Streaming instability
In planetary science a streaming instability is a hypothetical mechanism for the formation of planetesimals in which the drag felt by solid particles orbiting in a gas disk leads to their spontaneous concentration into clumps which can gravitationally collapse.[1]
A protoplanetary disk is made up of a mix of gas and solid particles. The gas is partially supported by a pressure gradient and orbits the central star at a sub-Keplerian velocity.[2] As a result, particles orbiting through this gas feel a headwind causing them to lose momentum due to aerodynamic drag and spiral toward the star.[3] When localized clusters of closely orbiting particles form, however, they can push the gas ahead of them and thus feel less total drag than they would as individual particles.[2] The clusters therefore are able to orbit faster than individual particles and experience less radial drift toward the star.[4] The clusters grow and form filaments as they catch up with individual particles in the same orbit and as other particles spiral inward to their orbit.[5] Under the right conditions,[6][7] the filaments can grow massive enough to fragment into clouds of particles which collapse forming planetesimals the size of large asteroids or Kuiper belt objects.[8] The collapsing clouds with excess angular momentum may fragment and form binary objects.[9] After forming these planetesimals can continue to grow by accreting more of the solid particles.[10] The streaming instabilities is one of a number of possible mechanism for overcoming the various barriers to planetesimal formation via the local concentration of solids.[11]
References
- ^ "Planetesimal formation". Lund University. Retrieved 16 December 2015.
- ^ a b Johansen, A.; Youdin, A. N.; Lithwick, Y. (2011). "Rapid Accretion of Large Planetesimals by Gravitational Instabilities" (PDF). Workshop on Formation of the First Solids in the Solar System. LPI Contribution No. 1639: 9080.
- ^ Johansen, Anders; Oishi, Jeffrey S.; Mac Low, Mordecai-Mark; Klahr, Hubert; Henning, Thomas; Youdin, Andrew (2007). "Rapid planetesimal formation in turbulent circumstellar disks". Nature. 448 (7157): 1022–1025. doi:10.1038/nature06086.
- ^ Yang, Chao-Chin; Johansen, Anders (2014). "On the Feeding Zone of Planetesimal Formation by the Streaming Instability". The Astrophysical Journal. 792 (2): 86. doi:10.1088/0004-637X/792/2/86.
- ^ deCarrera, Daniel; Johansen, Anders; Davies, Melvyn B. (2015). "How to form planetesimals from mm-sized chondrules and chondrule aggregates". Astronomy & Astrophysics. 579: A43. doi:10.1051/0004-6361/201425120.
- ^ Drążkowska, J.; Dullemond, C. P. (2014). "Can dust coagulation trigger streaming instability?". Astronomy & Astrophysics. 572: a78. doi:10.1051/0004-6361/201424809.
- ^ Krijt, Sebastiaan; Ormel, Chris W.; Dominik, Carsten;; Tielens, Alexander G. G. M. (2015). "A panoptic model for planetesimal formation and pebble delivery" (PDF). arxiv eprint.
{{cite journal}}: CS1 maint: extra punctuation (link) CS1 maint: multiple names: authors list (link) - ^ Johansen, A.; Youdin, A. N.; Lithwick, Y. (2012). "Adding particle collisions to the formation of asteroids and Kuiper belt objects via streaming instabilities". Astronomy & Astrophysics. 537: A125. doi:10.1051/0004-6361/201117701.
- ^ Nesvorný, David; Youdin, Andrew N.; Richardson, Derek C. (2010). "Formation of Kuiper Belt Binaries by Gravitational Collapse". The Astronomical Journal. 140 (3): 785–793. doi:10.1088/0004-6256/140/3/785.
- ^ Johansen, Anders; Klahr, Hubert (2011). "Planetesimal Formation Through Streaming and Gravitational Instabilities". Earth, Moon, and Planets. 108 (1): 39–43. doi:10.1007/s11038-010-9370-3.
- ^ Johansen, A.; Blum, J.; Tanaka, H.; Ormel, C.; Bizzarro, M.; Rickman, H. (2014). "The Multifaceted Planetesimal Formation Process". Protostars and Planets VI: 547–570. doi:10.2458/azu_uapress_9780816531240-ch024.