Comet 46P/Wirtanen is passing through the southern sky constellation of Fornax in November 2018 and reaches southernmost declination on 2018-Nov-03. Sky motion has slowed and is near its minimum of 0.13 arcsec/minute. The position angle of a dust tail as it develops should shift during November. When the dust tail lengthens beyond the coma it is expected to develop some curvature, since the r and - v position angle vectors are near perpendicular. If an ion tail develops it should appear as a thin tail pointing away from the sun.
The coma of 46P was recently measured at 15 arc minutes in diameter and should increase noticeably during the month as the distance between Earth and comet decreases from 0.269 AU on 2018-Nov-02 to 0.120 AU on 2018-Dec-01. The coma is diffuse with stars visible inside as has been reported by Chris Wyatt. Color images should show an enlarging blue-green gas coma from CN, C3, and C2 emission. Visually a Swan filter can be used to enhance contrast as has been reported by Chris Wyatt.
Total visual magnitude has been steadily brightening from near magnitude 8.2 reported by Paul Camilleri on 2018-Nov-02 to about 5th magnitude by 2018-Dec-01 using either the 46P light curve by S. Yoshida or COBS.
Nuclear magnitudes have been steadily brightening from near magnitude 13.8 reported by J. G. Bosch on 2018-Oct-29 to about 11th magnitude by 2018-Dec-01.
R band Afrho measurements reported by the Spanish Comets-Obs group also show steadily increasing values which have ranged between 40 to 60 cm for aperture radius of 10,000 km during October 2018.
Water production was detected by Dave Schleicher at Lowell Observatory on 2018-Oct-06. Dave Schleicher detected OH using narrowband filter photometry on 6 October (r=1.38 AU). Haser models gave an OH production of Q(OH)=2.0×10^27 molecules/s. This converts to a water production rate of Q(H2O)=2.3×10^27 molecules/s or . Production rates for other species on the same date: Q(CN)=4.5×10^24 molecules/s, Q(C2)= 6.3×10^24 molecules/s, and Afrho(5260A) = 20 cm. See the UMd comet Wirtanen web pages for more info.
Edited by cbellh47, 03 November 2018 - 05:52 AM.
