Abstract/Details

## The evolution of comets and the detectability of extra-solar Oort Clouds

Stern, Sol Alan.
University of Colorado at Boulder ProQuest Dissertations Publishing,  1989. 9024872.

### Abstract (summary)

According to "standard" theory, comets are natural products of solar system formation, ejected to the Oort Cloud by gravitational scattering events during the epoch of giant planet formation. Stored far from the Sun for billions of years, comets almost certainly contain a record of the events which occurred during (and perhaps even before) the epoch of planetary formation.

This dissertation has two themes: an examination of the evolutionary processes that affect comets in the Oort Cloud, and a search for evidence of Extra-Solar Oort Clouds (ESOCs).

With regard to cometary evolution in the Oort Cloud, it was found that luminous O stars and supernovae have heated the surface layers of all comets on numerous occasions to 20-30 K and perhaps once to 50 K. Interstellar medium (ISM) interactions blow small grains out of Oort Clouds, and erode the upper few hundred g cm$\sp{-3}$ of material from cometary surfaces. Collisions do not significantly affect the population structure of the Cloud. However, particularly in the denser regions of the Cloud, collisions promote the development of a cometary surface regolith. If comet clouds are common, cometary mass loss due to erosion, collisions, and heating may affect the chemical balance of the ISM. The findings presented here contradict the standard view that comets do not undergo physical change in the Oort Cloud.

A logical consequence of the intimate connection between the Oort Cloud and our planetary system is that the detection of comet clouds around other stars would strongly indicate the sites of extant extra-solar planetary systems. A search was conducted for infrared IR emission from debris in ESOCs. After examining 17 stars using the Infrared Astronomical Satellite data base, only upper limits on ESOC emission could be set. In a separate study, it was found that many of the signatures of ESOC sublimation predicted to occur around luminous, post main sequence (POMS) stars are strongly reminiscent of the actual, observed attributes of Mira and OH/IR stars, indicating that the process of POMS-induced comet cloud sublimation may have already been observed. If this is confirmed by additional observations, then Oort Clouds are likely to be common.

### Indexing (details)

Subject
Astronomy;
Astrophysics
Classification
0606: Astronomy
0606: Astrophysics
Identifier / keyword
Pure sciences
Title
The evolution of comets and the detectability of extra-solar Oort Clouds
Author
Stern, Sol Alan
Number of pages
322
Degree date
1989
School code
0051
Source
DAI-B 51/04, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
979-8-207-79730-4
Brandt, John C.
University/institution
University location
Degree
Ph.D.
Source type
Dissertation or Thesis
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
9024872
ProQuest document ID
303694081