Central Bureau for Astronomical Telegrams
IAUC 5624: 1992v; SATURN VI (TITAN)
The following International Astronomical Union Circular may be linked-to from your own Web pages, but must not otherwise be redistributed (see these notes on the conditions under which circulars are made available on our WWW site).
Read IAUC 5625
.dvi or
.ps format.
Circular No. 5624
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM EASYLINK 62794505
MARSDEN@CFA or GREEN@CFA (.SPAN, .BITNET or .HARVARD.EDU)
PERIODIC COMET GEHRELS 3 (1992v)
J. V. Scotti, Lunar and Planetary Laboratory, reports his
recovery of this comet with the Spacewatch telescope at Kitt Peak.
The object is of stellar appearance and the position is in close
agreement with the prediction on MPC 16381 (ephemeris on MPC 20171).
1992 UT R.A. (2000) Decl. m1
Sept.26.44826 5 25 12.80 +23 08 19.1 22.0
26.45819 5 25 12.99 +23 08 19.8
28.45122 5 26 02.94 +23 08 35.5
28.46007 5 26 03.06 +23 08 35.3
28.47270 5 26 03.43 +23 08 35.7 21.6
SATURN VI (TITAN)
M. T. Lemmon and E. Karkoschka, Lunar and Planetary Laboratory,
University of Arizona, report: "We observed Titan on July 18 and
19 at the Steward Observatory 2.3-m telescope and on Sept. 13, 14,
15, and 17 at the Multiple Mirror Telescope, using the Ge Spectrograph
(range 0.85-1.35 microns, resolution 0.01 micron; calibration
done relative to the nearby star SAO 164338). While Titan's
spectral shape remained constant throughout our observing periods in
regions of medium and strong methane absorption, we see significant
variations in continuum wavelengths. In the continuum regions of
1.08 and 1.28 microns, Titan is 14 and 22 percent brighter,
respectively, on Sept. 13 and 14 (when it was near eastern elongation)
with respect to July 18 and 19 (near western elongation). A small
observed brightness increase at 0.94 micron is less certain, due to
interference from telluric absorption. The continuum albedos for
Sept. 15 are below those for Sept. 13 and 14; by Sept. 17, when
only the 1.28-micron region was observed, the continuum albedo was
consistent with the July observations. Our atmospheric models of
Titan indicate that the observed spectral variations derive from
clouds below 10 km altitude, or, more likely, from the surface. If
we indeed see the surface, we can constrain surface albedo
variations and Titan's rotational period. At 1.08 and 1.28 microns,
Titan has an average surface albedo near 0.2, and the minimum to
maximum variations are at least 0.1. Our data are consistent with
a synchronous rotational period of 16 days, but can also be fit
with certain rotational periods from 5 to 18 days."
1992 September 28 (5624) Daniel W. E. Green
Read IAUC 5625
.dvi or
.ps format.
Our Web policy. Index to the CBAT/MPC/ICQ pages.
