Circular No. 4867 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 or GREEN@CFA.BITNET MARSDEN or GREEN@CFAPS2.SPAN NEPTUNE Further to IAUC 4806 and 4824, the Voyager Imaging Team reports the discovery of two more satellites, 1989 N5 and 1989 N6, in Voyager 2 narrow-angle imaging data. Each was observed in at least 25 frames over a time span of 11 days, during which the measurement error was about 150 km per narrow-angle pixel or smaller. The root-mean-square post-fit residuals are of the order of a single narrow-angle camera pixel. The orbits are direct, and that of 1989 N5 appears to be nearly circular and equatorial. The orbit of 1989 N6 is circular but has an inclination of about 4.5 deg. The revolution periods are 0.31 and 0.29 days, and the mean radial distances are about 50 000 km and 48 200 km, respectively. Preliminary calculations indicate that 1989 N5 is about one visual magnitude fainter than 1989 N3 in the Voyager 2 narrow-angle clear filter and that 1989 N6 is two magnitudes fainter than 1989 N3. Estimated diameters for the satellites 1989 N1-1989 N6 are thus 420, 200, 140, 160, 90, and 50 km, respectively. It also appears that the ring arcs mentioned on IAUC 4830 are in fact complete rings, although the outer ring contains prominent arclike sections. The rings have radial distances of 62 900 and 52 300 km, and the earlier designations are to be replaced by 1989 N1R and 1989 N2R. The Voyager Imaging Team also reports a broader ring, 1989 N3R, some 1500-2000 km wide and centered at 41 900 km from Neptune's center. The designation 1989 N4R is given to diffuse sheet, extending all the way inward from a distance of about 57 500 km, while 1989 N5R refers to a relatively narrow feature at the outer edge of this sheet. It is now virtually certain that the satellite 1989 N2 is identical with 1981 N1 (cf. IAUC 3608), despite an earlier suggested categorization of 1981 N1 as a ring arc (cf. IAUC 4022), rather than as a satellite. It appears probable, however, that 1984 N1 (cf. IAUC 3962, 3968) is associated with one of the arclike structures in the ring 1989 N1R. JUPITER Revision to IAUC 4863. M. Ressler and M. Shure (University of Hawaii) observed Jupiter on 1989 Aug. 4. IRTF staff observers included W. Golish, D. Griep, and C. Kaminski. 1989 September 29 (4867) Daniel W. E. Green
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