Central Bureau for Astronomical Telegrams
IAUC 4022: Prob. RING OF NEPTUNE (1984 N1, 1981 N1); 1983 TB
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 4023
Circular No. 4022
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM Telephone 617-495-7244/7440/7444
PROBABLE RING OF NEPTUNE (1984 N1, 1981 N1)
W. B. Hubbard, Lunar and Planetary Laboratory, reports that
his analysis of data from the Neptune appulse on July 22 confirms
the report by Manfroid et al. (IAUC 3962, 3968) of an occultation
event. Data obtained at Cerro Tololo by F. Vilas and L.-R. Elicer
show a very similar occultation profile with a duration of ~ 2 s,
occurring at 5h40m09s UT, and with a maximum decline of ~ 35 percent
in the stellar intensity at 0.8 ;m. Cerro Tololo is ~ 100 km
south of the European Southern Observatory, and since the shadow
width at each site does not exceed a few tens of km, the occulting
object was probably a ring segment. Further, Hubbard's reeexamination
of observations by T. Gehrels, J.-A. Gehrels and M. Waterworth
of the 1983 June 15 Neptune occultation at Hobart, Tasmania,
shows a single shallow event at 14h02m with a duration of 27 s and
a maximum decline of 2.5 percent. This also corresponds to an
object in Neptune's equatorial plane about 3 radii from the planet's
center, and the integrated equivalent width was similar to that in
1984. These data imply that Neptune possesses a single ring at a
distance of ~ 76 400 km from its center. All data so far available
show only single events, rather than paired ring crossings.
Thus the ring width apparently varies greatly with longitude and/
or time, the variation frequently being great enough to make the
ring's optical depth undetectably small. The event reported on
IAUC 3608 was presumably also associated with the ring.
1983 TB
Visual magnitude estimates: Dec. 12.33 UT, 12.9 (A. Hale,
near Mt. Wilson, CA); 17.98, 12.9 (J. Bortle, Stormville, NY).
Examination for possible cometary activity with large telescopes as
the object approaches perihelion is urged. Ephemeris continuation:
1984/85 ET R.A. (1950.0) Decl. p r Mag.
Dec. 11 3 38.81 +37 37.0
16 2 31.92 +32 06.1 0.262 1.195 14.2
21 1 23.44 +22 46.8
26 0 24.43 +11 40.3 0.253 1.042 14.7
31 23 38.17 + 1 34.1
Jan. 5 23 02.19 - 6 24.4 0.324 0.868 15.6
10 22 32.81 -12 27.0
15 22 06.96 -17 02.6 0.435 0.667 16.2
1984 December 21 (4022) Brian G. Marsden
Read IAUC 4023
Our Web policy. Index to the CBAT/MPC/ICQ pages.
