Collisional Cascades in Planetesimal Disks. II. Embedded Planets

By S. Kenyon, B. Bromley. 2003

171 citations recorded by the source corpus.

We use a multiannulus planetesimal accretion code to investigate the growth of icy planets in the outer regions of a planetesimal disk. In a quiescent minimum-mass solar nebula, icy planets grow to sizes of 1000–3000 km on a timescale tP ≈ (15–20)[a/(30 AU)]3 Myr, where a is the distance from the central star. Planets form faster in more massive nebulae. Newly formed planets stir up leftover planetesimals along their orbits and produce a collisional cascade in which icy planetesimals are slowly ground to dust. The dusty debris of planet formation has physical characteristics similar to those observed in β Pic and HR 4796A and other debris disks. The computed dust masses are Md(r ≲ 1 mm) ∼ 1026(M0/MMMSN) g and Md(1 mm ≲ r ≲ 1 m) ∼ 1027(M0/MMMSN) g, where r is the radius of a particle, M0 is the initial mass in solids, and MMMSN is the mass in solids of a minimum-mass solar nebula at 30–150 AU. The luminosity of the dusty disk relative to the stellar luminosity is LD/L0 ∼ Lmax(t/t0)-m, where Lmax ∼ 10-3(M0/MMMSN), t0 ≈ 10–1000 Myr, and m ≈ 1–2. Our calculations produce bright rings and dark gaps with sizes Δa/a ≈ 0.1. Bright rings occur where planets 1000 km and larger have recently formed. Dark gaps are regions where planets have cleared out dust, or shadows where planets have yet to form. Planets can also grow in a planetesimal disk perturbed by the close passage of a star. Stellar flybys initiate collisional cascades, which produce copious amounts of dust. The dust luminosity following a modest perturbation is 3–4 times larger than the maximum dust luminosity of a quiescent planet-forming disk. In 10 Myr or less, large perturbations remove almost all of the planetesimals from a disk. After a modest flyby, collisional damping reduces planetesimal velocities and allows planets to grow from the remaining planetesimals. Planet formation timescales are then 2–4 times longer than timescales for undisturbed disks; dust luminosities are 2–4 times smaller.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/cb282539cf2691cace09f742d52e85c967a56a94

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In Astronomy and Astrophysics

1. A. Morbidelli
2. M. C. Wyatt
3. S. Kenyon
4. Anders Johansen
5. B. Bromley
6. D. Nesvorný
7. B. Bowler
8. M. Perryman

In Instrumentation

1. M. C. Wyatt
2. B. Bowler
3. A. Morbidelli
4. S. Kenyon
5. Michael Jura
6. B. Bromley
7. G. Kennedy
8. C. Dullemond

Citations in the corpus

• Spitzer IRS Spectroscopy of IRAS-discovered Debris Disks (2006, background): “In a minimum mass solar nebula, 1000 - 3000 km-sized bodies are expected to grow on timescales, tP ≈ 15 - 20 Myr (D/30 AU)3 (Kenyon & Bromley 2004, 2005) and to perturb planetesimals in the disk, initiating collisional cascades that produce micron-sized grains.”
• Planet Formation around Stars of Various Masses: The Snow Line and the Frequency of Giant Planets (2007, methodology): “Planet masses inferred from debris disks range from terrestrial to Jovian, at distances as great as tens of AU from the central star (e.g. Kenyon & Bromley 2004a; Greaves et al. 2005).”
• PROBING FOR EXOPLANETS HIDING IN DUSTY DEBRIS DISKS: DISK IMAGING, CHARACTERIZATION, AND EXPLORATION WITH HST/STIS MULTI-ROLL CORONAGRAPHY (2014, background): “Recently formed terrestrial planets can generate copious quantities of dust in the early phases of planetary system formation (Kenyon & Bromley 2004).”
• WIDE-FIELD INFRARED SURVEY EXPLORER OBSERVATIONS OF THE EVOLUTION OF MASSIVE STAR-FORMING REGIONS (2012, background): “These are likely the result of disks replenished in small dust by collisions between planet-size bodies, and are thus formed by second generation dust, while transition disks are evolved primordial disks that have been cleaned in their inner parts (Currie et al. 2008; Kenyon & Bromley 2004).”
• Imaging Extrasolar Giant Planets (2016, background): “…structures in disks — clumps, asymmetries, warps, gaps, rings, truncated edges, spiral arms, and geometric offsets — can also be used to indirectly infer the presence of unseen planets and predict their masses and locations (e.g., Wyatt et al. 1999; Ozernoy et al. 2000; Kenyon & Bromley 2004).”
• The Size Distribution of Kuiper Belt Objects (2004, methodology): “APPENDIX Kenyon & Luu (1998, 1999a) and Kenyon & Bromley (2001, 2002, 2004) describe algorithms and tests of our multiannulus planet formation code.”
• Steady State Evolution of Debris Disks around A Stars (2007, background): “Since planet formation models predict that such massive bodies take longer to form further from the star (Kenyon & Bromley 2004), that interpretation makes the prediction that the radius of the belts should increase with stellar age, and more recent surveys have also considered the evolution of…”
• Toward Planetesimals: Dense Chondrule Clumps in the Protoplanetary Nebula (2008, background): “Model studies (e.g., Petit et al 2001, Kenyon and Bromley 2004, 2006; Bottke et al 2005; Chambers 2004,2006; Weidenschilling and Cuzzi 2006) suggest that the collisional stage occurred after dispersal of the nebula gas allowed the orbital eccentricities of primitive bodies to grow.”
• Nearby Debris Disk Systems with High Fractional Luminosity Reconsidered (2006, background): “Most recent models link the temporal evolution of debris disks to the formation and erosion of planetesimals (Kenyon & Bromley 2002, 2004).”
• Cold Disks: Spitzer Spectroscopy of Disks around Young Stars with Large Gaps (2007, background): “If replenishment processes such as fragmentation occur preferentially in the innermost region due to higher temperatures and densities (Kenyon & Bromley 2004), this might be sufficient to produce the fraction of a lunar mass needed close to the star.”
• Planet formation and migration (2005, background): “…the original planetesimals, such as has been produced in calculations directed towards explaining the distribution of Kuiper belt objects, by Kenyon & Bromley (2004), may remain and damp the velocity dispersions, reducing both evolution times and the orbital eccentricities of the remaining…”
• Variations on Debris Disks: Icy Planet Formation at 30-150 AU for 1-3 M☉ Main-Sequence Stars (2008, methodology): “Startingwith an ensemble of P 1 km sized planetesimals, Kenyon & Bromley (2002b, 2004a, 2004b, 2005) show that collisions and mergers form 500Y1000 km sized objects in 1Y50 Myr.”
• Planet formation by coagulation: A focus on Uranus and Neptune (2004, background): “Hence s is likely much smaller than 1 km. Collisional fragmentation has been considered by Inaba, Wetherill & Ikoma (2003), Kenyon & Bromley (2004) and Rafikov (2003e).”
• Scenarios for the Origin of the Orbits of the Trans-Neptunian Objects 2000 CR105 and 2003 VB12 (Sedna) (2004, background): “Our current understanding of the collisional growth of distant objects (Kenyon & Bromley 2004) seems to exclude this possibility, because 2003 VB12 would take 4 Gyr to grow to its current size on a circular orbit at this distance, and longer be- yond.”
• Characterization of Dusty Debris Disks: The IRAS and Hipparcos Catalogs (2006, background): “Najita & Williams (2005) consider in some detail planet formation models of Kenyon & Bromley (2004a, 2004b).”