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  A Comet Active Beyond the Crystallization Zone

Jewitt, D., Hui, M.-T., Mutchler, M., Weaver, H., Li, J., & Agarwal, J. (2018). A Comet Active Beyond the Crystallization Zone. The Astrophysical Journal Letters, 847(2): L19.

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Item Permalink: http://hdl.handle.net/21.11116/0000-0001-35EA-C Version Permalink: http://hdl.handle.net/21.11116/0000-0007-070E-3
Genre: Journal Article

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 Creators:
Jewitt, David, Author
Hui, Man-To, Author
Mutchler, Max, Author
Weaver, Harold, Author
Li, Jing, Author
Agarwal, Jessica1, Author              
Affiliations:
1Department Planets and Comets, Max Planck Institute for Solar System Research, Max Planck Society, ou_1832288              

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Free keywords: comets: general; comets: individual (C/2017 K2, Oort Cloud)
 MPIS_PROJECTS: Ground-based Obs.
 Abstract: We present observations showing inbound long-period comet C/2017 K2 (PANSTARRS) to be active at a record heliocentric distance. Nucleus temperatures are too low (60–70 K) either for water ice to sublimate or for amorphous ice to crystallize, requiring another source for the observed activity. Using the Hubble Space Telescope we find a sharply bounded, circularly symmetric dust coma 105 km in radius, with a total scattering cross-section of ~105 km2. The coma has a logarithmic surface brightness gradient −1 over much of its surface, indicating sustained, steady-state dust production. A lack of clear evidence for the action of solar radiation pressure suggests that the dust particles are large, with a mean size greater than or similar to 0.1 mm. Using a coma convolution model, we find a limit to the apparent magnitude of the nucleus V > 25.2 (absolute magnitude H > 12.9). With assumed geometric albedo p(V) = 0.04, the limit to the nucleus circular equivalent radius is <9 km. Prediscovery observations from 2013 show that the comet was also active at 23.7 au heliocentric distance. While neither water ice sublimation nor exothermic crystallization can account for the observed distant activity, the measured properties are consistent with activity driven by sublimating supervolatile ices such as CO2, CO, O2, and N2. Survival of supervolatiles at the nucleus surface is likely a result of the comet's recent arrival from the frigid Oort Cloud.

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Language(s): eng - English
 Dates: 2018-04-252018
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Degree: -

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Title: The Astrophysical Journal Letters
  Other : Astrophys. J. Lett.
Source Genre: Journal
 Creator(s):
Affiliations:
Publ. Info: Chicago, IL : University of Chicago Press for the American Astronomical Society
Pages: - Volume / Issue: 847 (2) Sequence Number: L19 Start / End Page: - Identifier: ISSN: 0004-637X
CoNE: https://pure.mpg.de/cone/journals/resource/954922828215