region R 2 . As already proved by Bancelin et al (2016), this region is the primary source of icy asteroids reaching the HZ for this configuration, as both orbital resonances overlap in the asteroid belt. Contrary to the previous case (SR ∈ HZ), the water distribution in the HZ follows the r A distribution and EPs located around 1.0 au, on circular motion, can interact with fewer icy asteroids than EPs located at larger semi major axes.…”

“…We can also notice that the number of crossings is higher when the SR is located inside the belt (right panels). This was also pointed out by Bancelin et al (2016) and can be explained by possible overlaps of the SR with MMRs.…”

“…These water-rich bodies are either planetary embryos (Haghighipour and Raymond 2007) or asteroids as shown for our Earth in Morbidelli et al (2000) and O'Brien et al (2014). More recently, Bancelin et al (2015) gave a statistical estimate of the contribution of asteroids in bearing water material onto the circumprimary HZ of binary star systems. They showed that the differences in the statistical results strongly depend on the initial configuration of the binary star systems hosting a gas giant.…”

“…They showed that the differences in the statistical results strongly depend on the initial configuration of the binary star systems hosting a gas giant. Bancelin et al (2016) showed that in such configurations an SR can be located within the planetesimal belt where an overlap with MMRs may lead to strong perturbations causing a flux of asteroids moving towards the HZ. In the case of icy asteroids, they will contribute to the water transport onto a planet moving in the HZ.…”

Dynamics and habitability in circumstellar planetary systems of known binary stars

“…Indeed, Bancelin et al (2015Bancelin et al ( , 2016 showed that SR can exist inside the main-belt analogues of certain binary stargiant planet configurations. When the SR lies in the asteroid belt it can overlap with MMRs and be responsible for a high rate of asteroids crossing the HZ and, therefore, for an enhanced impact rate and water transport to the HZ (Bancelin, in preparation).…”