—where the star is the oversized baby of the system, with the gas-giant planet as its older progenitor.
The discovery of gas-giant exoplanets in low hot orbits falsified the core accretion standard model of giant planet formation, but the theory was rescued by appending the ad hoc secondary mechanism of planetary migration. Failing theories often require ad hoc secondary mechanisms to prevent falsification, whereas good theories are predictive. Furthermore, good theories are fertile, unifying formerly disparate phenomena.
The alternative hypothesis presented here suggests that gas giant exoplanets were the former prestellar/protostellar cores in stellar systems that turned themselves inside out during massive disk instabilities. When a protoplanetary disk is much-more massive than its diminutive prestellar/protostellar core, the disk has inertial dominance of the system, which in practical terms means that the diminutive core is unable to damp down disk inhomogeneities from amplifying into full-fledged disk instability. A stellar-mass disk instability will inertially displace its (older) planetary-mass prestellar/protostellar core into a satellite orbit around the nascent disk instability object, where the disk instability object evolves into the host star. This alternative catastrophic planet-star formation mechanism is designated, 'flip-flop fragmentation' (FFF), where stellar systems with multiple gas-giant planets underwent multiple sequential episodes of FFF.
Thus, if gas-giant planets were the original stellar cores of their stellar systems, then the host stars are the Baby Hueys of these systems, resulting in gas-giant planets that are older than their host stars.
A counterintuitive discovery found that accretion disk mass decreases rapidly with protostellar evolution (Tychoniec et al., 2018), which contradicts the standard model understanding. Accretion disk dust mass was measured to decrease from 248 M⊕ in Class 0 protostars, to 96 M⊕ in Class I protostars, to 5-15 M⊕ in Class II protostars, where dust mass is a proxy for total disk mass. This finding indicates an early crossover point, where the disk mass greatly exceeds the prestellar/protostellar core mass, which is a requirement of FFF. (The FFF hypothesis predicted stellar mass protoplanetary disks prior to the 2018 Tychoniec study, and thus has 1 prediction by 1 study to its predictive credit.)
Gas-giant exoplanets exhibit several seemingly ad hoc phenomena that are unified by FFF:
1) A 4 Mj desert
2) Hot Jupiters in polar orbits
3) Bimodal distribution of hot and cold Jupiters
1) A 4 Mj desert:
¶ The first hydrostatic core (FHSC) phase of prestellar objects marks the temporal transition between prestellar and protostellar. In the earliest prestellar phase of gravitational collapse, the central prestellar object (the nascent star) is transparent to infrared radiation, and thus remains isothermally cold, but once the molecule number density reaches about 10^10 molecules per cubic centimeter, the prestellar object gradually becomes opaque to infrared radiation, which causes it to heat up and swell up, becoming a 'hydrostatic' object for the first time that is supported against further collapse by its thermal gas pressure. This brief FHSC phase is the puffiest phase of young stellar objects, which can have radii of ~ 5–10 AU. The pithy FHSC phase ends abruptly when the internal temperature reaches about 2000 K, causing endothermic dissociation of molecular hydrogen (H2) into atomic hydrogen (H I). This endothermic process causes a 'second collapse', bursting the FHSC bubble.
¶ The FHSC phase is a relatively brief phase, lasting only a few thousand years, but during its existence, the central prestellar object is viscously engaged with its surrounding accretion disk, which may damp down (spiral) density waves in the accretion disk from amplifying into disk instability. So FFF can neatly explain the 4 Mj desert if there is a temporal hiatus in FFF during the pithy FHSC phase of young stellar objects, where the mass of the FHSC is ~ 4 Mj. (In actuality, the FHSC core mass is poorly constrained by both theory and observation, but it is often stated to be about a Jupiter mass.)
¶ Thus, gas-giant exoplanets of < 4 Mj represent FFF of prestellar objects, and exoplanets > 4 Mj represent FFF of protostellar objects. (If the standard model has an explanation for the 4 Mj desert, I haven't come across it.)
2) Hot Jupiters in polar orbits:
Hot Jupiters exhibit bimodal obliquity, with a propensity to orbit in either high-obliquity polar orbits or low-obliquity equatorial orbits around their host stars. FFF initially results in a pithy disk instability object (nascent star) orbited by its former prestellar/protostellar core (nascent gas-giant planet) in a planetary satellite orbit. If the system barycenter, between the nascent star and nascent planet, competes for the local center of rotation with the spin of the disk instability object, then a lower energy state (more massive star) may be attained by physically torquing the rotation axis of the disk instability object perpendicular (90°) to the rotation axis of the system barycenter. This torquing process may occur in the form of a gradual precession of the disk instability object spin axis. Intuitively, one would expect the less-massive planet to torque its orbital axis perpendicular to the more-mass star, but the much-more massive disk instability object torques instead, because the planetary orbit contains much-more angular momentum than the nascent stellar rotation. (In our solar system, the planetary orbits contain more than 99% of the total angular momentum of the solar system, with the Sun's rotation comprising less than 1%, despite the Sun having 99.98% of the total mass.)
3) Bimodal distribution of hot and cold Jupiters:
Gas-giant exoplanets are bimodally distributed into 'hot Jupiters' in low hot orbits and 'cold Jupiters' in high cold orbits, with a 10–100 day orbital-period valley in between, which the standard model struggles to explain. Alternatively, some young stellar objects are found to have 'pseudo-disks' surrounding their accretion disks, such that hot Jupiters may represent FFF of accretion disks and cold Jupiters may represent FFF of more-distant pseudo-disks, with the gap between accretion disks and pseudo-disks explaining the orbital-period valley.
Our solar system and super-Earths:
Our highly unusual solar system is suggested here to have been formed by an alternative Russian nesting doll hypothesis, designated 'trifurcation', which will not be discussed here. And super-Earth were formed by a third planet formation mechanism, designated 'hybrid accretion', where planetesimals formed by streaming instability aggregate by core accretion to form super-Earth planets. In the case of stellar systems with multiple super-Earth planets, they form sequentially from the inside out, with the super-Earth closest to the star forming first.
....................
Reference:
Tychoniec, Lukasz; Tobin, John J.; Karsaka, Agata; Chandler, Claire; Dunham, Michael M.; Harris, Robert J.; Kratter, Kaitlin M.; Li, Zhi-Yun; Looney, Leslie W.; Melis Carl; Perez, Laura M.; Sadavoy, Sarah I.; Segura-Cox, Dominique; and van Dishoeck, Ewine F., (2018), THE VLA NASCENT DISK AND MULTIPLICITY SURVEY OF PERSEUS PROTOSTARS (VANDAM). IV. FREE-FREE EMISSION FROM PROTOSTARS: LINKS TO INFRARED PROPERTIES, OUTFLOW TRACERS, AND PROTOSTELLAR DISK MASSES.
The discovery of gas-giant exoplanets in low hot orbits falsified the core accretion standard model of giant planet formation, but the theory was rescued by appending the ad hoc secondary mechanism of planetary migration. Failing theories often require ad hoc secondary mechanisms to prevent falsification, whereas good theories are predictive. Furthermore, good theories are fertile, unifying formerly disparate phenomena.
The alternative hypothesis presented here suggests that gas giant exoplanets were the former prestellar/protostellar cores in stellar systems that turned themselves inside out during massive disk instabilities. When a protoplanetary disk is much-more massive than its diminutive prestellar/protostellar core, the disk has inertial dominance of the system, which in practical terms means that the diminutive core is unable to damp down disk inhomogeneities from amplifying into full-fledged disk instability. A stellar-mass disk instability will inertially displace its (older) planetary-mass prestellar/protostellar core into a satellite orbit around the nascent disk instability object, where the disk instability object evolves into the host star. This alternative catastrophic planet-star formation mechanism is designated, 'flip-flop fragmentation' (FFF), where stellar systems with multiple gas-giant planets underwent multiple sequential episodes of FFF.
Thus, if gas-giant planets were the original stellar cores of their stellar systems, then the host stars are the Baby Hueys of these systems, resulting in gas-giant planets that are older than their host stars.
A counterintuitive discovery found that accretion disk mass decreases rapidly with protostellar evolution (Tychoniec et al., 2018), which contradicts the standard model understanding. Accretion disk dust mass was measured to decrease from 248 M⊕ in Class 0 protostars, to 96 M⊕ in Class I protostars, to 5-15 M⊕ in Class II protostars, where dust mass is a proxy for total disk mass. This finding indicates an early crossover point, where the disk mass greatly exceeds the prestellar/protostellar core mass, which is a requirement of FFF. (The FFF hypothesis predicted stellar mass protoplanetary disks prior to the 2018 Tychoniec study, and thus has 1 prediction by 1 study to its predictive credit.)
Gas-giant exoplanets exhibit several seemingly ad hoc phenomena that are unified by FFF:
1) A 4 Mj desert
2) Hot Jupiters in polar orbits
3) Bimodal distribution of hot and cold Jupiters
1) A 4 Mj desert:
¶ The first hydrostatic core (FHSC) phase of prestellar objects marks the temporal transition between prestellar and protostellar. In the earliest prestellar phase of gravitational collapse, the central prestellar object (the nascent star) is transparent to infrared radiation, and thus remains isothermally cold, but once the molecule number density reaches about 10^10 molecules per cubic centimeter, the prestellar object gradually becomes opaque to infrared radiation, which causes it to heat up and swell up, becoming a 'hydrostatic' object for the first time that is supported against further collapse by its thermal gas pressure. This brief FHSC phase is the puffiest phase of young stellar objects, which can have radii of ~ 5–10 AU. The pithy FHSC phase ends abruptly when the internal temperature reaches about 2000 K, causing endothermic dissociation of molecular hydrogen (H2) into atomic hydrogen (H I). This endothermic process causes a 'second collapse', bursting the FHSC bubble.
¶ The FHSC phase is a relatively brief phase, lasting only a few thousand years, but during its existence, the central prestellar object is viscously engaged with its surrounding accretion disk, which may damp down (spiral) density waves in the accretion disk from amplifying into disk instability. So FFF can neatly explain the 4 Mj desert if there is a temporal hiatus in FFF during the pithy FHSC phase of young stellar objects, where the mass of the FHSC is ~ 4 Mj. (In actuality, the FHSC core mass is poorly constrained by both theory and observation, but it is often stated to be about a Jupiter mass.)
¶ Thus, gas-giant exoplanets of < 4 Mj represent FFF of prestellar objects, and exoplanets > 4 Mj represent FFF of protostellar objects. (If the standard model has an explanation for the 4 Mj desert, I haven't come across it.)
2) Hot Jupiters in polar orbits:
Hot Jupiters exhibit bimodal obliquity, with a propensity to orbit in either high-obliquity polar orbits or low-obliquity equatorial orbits around their host stars. FFF initially results in a pithy disk instability object (nascent star) orbited by its former prestellar/protostellar core (nascent gas-giant planet) in a planetary satellite orbit. If the system barycenter, between the nascent star and nascent planet, competes for the local center of rotation with the spin of the disk instability object, then a lower energy state (more massive star) may be attained by physically torquing the rotation axis of the disk instability object perpendicular (90°) to the rotation axis of the system barycenter. This torquing process may occur in the form of a gradual precession of the disk instability object spin axis. Intuitively, one would expect the less-massive planet to torque its orbital axis perpendicular to the more-mass star, but the much-more massive disk instability object torques instead, because the planetary orbit contains much-more angular momentum than the nascent stellar rotation. (In our solar system, the planetary orbits contain more than 99% of the total angular momentum of the solar system, with the Sun's rotation comprising less than 1%, despite the Sun having 99.98% of the total mass.)
3) Bimodal distribution of hot and cold Jupiters:
Gas-giant exoplanets are bimodally distributed into 'hot Jupiters' in low hot orbits and 'cold Jupiters' in high cold orbits, with a 10–100 day orbital-period valley in between, which the standard model struggles to explain. Alternatively, some young stellar objects are found to have 'pseudo-disks' surrounding their accretion disks, such that hot Jupiters may represent FFF of accretion disks and cold Jupiters may represent FFF of more-distant pseudo-disks, with the gap between accretion disks and pseudo-disks explaining the orbital-period valley.
Our solar system and super-Earths:
Our highly unusual solar system is suggested here to have been formed by an alternative Russian nesting doll hypothesis, designated 'trifurcation', which will not be discussed here. And super-Earth were formed by a third planet formation mechanism, designated 'hybrid accretion', where planetesimals formed by streaming instability aggregate by core accretion to form super-Earth planets. In the case of stellar systems with multiple super-Earth planets, they form sequentially from the inside out, with the super-Earth closest to the star forming first.
....................
Reference:
Tychoniec, Lukasz; Tobin, John J.; Karsaka, Agata; Chandler, Claire; Dunham, Michael M.; Harris, Robert J.; Kratter, Kaitlin M.; Li, Zhi-Yun; Looney, Leslie W.; Melis Carl; Perez, Laura M.; Sadavoy, Sarah I.; Segura-Cox, Dominique; and van Dishoeck, Ewine F., (2018), THE VLA NASCENT DISK AND MULTIPLICITY SURVEY OF PERSEUS PROTOSTARS (VANDAM). IV. FREE-FREE EMISSION FROM PROTOSTARS: LINKS TO INFRARED PROPERTIES, OUTFLOW TRACERS, AND PROTOSTELLAR DISK MASSES.
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