3. Condensation and Agglomeration of Grains

Arnold, Jochen

doi:10.1017/s0252921100070494

Cited by 2 publications

(1 citation statement)

References 6 publications

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“…Larson and Starrfield 1971) for the cloud. The larger particles in the system will thus grow during collapse of the cloud, and a substantial proportion of the smallest grains will accrete into systematically larger particles (Burke and Silk 1976;Arnold 1977;Kessel'man 1978Kessel'man , 1979. Insofar as the chemistry of a collapsing protostellar cloud differs in detail from that in a dense molecular cloud (Fegley and Prinn 1989;Van Dishoeck et al 1993;Prinn 1993), so too any molecular ices condensing on or within these prestellar grain aggregates will reflect the conditions of their formation.…”

Section: Protostellar Collapsementioning

confidence: 99%

Formation of Outer Solar System Bodies: Comets and Planetesimals

Bailey

1994

Symp. - Int. Astron. Union

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Abstract.Observations of massive, extended discs around both pre-main-sequence and main-sequence stellar systems indicate that protoplanetary discs larger than the observed planetary system are a common phenomenon, while the existence of large comets suggests that the total cometary mass is much greater than previous estimates. Both observations suggest that theories of the origin of the solar system are best approached from the perspective provided by theories of star formation, in particular that the protoplanetary disc may have extended up to ~103 AU. A model with a surface density distribution similar to a minimum-mass solar nebula, but extending further in radius, is derived by considering the gravitational collapse of a'uniform, slowly rotating molecular cloud. The boundary of the planetary system is determined not by lack of mass, as in previous 'mass-limited' models (i.e. those with a sharp decrease in surface density Σ beyond the radius of the observed planetary system), but instead by the increasing collision time between the comets or planetesimals initially formed by gravitational instability beyond the planetary zone. Bodies formed beyond ~50 AU have sizes on the order of 10 km and represent a collisionally unevolved population; they are composed of relatively small, unaltered clumps of interstellar dust and ices with individual sizes estimated to range up to ~10m. By contrast, bodies formed closer in, for example in the Uranus-Neptune zone, consist of larger agglomerations of dust and ices with individual sizes ranging up to ~1 km. Planetesimals formed by gravitational instability at smaller heliocentric distances r are typically much smaller than those formed furth*er out, the masses m p being proportional to Σ 3 Γ 6 , but subsequent collisional aggregation in the planetary region is expected to produce bodies with sizes ranging up to 10 2 km or more. In both cases the first-formed solid objects may be identified with observed cometary nuclei; some accumulate to produce the outer planets, but the majority are ejected, either to interstellar space or into the Oort cloud. Observed comets represent a dynamically well-mixed group from various sources; they are expected to comprise a heterogeneous mix of both pristine and relatively altered material and to have a broad mass distribution ranging up to the size of the largest planetesimals.

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Section: Protostellar Collapsementioning

confidence: 99%

Formation of Outer Solar System Bodies: Comets and Planetesimals

Bailey

1994

Symp. - Int. Astron. Union

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Meteorite research

Wood¹,

Motylewski²

1979

Reviews of Geophysics

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Meteorites contain a record of events and processes in the three earliest stages of solar system history: (1) formation of the raw material that was to become the solar system; (2) processing of the condensable component of this material in a nebular disk that circled the protosun; and (3) processing of condensed material after it had accumulated into planetesimals of asteroidal dimension. To test our acumen, the record has been written in cryptic rather than plain language. Progress toward breaking the cipher, made in the U.S. during the period 1975–1978, is summarized below. Much of the record in meteorites is contained in patterns of isotope abundances. This particular field of research is admirably reviewed by Podosek [1978].

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3. Condensation and Agglomeration of Grains

Cited by 2 publications

References 6 publications

Formation of Outer Solar System Bodies: Comets and Planetesimals

Formation of Outer Solar System Bodies: Comets and Planetesimals

Meteorite research

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