edu.ucar.opensky::articles:12072 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-26T04:09:02.998543 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d770824z Mass loss, destruction and detection of sun-grazing and -impacting cometary nuclei 2011-11-01T00:00:00Z publication https://n2t.org/ark:/85065/d770824z https://doi.org/10.1051/0004-6361/201015660 Brown, James author Potts, H. author Porter, L. author Le Chat, G. author UCAR/NCAR - Library publisher 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. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication Copyright 2011 European Southern Observatory. None eng geoscientificInformation