Identification

Title

Mass loss, destruction and detection of sun-grazing and -impacting cometary nuclei

Abstract

Context. Sun-grazing comets almost never re-emerge, but their sublimative destruction near the sun has only recently been observed directly, while chromospheric impacts have not yet been seen, nor impact theory developed. Aims. We seek simple analytic models of comet destruction processes near the sun, to enable estimation of observable signature dependence on original incident mass Mo and perihelion distance q. Methods. Simple analytic solutions are found for M(r) versus q and distance r for insolation sublimation and, for the first time, for impact ablation and explosion. Results. Sun-grazers are found to fall into three (Mo,q) regimes: sublimation-, ablation-, and explosion-dominated. Most sun-grazers have Mo too small (<10¹¹ g) or q too large (>1.01R⊙) to reach atmospheric densities (n > 2.5 × 10¹¹/cm³) where ablation exceeds sublimation. Our analytic results for sublimation are similar to numerical models. For q < 1.01R⊙,Mo > 10 ¹¹ g, ablation initially dominates but results are sensitive to nucleus strength Pc = 10⁶P₆ dyne/cm² and entry angle φ to the vertical. Nuclei with Mo ≼ 10¹⁰(P6secφ)3 g are fully ablated before exploding, though the hot wake itself explodes. For most sun-impactors secφ ≫ 1 (since q ~ r∗), so for q very close to r∗ the ablation regime applies to moderate g impactors unless P₆ ≼ 0.1. For higher masses, or smaller q, nuclei reach densities n > 2.5 × 10¹⁴P₆/cm³ where ram pressure causes catastrophic explosion. Conclusions. Analytic descriptions define (Mo,q) regimes where sublimation, ablation and explosion dominate sun-grazer/-impactor destruction. For q ≺ 1.01R⊙,Mo ≽ 10¹¹ g nuclei are destroyed by ablation or explosion (depending on Mocos3φ/Pc) in the chromosphere, producing flare-like events with cometary abundance spectra. For all plausible Mo,q and physical parameters, nuclei are destroyed above the photosphere.

Resource type

document

Resource locator

Unique resource identifier

code

http://n2t.net/ark:/85065/d770824z

codeSpace

Dataset language

eng

Spatial reference system

code identifying the spatial reference system

Classification of spatial data and services

Topic category

geoscientificInformation

Keywords

Keyword set

keyword value

Text

originating controlled vocabulary

title

Resource Type

reference date

date type

publication

effective date

2016-01-01T00:00:00Z

Geographic location

West bounding longitude

East bounding longitude

North bounding latitude

South bounding latitude

Temporal reference

Temporal extent

Begin position

End position

Dataset reference date

date type

publication

effective date

2011-11-01T00:00:00Z

Frequency of update

Quality and validity

Lineage

Conformity

Data format

name of format

version of format

Constraints related to access and use

Constraint set

Use constraints

Limitations on public access

None

Responsible organisations

Responsible party

contact position

OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

name: homepage

responsible party role

pointOfContact

Metadata on metadata

Metadata point of contact