Giant Planet Formation by Gravitational Instability

“Gravitational instability where particularly massive disks (it is unclear how common massive disks are) can become unstable and collapse into gas giants (bypassing the need to rst form a planetary core) is a competing scenario (Cameron 1978 [19], Boss 1997 [14]).”

“Such clumps can contract to form giant gaseous protoplanets (Boss 1997, 1998). The basic idea of this model was proposed earlier by Kuiper (1951), Urey (1966) and Cameron (1978) by considering the formation of giant planets in the solar nebula. This idea believes in the existence of a set of identical protoplanets, id…”

“…most formation models of planets or low-mass brown dwarf companions - core accretion (e.g., Pollack et al. 1996), gravitational instability (e.g., Boss 1997), and fragmentation of a pre-stellar core (e.g., Padoan & Nordlund 2002; Bate et al. 2003) - cannot easily explain the existence of…”

“A second model for giant planet formation is ‘gravitational (disk) instability’ in which gas giant planets form as a result of gravitational fragmentation in the disk surrounding the young star (Boss 1997; Durisen et al. 2007).”

“…2009): accretion of planetesimals into a core, followed by gas accretion (e.g., Pollack et al. 1996; Kenyon & Bromley 2009; Brauer et al. 2008), and instabilities in the protoplanetary disk (PPD) that causes fragmentation (e.g., Cameron 1978; Mayer et al. 2002; Boss 1997, 2006; Brauer et al. 2008).”

“The surface densities of the initial disk models are too low by several orders of magnitude for the disk instability model of Boss (1997) to apply.”

“her disks, gravitational instability leads to fragmentation and the formation of bound objects. This may cause the truncation of circumnuclear disks (Goodman, 2003), or the formation of planets (e.g. Boss 1997, and references therein). We will restrict attention to disks whose potential is dominated by the central obj…”

“Boss (1997, 1998) was the first to revive the idea that such clumps could become permanently bound and evolve into gas giant planets.”

“One such theory follows the idea that planets formed the same way as stars, by gravitational collapse, where most of the gas and dust in a region of the protoplanetary disk collapses to form a planet (Boss, 1997).”

“, 1996) and gravitational instability (Boss, 1997), describe planets forming in mostly circular, well-aligned circumstellar disks, it is important to explain why the mean eccentricity of discovered exoplanets is currently 0.191, with many of the highest eccentricities found in single-planet systems (78% with e > 0.5 a…”

“This leads to direct fragmentation of the gas into massive planets (Boss 1997).”