News - April 2000
04/28/2000
- New Discovery!:
Terry Lovejoy has just discovered a probable Kreutz sungrazer in C3 images of the
SOHO/LASCO coronagraph. This will be SOHO-111. The comet has not yet been announced
officially by the CBAT.
(Sungrazer Homepage)
04/22/2000
- The recovered periodic comet Kowal-Mrkos received the number 143 and is now
designated as comet 143P/Kowal-Mrkos. The current list of peridic comet codes
(which were observed at least at two apparitions) can be found
here!
- The last LINEAR comet is of short period as previously suspected. The comet
P/2000 G1 (LINEAR) has a period of about 5.4 years.
04/15/2000
- Recovery!:
On Mar. 09, 2000, the LINEAR project
discovered an apparently asteroidal object, designated 2000 ET90, which
showed - after linkage with observations of Mar. 13, Apr. 04 and 08 by LINEAR - an
cometary orbit. Single observations of Feb. 07 (LINEAR), Mar. 01 (Catalina Sky
Survey) and Apr. 02 (LONEOS) were also linked to the object. No cometary appearance
was reported by all observers. Brian G. Marsden and Carl W. Hergenrother proposed
independently the identity of 2000 ET90 with comet
D/1984 H1 (Kowal-Mrkos) which was shown to be true. Comet
P/1984 H1 = 1984 JD = 2000 ET90 (Kowal-Mrkos) passed only 0.16 AU
from Jupiter in 1989 and was not observed at its second return in 1991. The
correction to the prediction amounts to -125 days. The 16.5m comet will
pass its perihelion on Jul. 01, 2000, at about 2.5 AU. The orbital period is about 9
years. (IAUC 7403, MPEC 2000-G52)
04/14/2000
- M.D. Hicks, B.J. Buratti, R.L. Newburn and D.L. Rabinowitz (Caltech,JPL) report
in "Physical observations of 1996 PW and 1997 SE5: Extinct comets or D-type
asteroids?" (ICARUS, 2000, 143, 2, pp.354-359) about
investigations of 1996 PW and 1997 SE5, two asteroids with comet-like orbits. The
spectroscopy of both objects showed moderately red, featureless spectra typical of
the D-type asteroids, cometary nuclei, and other extinct cometary candidates. Both
objects now join (3552) Don Quixote and (944) Hidalgo as established candidates for
extinct comet nuclei.
(Abstract)
04/09/2000
- New Discovery!:
The LINEAR project discovered its
44th comet on Apr. 07, 2000. The 17m comet
C/2000 G1 (LINEAR) passed its perihelion on Mar. 09, 2000, at about 1.0 AU.
The comet is intrinsically faint since he did not get brighter than maybe
15m although being only 0.15 AU from Earth in early March but at a high
southern declination. It is very likely that this comet is of short period. (IAUC
7396)
04/06/2000
- An analysis of magnetometer data from the ESA/NASA Ulysses spacecraft of Spring
1996 should - according to the authors - provide an explanation of some of the
reported tail lengths of comet C/1996 B2 (Hyakutake) which exceeded the
phase angle. G. H. Jones and A. Balogh (Imperial College, London) and T. S. Horbury
(Queen Mary and Westfield College, London) report in Nature (404, 574) not
only the longest ever recorded tail length of a comet but also the risky conclusion
that the tail showed a curvature which should enable an earthbound observer to
detect tail lengths exceeding the phase angle. An independent detection was made by
a team lead by George Gloeckler (University of Maryland) which is also reported in
Nature.
(Ulysses Latest News and Images,
ESA Press Release,
Ulysses Page at Imperial College,
IAUC 7395)
The doubtfulness of these conclusions - especially for the time of the observed
extreme taillengths - was demonstrated by Andreas Kammerer at the International
Workshop for Cometary Astronomy (IWCA II) in August 1999 in Cambridge (England).
His conclusions can be found on these pages.
04/04/2000
- New Discovery!:
The SOHO comet which was discovered by Jon Shanklin and me on Apr. 01, 2000, received
an orbit and the designation C/2000 F1 (SOHO). It is a member of the
Kreutz group.
(IAUC 7393, MPEC 2000-G18,
Sungrazer Homepage)
04/01/2000
- This morning a SOHO sungrazer (probably SOHO-110) was discovered by Jon Shanklin
and me (and probably others) in C2 images.