Debris disks detected in HST archival images of young stars, HD 141943 and HD 191089, using improved imaging processes (24 April 2014).[1]486958 Arrokoth, the first pristine planetesimal visited by a spacecraft.
A widely accepted theory of planet formation, the so-called planetesimal hypothesis of Viktor Safronov, states that planets form from cosmic dust grains that collide and stick to form ever-larger bodies. Once a body reaches around a kilometer in size, its constituent grains can attract each other directly through mutual gravity, enormously aiding further growth into moon-sized protoplanets. Smaller bodies must instead rely on Brownian motion or turbulence to cause the collisions leading to sticking. The mechanics of collisions and mechanisms of sticking are intricate.[2][3] Alternatively, planetesimals may form in a very dense layer of dust grains that undergoes a collective gravitational instability in the mid-plane of a protoplanetary disk—or via the concentration and gravitational collapse of swarms of larger particles in streaming instabilities.[4] Many planetesimals eventually break apart during violent collisions, as 4 Vesta[5] and 90 Antiope may have,[6] but a few of the largest ones may survive such encounters and grow into protoplanets and, later, planets.
Planetesimals in the Solar Systemedit
It has been inferred that about 3.8 billion years ago, after a period known as the Late Heavy Bombardment, most of the planetesimals within the Solar System had either been ejected from the Solar System entirely, into distant eccentric orbits such as the Oort cloud, or had collided with larger objects due to the regular gravitational nudges from the giant planets (particularly Jupiter and Neptune). A few planetesimals may have been captured as moons, such as Phoebe (a moon of Saturn) and many other small high-inclination moons of the giant planets.
Planetesimals that have survived to the current day are valuable to science because they contain information about the formation of the Solar System. Although their exteriors are subjected to intense solar radiation that can alter their chemistry, their interiors contain pristine material essentially untouched since the planetesimal was formed. This makes each planetesimal a 'time capsule', and their composition might reveal the conditions in the Solar Nebula from which our planetary system was formed. The most primitive planetesimals visited by spacecraft are the contact binaryArrokoth.[7]
Definition of planetesimaledit
The word planetesimal is derived from the word infinitesimal and means an ultimately small fraction of a planet. [citation needed]
While the name is always applied to small bodies during the process of planet formation, some scientists also use the term planetesimal as a general term to refer to many small Solar System bodies – such as asteroids and comets – which are left over from the formation process. A group of the world's leading planet formation experts decided at a conference in 2006[8] on the following definition of a planetesimal:
A planetesimal is a solid object arising during the accumulation of orbiting bodies whose internal strength is dominated by self-gravity and whose orbital dynamics is not significantly affected by gas drag. This corresponds to objects larger than approximately 1 km in the solar nebula.
Bodies large enough not only to keep together by gravitation but to change the path of approaching rocks over distances of several radii start to grow faster. These bodies, larger than 100 km to 1000 km, are called embryos or protoplanets.[9]
In the current Solar System, these small bodies are usually also classified by dynamics and composition, and may have subsequently evolved[10][11][12] to become comets, Kuiper belt objects or trojan asteroids, for example. In other words, some planetesimals became other types of body once planetary formation had finished, and may be referred to by either or both names.
The above definition is not endorsed by the International Astronomical Union, and other working groups may choose to adopt the same or a different definition. The dividing line between a planetesimal and protoplanet is typically framed in terms of the size and the stages of development that the potential planet has already gone through: planetesimals combine to form a protoplanet, and protoplanets continue to grow (faster than planetesimals).[13][14][15]
^Harrington, J.D.; Villard, Ray (24 April 2014). "RELEASE 14-114 Astronomical Forensics Uncover Planetary Disks in NASA's Hubble Archive". NASA. from the original on 2014-04-25. Retrieved 2014-04-25.
^Blum, Juergen; Wurm, Gerhard (2008). "The Growth Mechanisms of Macroscopic Bodies in Protoplanetary Disks". Annual Review of Astronomy and Astrophysics. 46. Annual Reviews: 21–56. Bibcode:2008ARA&A..46...21B. doi:10.1146/annurev.astro.46.060407.145152.
^Singh, Chamkor; Mazza, Marco (2018). "Early-stage aggregation in three-dimensional charged granular gas". Physical Review E. 97 (2): 022904. arXiv:1710.11496. Bibcode:2018PhRvE..97b2904S. doi:10.1103/PhysRevE.97.022904. PMID 29548210. S2CID 3895707.
^Polak, Brooke; Klahr, Hubert (2023-02-01). "High-resolution Study of Planetesimal Formation by Gravitational Collapse of Pebble Clouds". The Astrophysical Journal. 943 (2). arXiv:2211.13318. doi:10.3847/1538-4357/aca58f.
^Savage, Don; Jones, Tammy; Villard, Ray (1995). "Asteroid or Mini-Planet? Hubble Maps the Ancient Surface of Vesta". Hubble Site News Release STScI-1995-20. Retrieved 2006-10-17.
^Marchis, Franck; Enriquez, J. E.; Emery, J. P.; Berthier, J.; Descamps, P. (2009). The Origin of the Double Main Belt Asteroid (90) Antiope by Component-Resolved Spectroscopy. DPS meeting #41. American Astronomical Society. Bibcode:2009DPS....41.5610M.
^Jeff Moore, New Horizons press release, NASA TV, 2 January 2019
^Workshop From Dust to Planetesimals 2006-09-07 at the Wayback Machine
^ Morbidelli, A. "Origin and dynamical evolution of comets and their reservoirs". arXiv.
^ Gomes, R., Levison, H. F., Tsiganis, K., Morbidelli, A. 2005, "Origin of the cataclysmic Late Heavy Bombardment period of the terrestrial planets". Nature, 435, 466–469.
^ Morbidelli, A., Levison, H. F., Tsiganis, K., Gomes, R. 2005, "Chaotic capture of Jupiter's Trojan asteroids in the early Solar System". Nature, 435, 462–465.
^Leinhardt, Zoë M.; Richardson, Derek C. (2005-05-20). "Planetesimals to Protoplanets. I. Effect of Fragmentation on Terrestrial Planet Formation". The Astrophysical Journal. 625 (1): 427. doi:10.1086/429402. ISSN 0004-637X.
^Kominami, Junko; Tanaka, Hidekazu; Ida, Shigeru (2005-11-15). "Orbital evolution and accretion of protoplanets tidally interacting with a gas disk: I. Effects of interaction with planetesimals and other protoplanets". Icarus. Jovian Magnetospheric Environment Science. 178 (2): 540–552. doi:10.1016/j.icarus.2005.05.008. ISSN 0019-1035.
^"Planetesimal | Astronomy, Solar System & Planet Formation | Britannica". www.britannica.com. Retrieved 2024-01-03.
Further readingedit
Discovering the Essential Universe by Neil F. Comins (2001) [ISBN missing]
Linda T. Elkins-Tanton, et al.: Planetesimals – Early Differentiation and Consequences for Planets. Cambridge University Press, Cambridge 2017, ISBN978-1107118485.
planetesimal, this, article, needs, additional, citations, verification, please, help, improve, this, article, adding, citations, reliable, sources, unsourced, material, challenged, removed, find, sources, news, newspapers, books, scholar, jstor, september, 20. This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Planetesimal news newspapers books scholar JSTOR September 2019 Learn how and when to remove this template message Planetesimals p l ae n ɪ ˈ t ɛ s ɪ m el z are solid objects thought to exist in protoplanetary disks and debris disks Believed to have formed in the Solar System about 4 6 billion years ago they aid study of its formation Debris disks detected in HST archival images of young stars HD 141943 and HD 191089 using improved imaging processes 24 April 2014 1 486958 Arrokoth the first pristine planetesimal visited by a spacecraft Contents 1 Formation 2 Planetesimals in the Solar System 3 Definition of planetesimal 4 See also 5 Notes and references 6 Further readingFormation editA widely accepted theory of planet formation the so called planetesimal hypothesis of Viktor Safronov states that planets form from cosmic dust grains that collide and stick to form ever larger bodies Once a body reaches around a kilometer in size its constituent grains can attract each other directly through mutual gravity enormously aiding further growth into moon sized protoplanets Smaller bodies must instead rely on Brownian motion or turbulence to cause the collisions leading to sticking The mechanics of collisions and mechanisms of sticking are intricate 2 3 Alternatively planetesimals may form in a very dense layer of dust grains that undergoes a collective gravitational instability in the mid plane of a protoplanetary disk or via the concentration and gravitational collapse of swarms of larger particles in streaming instabilities 4 Many planetesimals eventually break apart during violent collisions as 4 Vesta 5 and 90 Antiope may have 6 but a few of the largest ones may survive such encounters and grow into protoplanets and later planets Planetesimals in the Solar System editIt has been inferred that about 3 8 billion years ago after a period known as the Late Heavy Bombardment most of the planetesimals within the Solar System had either been ejected from the Solar System entirely into distant eccentric orbits such as the Oort cloud or had collided with larger objects due to the regular gravitational nudges from the giant planets particularly Jupiter and Neptune A few planetesimals may have been captured as moons such as Phoebe a moon of Saturn and many other small high inclination moons of the giant planets Planetesimals that have survived to the current day are valuable to science because they contain information about the formation of the Solar System Although their exteriors are subjected to intense solar radiation that can alter their chemistry their interiors contain pristine material essentially untouched since the planetesimal was formed This makes each planetesimal a time capsule and their composition might reveal the conditions in the Solar Nebula from which our planetary system was formed The most primitive planetesimals visited by spacecraft are the contact binary Arrokoth 7 Definition of planetesimal editThe word planetesimal is derived from the word infinitesimal and means an ultimately small fraction of a planet citation needed While the name is always applied to small bodies during the process of planet formation some scientists also use the term planetesimal as a general term to refer to many small Solar System bodies such as asteroids and comets which are left over from the formation process A group of the world s leading planet formation experts decided at a conference in 2006 8 on the following definition of a planetesimal A planetesimal is a solid object arising during the accumulation of orbiting bodies whose internal strength is dominated by self gravity and whose orbital dynamics is not significantly affected by gas drag This corresponds to objects larger than approximately 1 km in the solar nebula Bodies large enough not only to keep together by gravitation but to change the path of approaching rocks over distances of several radii start to grow faster These bodies larger than 100 km to 1000 km are called embryos or protoplanets 9 In the current Solar System these small bodies are usually also classified by dynamics and composition and may have subsequently evolved 10 11 12 to become comets Kuiper belt objects or trojan asteroids for example In other words some planetesimals became other types of body once planetary formation had finished and may be referred to by either or both names The above definition is not endorsed by the International Astronomical Union and other working groups may choose to adopt the same or a different definition The dividing line between a planetesimal and protoplanet is typically framed in terms of the size and the stages of development that the potential planet has already gone through planetesimals combine to form a protoplanet and protoplanets continue to grow faster than planetesimals 13 14 15 See also editAccretion astrophysics Disrupted planet List of interstellar and circumstellar molecules Mesoplanet Planetary nebula Q PACE a spacecraft mission to study accretion Ring system astronomy Notes and references edit Harrington J D Villard Ray 24 April 2014 RELEASE 14 114 Astronomical Forensics Uncover Planetary Disks in NASA s Hubble Archive NASA Archived from the original on 2014 04 25 Retrieved 2014 04 25 Blum Juergen Wurm Gerhard 2008 The Growth Mechanisms of Macroscopic Bodies in Protoplanetary Disks Annual Review of Astronomy and Astrophysics 46 Annual Reviews 21 56 Bibcode 2008ARA amp A 46 21B doi 10 1146 annurev astro 46 060407 145152 Singh Chamkor Mazza Marco 2018 Early stage aggregation in three dimensional charged granular gas Physical Review E 97 2 022904 arXiv 1710 11496 Bibcode 2018PhRvE 97b2904S doi 10 1103 PhysRevE 97 022904 PMID 29548210 S2CID 3895707 Polak Brooke Klahr Hubert 2023 02 01 High resolution Study of Planetesimal Formation by Gravitational Collapse of Pebble Clouds The Astrophysical Journal 943 2 arXiv 2211 13318 doi 10 3847 1538 4357 aca58f Savage Don Jones Tammy Villard Ray 1995 Asteroid or Mini Planet Hubble Maps the Ancient Surface of Vesta Hubble Site News Release STScI 1995 20 Retrieved 2006 10 17 Marchis Franck Enriquez J E Emery J P Berthier J Descamps P 2009 The Origin of the Double Main Belt Asteroid 90 Antiope by Component Resolved Spectroscopy DPS meeting 41 American Astronomical Society Bibcode 2009DPS 41 5610M Jeff Moore New Horizons press release NASA TV 2 January 2019 Workshop From Dust to Planetesimals Archived 2006 09 07 at the Wayback Machine Michael Perryman The Exoplanet Handbook Cambridge University Press 2011 ISBN 978 0 521 76559 6 1 p 226 at Google Books Morbidelli A Origin and dynamical evolution of comets and their reservoirs arXiv Gomes R Levison H F Tsiganis K Morbidelli A 2005 Origin of the cataclysmic Late Heavy Bombardment period of the terrestrial planets Nature 435 466 469 Morbidelli A Levison H F Tsiganis K Gomes R 2005 Chaotic capture of Jupiter s Trojan asteroids in the early Solar System Nature 435 462 465 Leinhardt Zoe M Richardson Derek C 2005 05 20 Planetesimals to Protoplanets I Effect of Fragmentation on Terrestrial Planet Formation The Astrophysical Journal 625 1 427 doi 10 1086 429402 ISSN 0004 637X Kominami Junko Tanaka Hidekazu Ida Shigeru 2005 11 15 Orbital evolution and accretion of protoplanets tidally interacting with a gas disk I Effects of interaction with planetesimals and other protoplanets Icarus Jovian Magnetospheric Environment Science 178 2 540 552 doi 10 1016 j icarus 2005 05 008 ISSN 0019 1035 Planetesimal Astronomy Solar System amp Planet Formation Britannica www britannica com Retrieved 2024 01 03 Further reading editDiscovering the Essential Universe by Neil F Comins 2001 ISBN missing Linda T Elkins Tanton et al Planetesimals Early Differentiation and Consequences for Planets Cambridge University Press Cambridge 2017 ISBN 978 1107118485 Portals nbsp Physics nbsp Astronomy nbsp Stars nbsp Spaceflight nbsp Outer space nbsp Solar System nbsp Science Retrieved from https en wikipedia org w index php title Planetesimal amp oldid 1214482209, wikipedia, wiki, book, books, library,
