Central Bureau for Astronomical Telegrams
IAUC 3215: 1977 UB; P/JACKSON-NEUJMIN; Occns BY URANIAN RINGS
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Read IAUC 3216
Circular No. 3215
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Cable Address: SATELLITES, NEWYORK Telex: 921428
Telephone: (617) 864-5758
1977 UB
Further precise positions have been reported as follows:
UT R. A. (1950) Decl. Mag. Observer
1945 Apr. 16.85713 11 48 11.67 - 2 35 48.9 16 Niemi
1978 Jan. 9.05209 1 55 16.05 +11 08 21.1 19 West
10.04936 1 55 15.80 +11 08 16.4 "
A. Niemi (Turku Observatory). Very weak image identified near the
plate limit.
R. M. West (European Southern Observatory). 100-cm Schmidt.
PERIODIC COMET JACKSON-NEUJMIN
The following ephemeris, by B. G. Marsden, is from the elements
in Handb. Br. Astron. Assoc. for 1978. Because of difficulty
linking the apparitions the uncertainty in T is as much as +/- 2 days.
For dT = +1d
1978/79 ET R. A. (1950) Decl. Delta r dR.A. dDecl. m2
June 21 17 43.39 - 0 18.4 1.471 2.438 -1m58 - 0'7 21.2
July 1 17 33.49 - 0 18.6 -1.57 - 0.9
11 17 24.05 - 0 44.3 1.383 2.291 -1.53 - 0.9 20.8
21 17 16.23 - 1 34.7 -1.47 - 0.8
31 17 10.97 - 2 46.9 1.375 2.145 -1.39 - 0.4 20.5
Aug. 10 17 08.92 - 4 16.2 -1.32 + 0.1
20 17 10.43 - 5 57.6 1.417 2.002 -1.27 + 0.7 20.3
30 17 15.58 - 7 46.1 -1.23 + 1.4
Sept. 9 17 24.33 - 9 37.4 1.480 1.864 -1.23 + 2.0 20.1
19 17 36.56 -11 27.4 -1.24 + 2.7
29 17 52.11 -13 12.4 1.544 1.736 -1.28 + 3.2 19.8
Oct. 9 18 10.84 -14 48.7 -1.35 + 3.6
19 18 32.56 -16 12.5 1.600 1.621 -1.43 + 3.8 19.6
29 18 57.06 -17 20.1 -1.52 + 3.8
Nov. 8 19 24.14 -18 07.5 1.649 1.527 -1.63 + 3.5 19.4
18 19 53.44 -18 31.2 -1.74 + 3.0
28 20 24.58 -18 28.5 1.698 1.461 -1.84 + 2.3 19.3
Dec. 8 20 57.13 -17 57.5 -1.93 + 1.3
18 21 30.56 -16 58.0 1.759 1.428 -1.99 + 0.1 19.3
28 22 04.39 -15 31.2 -2.03 - 1.1
Jan. 7 22 38.19 -13 40.2 1.842 1.433 -2.04 - 2.3 19.4
m2 = 16.5 + 5 log Delta + 10 log r
OCCULTATIONS BY URANIAN RINGS
Further analysis, by the undersigned, of the occultation of
SAO 158687 on 1977 Mar. 10 yields the following radii for the rings,
assumed to lie in Uranus' equatorial plane (cf. IAUC 3051, 3061):
Ring Distance Ring Distance
alpha 44 835 km delta 48 408 km
beta 45 788 epsilon1 51 697
gamma 47 732 epsilon2 51 030
These results (uncertainty +/- 30 km) are very similar to those by
Wasserman et al. (1977, Bull. Am. Astron. Soc. 9, 498).
As the result of observations of another predicted occultation
on 1977 Dec. 23 (IAUC 3108; Astron. J. 1977, 82, 849, 929, 1036),
Millis and Wasserman (1978, Astron. J. to be published) confirm the
existence of the gamma, delta and epsilon rings and possibly also of the
alpha ring; these measurements, obtained at a wavelength of 0.88 um at
Cabezon Observatory, Tenerife, were difficult to make in the dawn sky.
E. Persson, Hale Observatories; P. Nicholson, K. Matthews, P.
Goldreich and G. Neugebauer, California Institute of Technology,
report that successful observations at a wavelength of 2.2 um were
made with the 250-cm du Pont telescope at the Las Campanas
Observatory on 1978 Apr. 10 of a third occultation by the Uranian rings
(only the occultation by Uranus itself could be detected in the
case of a fainter star on 1978 Apr. 4). All five 'original' rings
were detected, and assuming the above values for the alpha, beta, gamma and
delta rings the radii of further rings were determined as follows:
Ring Distance Ring Distance
kappa1 42 029 km kappa2 42 148 km
iota1 42 394 iota2 42 304
theta1 42 660 theta2 42 696
eta1 47 290 eta2 47 289
epsilon1 50 848 epsilon2 51 402
As before (IAUC 3051, 3061), subscripts refer to the western and
eastern edges of the rings, respectively. The kappa ring is uncertain.
The iota1 and theta1 events are undoubtedly identical with the alpha3 and
beta3 events previously described by Millis et al. (IAUC 3051). The eta
events were also subsequently reported by L. Elliot (unpublished)
in the case of the SAO 158687 occultation.
The more recent results for epsilon suggest that this is indeed a
complete ring but that its width is relatively substantial, its
shape non-circular and its structure complex. The possible zeta ring
of J. Churms (IAUC 3051) has not been confirmed, and there appear
to be no confirmed rings of any consequence outside epsilon.
1978 May 1 (3215) Brian G. Marsden
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