Case studies of habitable Trojan planets in the system of HD 23079

Abstract

We investigate the possibility of habitable Trojan planets in the HD 23079 star-planet system. This system consists of a solar-type star and a Jupiter-type planet, which orbits the star near the outer edge of the stellar habitable zone in an orbit of low eccentricity. We find that in agreement with previous studies Earth-mass habitable Trojan planets are possible in this system, although the success of staying within the zone of habitability is significantly affected by the orbital parameters of the giant planet and by the initial condition of the theoretical Earth-mass planet. In one of our simulations, the Earth-mass planet is captured by the giant planet and thus becomes a habitable moon.

On the Possibility of Habitable Moons in the System of HD 23079: Results from Orbital Stability Studies

“…Our study complements a previous investigation by our research group, given by Eberle et al (2011), that showed that the HD 23079 star–planet system is also a suitable candidate for hosting habitable Trojan planets.…”

“…These simulations were performed with the thoroughly tested GBS integration scheme. Incidentally, in our previous study aimed at habitable Trojan planets (Eberle et al 2011), we already encountered a by-chance scenario with a habitable moon in a retrograde orbit about the giant planet; it occurred due to a particular set-up of the initial conditions. In this case, the semimajor axis of the exomoon was identified as 0.051 AU, which is consistent with the stability limit attained in our present, more detailed study.…”

“…Long-term orbital stability in stellar HZs is a necessary condition for the evolution of any form of life, particularly intelligent life. Examples of previous studies on the orbital stability of hypothetical Earth-mass planets in stellar HZs include the works by Gehman, Adams, & Laughlin (1996), Noble, Musielak, & Cuntz (2002), Menou & Tabachnik (2003), Cuntz et al (2003), Asghari et al (2004), Jones, Underwood, & Sleep (2005), Jones, Sleep, & Underwood (2006), Jones & Sleep (2010), Kopparapu & Barnes (2010), and Eberle et al (2011). These studies explore the dynamics of multi-body systems noting that many extrasolar planetary systems contain more than one extrasolar giant planet (EGP), which is of pivotal importance for the orbital stability of possible Earth-mass objects in those systems.…”

“…For example, in the HD 23079 system, a Jupiter-mass planet is found to orbit the star in the HZ, therefore jeop-ardising the existence of habitable terrestrial planets. This system has previously been studied by Dvorak et al (2004), Schwarz et al (2007), and Eberle et al (2011). The study of HD 23079 is of particular interest because (1) the mass and spectral type of the center star is fairly similar to the Sun, (2) the Jupiter-mass planet is found to orbit the star in a nearly circular orbit, and (3) any exomoon of that planet, if such a moon exists, would therefore exhibit a relatively stable climate.…”

“…All these systems also provide the opportunity for hosting exomoons around Jupiter-type planets, including exomoons located in stellar HZs. Updated results for HD 23079 given by Eberle et al (2011) showed that this system is also well suited for the existence of habitable Earth-type Trojans, especially if a generalised stellar HZ is assumed, which in the Solar System corresponds to 0.84-1.67 AU from the Sun (Kasting, Whitmire, & Reynolds 1993); see Section 2.2 for details.…”