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Pre-discovery Activity of New Interstellar Comet 2I/Borisov Beyond 5 AU

Ye, Quanzhi and Kelley, Michael S. P. and Bolin, Bryce T. and Bodewits, Dennis and Farnocchia, Davide and Masci, Frank J. and Meech, Karen J. and Micheli, Marco and Weryk, Robert and Bellm, Eric C. and Christensen, Eric and Dekany, Richard and Delacroix, Alexandre and Graham, Matthew J. and Kulkarni, Shrinivas R. and Laher, Russ R. and Rusholme, Ben and Smith, Roger M. (2019) Pre-discovery Activity of New Interstellar Comet 2I/Borisov Beyond 5 AU. . (Unpublished)

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Comet 2I/Borisov, the first unambiguous interstellar comet ever found, was discovered at ∼3 au from the Sun on its inbound leg. No pre-discovery detection beyond 3 au has yet been reported, mostly due to the comet's proximity to the Sun as seen from the Earth. Here we present a search for pre-discovery detections of comet Borisov using images taken by the Catalina Sky Survey (CSS), Pan-STARRS and Zwicky Transient Facility (ZTF), with a further comprehensive follow-up campaign being presented in Bolin et al. (2019). We identified comet Borisov in ZTF images taken in May 2019 and use these data to update its orbit. This allowed us to identify the comet in images acquired as far back as December 2018, when it was ∼8 au from the Sun. This suggests that the activity of the comet is driven by a more volatile species other than H₂O, such as CO or CO₂. The comet was not detected in November 2018 when it was 8.5 au from the Sun, possibly implying an onset of activity around this time. We derive the radius of the nucleus to be <7 km using the non-detection in November 2018, and estimate an area of ∼0.5-10km² has been active between December 2018 and September 2019, though this number is model-dependent and is highly uncertain. The behavior of comet Borisov during its inbound leg is observationally consistent with dynamically new comets observed in our solar system, suggesting some similarities between the two.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription Paper
Ye, Quanzhi0000-0002-4838-7676
Kelley, Michael S. P.0000-0002-6702-7676
Bodewits, Dennis0000-0002-2668-7248
Farnocchia, Davide0000-0003-0774-884X
Masci, Frank J.0000-0002-8532-9395
Meech, Karen J.0000-0002-2058-5670
Micheli, Marco0000-0001-7895-8209
Bellm, Eric C.0000-0001-8018-5348
Graham, Matthew J.0000-0002-3168-0139
Kulkarni, Shrinivas R.0000-0001-5390-8563
Laher, Russ R.0000-0003-2451-5482
Rusholme, Ben0000-0001-7648-4142
Additional Information:The authors thank G. Helou, M.-T. Hui, M. M. Knight and Z.-Y. Lin for helpful discussions and comments. MSPK acknowledges support from NASA grant NNX17AK15G. DF conducted this research at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. Based on observations obtained with the Samuel Oschin 48-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grant No. AST-1440341 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. Pan-STARRS is supported by the National Aeronautics and Space Administration under Grant No. 80NSSC18K0971 issued through the SSO Near Earth Object Observations Program. Software: ZChecker (Kelley et al. 2019) Facilities: PO:1.2m, PS1, SO:1.5m
Group:Infrared Processing and Analysis Center (IPAC), Zwicky Transient Facility
Funding AgencyGrant Number
Infrared Processing and Analysis Center (IPAC)UNSPECIFIED
Weizmann Institute of ScienceUNSPECIFIED
Stockholm UniversityUNSPECIFIED
University of Maryland UNSPECIFIED
University of WashingtonUNSPECIFIED
Deutsches Elektronen-SynchrotronUNSPECIFIED
Humboldt UniversityUNSPECIFIED
Los Alamos National LaboratoryUNSPECIFIED
University of Wisconsin-MilwaukeeUNSPECIFIED
Lawrence Berkeley National LaboratoryUNSPECIFIED
Subject Keywords:comets: individual (2I/Borisov)
Record Number:CaltechAUTHORS:20191121-083851194
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99978
Deposited By: Tony Diaz
Deposited On:21 Nov 2019 17:31
Last Modified:21 Nov 2019 17:31

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