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

Abstract

The aim of our study is to investigate the possibility of habitable moons orbiting the giant planet HD 23079b, a Jupitermass planet, which follows a low-eccentricity orbit in the outer region of HD 23079's habitable zone. We show that HD 23079b is able to host habitable moons in prograde and retrograde orbits, as expected, noting that the outer stability limit for retrograde orbits is increased by nearly 90% compared with that of prograde orbits, a result consistent with previous generalised studies. For the targeted parameter space, it was found that the outer stability limit for habitable moons varies between 0.05236 and 0.06955 AU (prograde orbits) and between 0.1023 and 0.1190 AU (retrograde orbits), depending on the orbital parameters of the Jupiter-type planet if a minimum mass is assumed. These intervals correspond to 0.306 and 0.345 (prograde orbits) and 0.583 and 0.611 (retrograde orbits) of the planet's Hill radius. Larger stability limits are obtained if an increased value for the planetary mass m p is considered; they are consistent with the theoretically deduced relationship of m 1/3 p . Finally, we compare our results with the statistical formulae of Domingos, Winter, & Yokoyama, indicating both concurrence and limitations.

Origin and Stability of Exomoon Atmospheres: Implications for Habitability

“…Although convincing observational evidence of the existence of exomoons is still missing (e.g., Kipping et al 2012 ), as mentioned before, many studies are not only focusing on exomoon detectability, but also on various habitability aspects concerning these potentially exciting objects. This comprises topics like tidal heating and energy sources (e.g., Reynolds et al 1987 ; Scharf 2006 ; Cassidy et al 2009 ; Heller 2012 ; Heller and Barnes 2013 , 2014b ), orbital stability (e.g., Barnes and O’Brien 2002 ; Donnison 2010a , b , 2014 ; Weidner and Horne 2010 ; Cuntz et al 2013 ; Forgan and Kipping 2013 ; Gong et al 2013 ), illumination effects (Heller and Barnes 2013 ; Forgan and Yotov 2014 ), Hill stability (e.g., Heller and Barnes 2014b ; Donnison 2010a , b ; Hinkel and Kane 2013 ), magnetic environment (Heller and Zuluaga 2013 ), formation scenarios (e.g., Kipping et al 2012 ; Heller and Pudritz 2014 ), and biosignatures (Kiang et al 2007 ; Grenfell et al 2010 ; Kaltenegger 2010 ; Kaltenegger et al 2013 ; Rugheimer et al 2013 ). …”

“…orbital stability (e.g., Barnes and O’Brien 2002 ; Donnison 2010a , b , 2014 ; Weidner and Horne 2010 ; Cuntz et al 2013 ; Forgan and Kipping 2013 ; Gong et al 2013 ),…”

“…An important requirement that a regular or irregular exomoon may evolve to a habitat is its long-time orbital stability (e.g., Weidner and Horne 2010 ; Cuntz et al 2013 ; Forgan and Kipping 2011 ; Donnison 2014 ; Gong et al 2013 ). Barnes and O’Brien ( 2002 ) showed that hypothetical exomoons with 1 M ⊕ around Jupiter-mass gas giants are dynamically stable for the lifetime of the Solar System in star systems where the stellar mass is greater than >0.15 M ⊙ .…”

“…For instance, Cuntz et al ( 2013 ) investigated the possibility of stable orbits for habitable exomoons around the Jupiter-mass gas giant HD 23079b, which has a low-eccentricity orbit in the outer region of HD 23079’s HZ. These authors found that for the minimum mass case of an exomoon, the orbital stability limits of the Jupiter-mass gas giant HD 23079b could vary between 0.05236 and 0.06955 AU for prograde orbits and between 0.1023 and 0.1190 AU for retrograde orbits, corresponding to 0.306 and 0.345 (prograde orbits) and 0.583 and 0.611 (retrograde orbits) of the exoplanet’s Hill radius.…”

The three-body problem

“…The formation of such a system may experience considerable difficulties [Canup and Ward, 2006], but the capture of a terrestrial planet still remains possible [Kipping, 2009, 2013b. Other studies have used a parameter survey approach to determine the stability of possible exomoons; see applications to the system HD 23079 system [Cuntz et al, 2013]. Studies of such systems are based on the formulation of the restricted three-body problem.…”