On the ejection of Earth-mass planets from the habitable zones of the solar twins HD 20782 and HD 188015

Abstract

We provide a detailed statistical study of the ejection of fictitious Earth-mass planets from the habitable zones of the solar twins HD 20782 and HD 188015. These systems possess a giant planet that crosses into the stellar habitable zone, thus effectively thwarting the possibility of habitable terrestrial planets. In the case of HD 188015, the orbit of the giant planet is essentially circular, whereas in the case of HD 20782, it is extremely elliptical. As starting positions for the giant planets, we consider both the apogee and perigee positions, whereas the starting positions of the Earth-mass planets are widely varied. For the giant planets, we consider models based on their minimum masses as well as models where the masses are increased by 30 %. Our simulations indicate a large range of statistical properties concerning the ejection of the Earth-mass planets from the stellar habitable zones. For example, it is found that the ejection times for the Earth-mass planets from the habitable zones of HD 20782 and HD 188015, originally placed at the centre of the habitable zones, vary by a factor of y200 and y1500, respectively, depending on the starting positions of the giant and terrestrial planets. If the mass of the giant planet is increased by 30 %, the variation in ejection time for HD 188015 increases to a factor of y6000. However, the short survival times of any Earth-mass planets in these systems are of no surprise. It is noteworthy, however, that considerable differences in the survival times of the Earth-mass planets are found, which may be relevant for establishing guidelines of stability for systems with less intrusive giant planets.

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

“…The existence of HD 23079 b, a planet even more massive than Jupiter, makes it difficult for a terrestrial planet to orbit HD 23079 at a similar distance without being heavily affected by the giant planet; see the results from previous case studies by Noble et al (2002) and Yeager et al (2011) who focused on the dynamics of HD 20782, HD 188015 and HD 210277. The existence of HD 23079 b, a planet even more massive than Jupiter, makes it difficult for a terrestrial planet to orbit HD 23079 at a similar distance without being heavily affected by the giant planet; see the results from previous case studies by Noble et al (2002) and Yeager et al (2011) who focused on the dynamics of HD 20782, HD 188015 and HD 210277.…”

The stability of the suggested planet in the ν Octantis system: a numerical and statistical study

“…Thus, it is unclear if or how the time‐scale of orbital stability will change due to other positional choices in the view of previous studies, which have demonstrated a significant sensitivity in the outcome of stability simulations on the adopted planetary starting angle (e.g. Fatuzzo et al 2006; Yeager, Eberle & Cuntz 2011). Thirdly, and foremost, Eberle & Cuntz did not utilize detailed stability criteria for the identification of the onset of orbital instability.…”

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

“…The existence of HD 23079b, a planet about two and a half times more massive than Jupiter, makes it difficult for a terrestrial planet to orbit HD 23079 at a similar distance without being heavily affected by the giant planet; see results from previous case studies by Noble et al (2002) and Yeager, Eberle, & Cuntz (2011), who focused on the dynamics of HD Dvorak et al (2004) and Eberle et al (2011).…”

“…The orbital parameters of HD 23079b are relatively similar to those of Mars, implying that HD 23079b is orbiting its host star in or near the outskirts of the stellar HZ; see discussion below. The existence of HD 23079b, a planet about two and a half times more massive than Jupiter, makes it difficult for a terrestrial planet to orbit HD 23079 at a similar distance without being heavily affected by the giant planet; see results from previous case studies by Noble et al (2002) and Yeager et al (2011) who focused on the dynamics of HD 20782, HD 188015, and HD 210277, which are systems of similar dynamical settings. Concerning HD 23079, previous investigations pertaining to habitable terrestrial Trojan planets were given by Dvorak et al (2004) and Eberle et al (2011).…”