FORETELLINGS OF RAGNARÖK: WORLD-ENGULFING ASYMPTOTIC GIANTS AND THE INHERITANCE OF WHITE DWARFS
By A. Mustill, Eva Villaver. 2012
143 citations recorded by the source corpus.
The search for planets around white dwarf stars, and evidence for dynamical instability around them in the form of atmospheric pollution and circumstellar disks, raises questions about the nature of planetary systems that can survive the vicissitudes of the asymptotic giant branch (AGB). We study the competing effects, on planets at several AU from the star, of strong tidal forces arising from the star's large convective envelope, and of the planets' orbital expansion due to stellar mass loss. We study, for the first time, the evolution of planets while following each thermal pulse on the AGB. For Jovian planets, tidal forces are strong, and can pull into the envelope planets initially at ∼3 AU for a 1 M☉ star and ∼5 AU for a 5 M☉ star. Lower-mass planets feel weaker tidal forces, and terrestrial planets initially within 1.5–3 AU enter the stellar envelope. Thus, low-mass planets that begin inside the maximum stellar radius can survive, as their orbits expand due to mass loss. The inclusion of a moderate planetary eccentricity slightly strengthens the tidal forces experienced by Jovian planets. Eccentric terrestrial planets are more at risk, since their eccentricity does not decay and their small pericenter takes them inside the stellar envelope. We also find the closest radii at which planets will be found around white dwarfs, assuming that any planet entering the stellar envelope is destroyed. Planets are in that case unlikely to be found inside ∼1.5 AU of a white dwarf with a 1 M☉ progenitor and ∼10 AU of a white dwarf with a 5 M☉ progenitor.
Subfields: Astronomy and Astrophysics
View Paper: https://www.semanticscholar.org/paper/b21934baf0ea2c6023b596b69334e7223b148eea
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In Astronomy and Astrophysics
Citations in the corpus
- Dawes Review 6: The Impact of Companions on Stellar Evolution (2016, background): “…into the star when the star is extended, the planet needs to be at initial orbital separation between two and four times the radius the star has during its giant phases (depending on the strength of tides; e.g., Villaver & Livio 2009, Mustill & Villaver 2012, Madappatt, De Marco, & Villaver 2016).”
- The frequency of planetary debris around young white dwarfs (2014, background): “…focusing on the future of the solar system (Sackmann et al. 1993; Duncan & Lissauer 1998), a number of theoretical studies have shown that a fraction of planets can survive the red- giant stage of their host stars (Villaver & Livio 2007, 2009; Nordhaus et al. 2010; Mustill & Villaver 2012).”
- Simulations of two-planet systems through all phases of stellar evolution: implications for the instability boundary and white dwarf pollution (2013, background): “Mustill & Villaver (2012) model individual thermal pulses and demonstrate how they affect planetary stability.”
- Formation of planetary debris discs around white dwarfs – I. Tidal disruption of an extremely eccentric asteroid (2014, background): “At a minimum, the asteroids need to reside beyond about a couple of au to avoid engulfment into their star’s giant branch envelope (Mustill & Villaver 2012).”