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A New Dark Vortex on Neptune

Wong, Michael H. and Tollefson, Joshua and Hsu, Andrew I. and de Pater, Imke and Simon, Amy A. and Hueso, Ricardo and Sánchez-Lavega, Agustín and Sromovsky, Lawrence and Fry, Patrick and Luszcz-Cook, Statia and Hammel, Heidi and Delcroix, Marc and de Kleer, Katherine and Orton, Glenn S. and Baranec, Christoph (2018) A New Dark Vortex on Neptune. Astronomical Journal, 155 (3). Art. No. 117. ISSN 1538-3881.

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An outburst of cloud activity on Neptune in 2015 led to speculation about whether the clouds were convective in nature, a wave phenomenon, or bright companions to an unseen dark vortex (similar to the Great Dark Spot studied in detail by Voyager 2). The Hubble Space Telescope (HST) finally answered this question by discovering a new dark vortex at 45 degrees south planetographic latitude, named SDS-2015 for "southern dark spot discovered in 2015." SDS-2015 is only the fifth dark vortex ever seen on Neptune. In this paper, we report on imaging of SDS-2015 using HST's Wide Field Camera 3 across four epochs: 2015 September, 2016 May, 2016 October, and 2017 October. We find that the size of SDS-2015 did not exceed 20 degrees of longitude, more than a factor of two smaller than the Voyager dark spots, but only slightly smaller than previous northern-hemisphere dark spots. A slow (1.7–2.5 deg/year) poleward drift was observed for the vortex. Properties of SDS-2015 and its surroundings suggest that the meridional wind shear may be twice as strong at the deep level of the vortex as it is at the level of cloud-tracked winds. Over the 2015–2017 period, the dark spot's contrast weakened from about -7% to about -3%, while companion clouds shifted from offset to centered, a similar evolution to some historical dark spots. The properties and evolution of SDS-2015 highlight the diversity of Neptune's dark spots and the need for faster cadence dark spot observations in the future.

Item Type:Article
Related URLs:
URLURL TypeDescription
Wong, Michael H.0000-0003-2804-5086
Hsu, Andrew I.0000-0002-6190-9336
de Pater, Imke0000-0002-4278-3168
Simon, Amy A.0000-0003-4641-6186
Hueso, Ricardo0000-0003-0169-123X
Sánchez-Lavega, Agustín0000-0001-7355-1522
Sromovsky, Lawrence0000-0001-5480-8580
Fry, Patrick0000-0002-7367-6541
Hammel, Heidi0000-0001-8751-3463
Delcroix, Marc0000-0002-9828-7390
de Kleer, Katherine0000-0002-9068-3428
Orton, Glenn S.0000-0001-7871-2823
Baranec, Christoph0000-0002-1917-9157
Additional Information:© 2018. The American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2017 November 21; revised 2017 December 22; accepted 2017 December 29; published 2018 February 15. Based on observations associated with programs GO-13937, GO-14044, GO-14334, GO-14492, and GO-14756, with support provided by NASA through grants from the Space Telescope Science Institute (operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555). Data were obtained from the Data Archive at the Space Telescope Science Institute. Support was provided by the National Science Foundation through grant AST-1615004 and by the NASA Earth and Space Science Fellowship through grant NNX16AP12H to I.dP. and J.T., and by the Alfred P. Sloan Foundation and the National Science Foundation through grant AST-1712014 to C.B. We acknowledge support from grants AYA2015-65041-P (MINECO/FEDER, UE), Grupos Gobierno Vasco IT-765-13, and UPV/EHU UFI11/55 to A.S.L. and R.H. We thank an anonymous reviewer for their quick and constructive review. Facility: HST(WFC3). - Software: Astroconda, IDL, L.A.Cosmic, WinJUPOS, JPL Horizons Ephemerides.
Group:Astronomy Department
Funding AgencyGrant Number
NASANAS 5-26555
NASA Earth and Space Science FellowshipNNX16AP12H
Alfred P. Sloan FoundationUNSPECIFIED
Ministerio de Economía, Industria y Competitividad (MINECO)AYA2015-65041-P
Fondo Europeo de Desarrollo Regional (FEDER)UNSPECIFIED
Grupos Gobierno VascoIT-765-13
University of the Basque Country (UPV/EHU)UFI11/55
Subject Keywords:astrometry; hydrodynamics; planets and satellites: atmospheres; planets and satellites: gaseous planets; planets and satellites: individual (Neptune) ; techniques: high angular resolution
Issue or Number:3
Record Number:CaltechAUTHORS:20190424-103159951
Persistent URL:
Official Citation:Michael H. Wong et al 2018 AJ 155 117
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:94917
Deposited By: George Porter
Deposited On:24 Apr 2019 17:56
Last Modified:20 Apr 2020 08:47

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