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THE ASTRONOMER Electronic Circular No 3169      2016 May 19 10.47UT
Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise,  Basingstoke,
Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074
INTERNET: GUY@TAHQ.DEMON.CO.UK      Backup: gmh@wdcc1.bnsc.rl.ac.uk
WORLD WIDE WEB                         http://www.theastronomer.org
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NEPTUNE

M. H. Wong, University of California at Berkeley and others report that they
detected a dark spot on Neptune at wavelengths < 600 nm, in images taken
with the Hubble Space Telescope (+ WFC3/UVIS) on May 16 UT.  This confirms
the existence of a dark spot first imaged by WFC3/UVIS on 2015 Sept. 18 UT
as part of the OPAL program (Simon et al. 2015, Ap.J. 812, 55).  

They provisionally refer to the feature as SDS-2015 (southern dark spot
discovered in 2015). SDS-2015 was centred at planetographic latitude 45
degrees south in 2015 and at 46 degrees south in 2016, and was observed at
longitude about 138 deg west on 2016 May 16.178 UT.  The width is at least
14 deg of longitude.  Longer- wavelength data reveal the continued presence
of bright companion clouds associated with SDS-2015, supporting the
interpretation that it is an anti-cyclonic vortex (e.g., Smith et al. 1989,
Science 246, 1422).  The Hubble observing team also includes I. de Pater, J.
Tollefson, K. de Kleer, H. Hammel, S. Cook, R. Hueso, A. Sanchez-Lavega, M.
Delcroix, L. Sromovsky, G. Orton, and C. Baranec.

CBET 4278 issued 2016 May 17

Guy M Hurst