Central Bureau for Astronomical Telegrams
IAUC 4991: 1989c1; JUPITER
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Circular No. 4991
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
COMET AUSTIN (1989c1)
M. Fulle, Osservatorio Astronomico, Trieste; and L. Pansecchi,
Osservatorio di San Vittore, Bologna, write: "Around the date of
the earth crossing through the plane of the comet orbit (June 6.8
UT), geometrical circumstances will be favorable for the so-called
'neck-line structure' to appear in the dust tail of comet Austin.
Such a structure should appear as a strong dust streamer within the
main tail, having a short, thin, sunward spike lying inside the
comet orbit with respect to the sun. Similar structures were
already detected in comet Bennett 1970 II (Pansecchi et al. 1987,
A.Ap. 176, 358) and P/Halley 1986 III (Cremonese and Fulle 1989,
Icarus 80, 267). Following are listed the date; the latitude of
the earth on the plane of the comet orbit; the predicted position
angles of the 'neck line' and of the sunward spike; the synchrone
ejection time for the streamer, measured in days before perihelion;
and the sky-projected length of the sunward spike, which is
directly proportional to the dust ejection velocity from the inner
coma and is computed for a velocity of 10 m/s and given both in
units of 10E6 km and arcmin: June 2.0 UT, -12.9 deg, 327 deg, 146
deg, 12 days, 0.14, 11'; June 5.0, -4.3 deg, 332 deg, 152 deg, 12
days, 0.14, 10'; June 6.0, -1.8 deg, 333 deg, 153 deg, 11 days,
0.15, 9'; June 7.0, +0.5 deg, 335 deg, 155 deg, 11 days, 0.15, 9';
June 8.0, +2.7 deg, 336 deg, 156 deg, 11 days, 0.15, 9'; June 9.0,
+4.6 deg, 338 deg, 158 deg, 11 days, 0.15, 9'; June 12.0, +9.0 deg,
342 deg, 163 deg, 11 days, 0.16, 8'; June 17.0, +14.3 deg, 347 deg,
169 deg, 10 days, 0.16, 7'; June 22.0, +17.9 deg, 352 deg, 173 deg,
10 days, 0.17, 6'; June 27.0, +20.2 deg, 355 deg, 177 deg, 9 days,
0.18, 5'. The orbital elements on IAUC 4972 were used for these
calculation. Deep red or infrared photographs (calibrated if
possible) would be useful for analyzing the dust in the comet,
though the moon will be a problem during the best geometrical times."
JUPITER
I. Tabe, Goto Optical, Tokyo, telexes that observations of the
bright spot at latitude +24 deg (cf. IAUC 4967) by I. Miyazaki, K.
Horikawa, T. Akutsu, M. Sato, and K. Yamamoto during Feb. 10-22
indicate a very short rotation period of 9h46m55s +/- 2s, corresponding
to a wind speed of -150 m/s relative to System III. On Mar.
4.565 UT, T. Sata, Science University of Tokyo, using the 1.88-m
reflector of Okayama Astrophysical Observatory (+ CCD camera at 890
nm, the methane absorption band), found this to be the brightest spot
on the planet's disk, indicating a high altitude.
1990 April 10 (4991) Daniel W. E. Green
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