BAA Comet Section : Comets 1998
Updated 2000 August 20
When observing a comet please try to forget how bright you think the comet
should be, what it was when you last viewed it, what other observers think
it is or what the ephemeris says it should be.
The equations for the light curves of comets that are currently visible
use only the raw observations and should give a reasonable prediction for
the current brightness. If the comet has not yet been observed or has
gone from view a correction for aperture is included, so that telescopic
observers should expect the comet to be fainter than given by the equation.
The correction is about 0.033 per centimetre. Values for the r parameter
given in square brackets [ ] are assumed. The form of the light curve is
either the standard m = H0 + 5 log d + K0 log r or the linear brightening
m = H0 + 5 log d + L0 abs(t - T + D0) where T is perihelion, t the present
and D0 an offset, if L0 is +ve the comet brightens towards perihelion and
if D0 is +ve the comet is brightest prior to perihelion.
Comet 21P/Giacobini-Zinner,
the parent comet of the October
Draconid meteors, should be visible from August until the end
of the year, brightening from 14m to 9m. It is an evening
object and at its best at the end of November. Starting off
in Hercules and accelerating into Aquila, it then moves
through the zodiacal constellations of Capricornus and
Aquarius. An increasingly southern declination means that UK
observers will loose it towards the end of the year. The
comet was first discovered by Michael Giacobini at Nice observatory
in December 1900 and was thought to have a period of 6.8
years. The next two returns were expected to be difficult to
observe, but in October 1913, Ernst Zinner, of Bamberg, Germany,
discovered a comet whilst observing variable stars in Scutum.
This turned out to be the same comet, but the period had been
incorrectly determined. The comet was missed at three
unfavourable returns, so this will be the thirteenth
apparition of the comet.
The comet is currently around 9th mag and readily visible to UK
observers. Martin Mobberley
imaged the comet on October 14 and
October 25 .
Observations received so far (50) give an uncorrected preliminary
light curve of
8.7 + 5 log d + 16.3 log r
Observations in ICQ format, last observation
1998 October 26, updated 1998 November 4 .
Comet 29P/Schwassmann-Wachmann 1
is now in conjunction. Andrew Pearce reports glimpsing
it at 14th mag in his 0.41-m reflector at the end of December 1997. Further
reports suggest that the comet brightened to around 12th mag visually and
then faded to 14th mag. The second outburst of the year commenced in mid March
according to IAUC 6844 and the comet is now around 13th mag, though I was unable
to see it on April 28.9, when it was fainter than 13.2. It may be undergoing
another outburst at around 13th mag (May 30).
This annual comet has frequent outbursts and over the past couple of years
seems to be more often active than not, though it rarely gets brighter
than 12m. It is possible that its pattern of behaviour is changing. In early
1996 it was in outburst for several months. The randomly spaced
outbursts may be due to a thermal heat wave propagating into the
nucleus and triggering sublimation of CO inside the comet.
The comet will be observable in Libra for the
rest of the year. This comet is an ideal target for those equipped
with CCDs and it should be observed at every opportunity.
Observations in ICQ format, updated 1998 May 21 .
Comet 43P/Wolf-Harrington is now too
faint for visual observation at this return.
This was the ninth observed return of the comet, which was discovered
in 1924, then lost until 1951. The comet is in a chaotic orbit, and
made a close approach to Jupiter in 1936 which reduced its perihelion
distance from 2.4 to 1.6 AU. At the last return the comet reached
13m.
Observations received so far (33) give an uncorrected preliminary
light curve of
9.3 + 5 log d + 12.9 log r
Observations in ICQ format, last observation
1998 January 31, updated 1998 February 4 .
Comet 52P/Harrington-Abel was found in
outburst at 12th mag by Alain Maury, Observatoire de la Cote d'Azur,
on CCD images taken on July 21.1 UT when its predicted
magnitude was about 21. [IAUC 6975, 1998 July 25]. It is currently visible in
the morning sky at around 13th mag (October 18), but is slowly fading despite
its decreasing distance from the sun, with perihelion not occuring until 1999.
A second outburst may have occured some 80 days before perihelion.
Observations received so far (12) give an uncorrected preliminary
light curve of
15.1 + 5 log d - 0.0328 abs(t - T + 31.7)
Observations in ICQ format, last observation
1998 November 1, updated 1998 November 4 .
Comet 62P/Tsuchinshan 1 is no longer visible
at this apparition.
Observations received so far (5) give an uncorrected preliminary
light curve of
7.2 + 5 log d + [10] log r
Observations in ICQ format, last observation
1998 May 19, updated 1998 October 5 .
Comet 69P/Taylor was brighter
than expected, reaching 12th mag.
A series of Jupiter encounters last century reduced q from 3.1
to 1.6 AU and led to its discovery by Clement Taylor from South Africa in
December 1915. It was quite bright, 9th magnitude at best, and shortly
after perihelion split into two fragments, each with a short tail. The
secondary nucleus became brighter than the primary, but then rapidly faded
and the primary also faded more rapidly than expected. The comet was then
lost until 1977, when new orbital computations led to the recovery of the
B component by Charles Kowal with the Palomar Schmidt. The A component
was not found.
Observations received so far (60) show an uncorrected preliminary
light curve given by an initial brightening up to mid February, peaking
at 12th mag, followed by a decline of
8.1 + 5 log d + 7.5 log r
Observations in ICQ format, last observation
1998 May 31, updated 1998 October 5 .
Comet 78P/Gehrels 2 is now too
faint for visual observation.
Observations received so far (72) don't give a very good fit after mid February,
but up till then the uncorrected preliminary light curve is
8.2 + 5 log d + [10] log r
Observations in ICQ format, last observation
1998 February 2 (or possibly April 24), updated 1998 June 26 .
Comet 88P/Howell
With a low inclination orbit, the
comet sticks to the zodiacal constellations and can be found
in Scorpius at perihelion, moving onwards to Capricornus at
the end of the year. UK observers will loose it after early
June, after which it belongs to more southerly located
observers. The comet was discovered in 1981 by Ellen Howell
with the 0.46-m Palomar Schmidt. It passed 0.6 AU from
Jupiter in 1978, which reduced the perihelion distance, but
the biggest change to its orbit occurred in 1585 when an
encounter reduced q from 4.7 to 2.4 AU.
I made a tentative observation of the comet on May 29.95, estimating
it at 13.5: with the Northumberland refractor. My observations
prior to mid May appear unlikely and should be treated as upper
limits. Recent observations put it at around 10th magnitude. It seems
to be another comet with a linear light curve peaking after perihelion.
Observations received so far (18) give an uncorrected preliminary
light curve of
8.2 + 5 log d + 0.0315 abs(t - T - 52.1)
Observations in ICQ format, last observation
1998 October 19, updated 1998 November 4 .
Comet 93P/Lovas 1 is slowly
brightening and is currently around 14th mag.
Observations in ICQ format, last observation
1998 November 1, updated 1998 November 4 .
Comet 103P/Hartley 2
is now too faint for visual observation.
In 1982 the comet made a close approach to Jupiter, and it was
discovered by Hartley four years later, around nine months after
perihelion. It was accidently recovered by T V Kryachko of Majdanak,
USSR, on 1991 July 9.85, returning 5.6 days earlier than predicted.
It was well observed by the section at this return and observations
showed that the brightness peaked around 13 days after perihelion.
This return is also a good one and for the northern hemisphere it is
likely to be the brightest predicted periodic comet of the year. It
is an evening object throughout the apparition and slowly brightens
reaching 9m in late December when it is at perihelion. It will
then slowly fade, but should remain observable until April. The
orbit comes close to that of the Earth and it could produce a meteor
shower at the descending node in November. Calculations by Harold
Ridley gave a radiant of 19h56m +14, some 5 deg Nf Altair, with a
likely maximum around November 17.
See also information from the IMO
Observations received so far (289) give an uncorrected preliminary light curve of
8.5 + 5 log d + 18.4 log r
or
8.3 + 5 log d + 0.042 abs (T-16.8) where T is the number of days after perihelion
nearly identical with that from the previous apparition
Observations in ICQ format, last observation
1998 April 24, updated 1998 June 26
Comet 104P/Kowal 2
is no longer visible this apparition.
Observations received so far (37) give a preliminary light curve of
10.5 + 5 log d + 11.0 log r
Observations in ICQ format, last observation
1998 April 23, updated 1998 October 5
Comet 1995 O1 Hale-Bopp
is visible in the evening sky in large binoculars for observers south of the equator.
It was a 'great comet', though in some ways comet Hyakutake made a
greater impression with its long straight gas tail.
The most recent
observations by Albert Jones, using a large reflector put it at 10th mag, whilst those
by Jose Aguiar give around 9.5 in a 0.23-m reflector.
This analysis of the comet's light
curve, coma diameter and tail length was made for the TA special supplement on
the comet which was published in the autumn of 1997.
Over the entire apparition (697 days with observations, spread over 1108 days)
the comet has the corrected lightcurve :
-0.73 + 5 log d + 7.81 log r
There are significant variations from this, and the comet is currently nearly
a magnitude fainter than indicated by this equation.
For more information on the comet see the
CBAT or
ESO
pages.
1995 observations (9kb) /
1996 observations (113kb) /
1997 observations (Jan - April) (126kb) /
1997 observations (May - December) (38kb) /
1998 observations (10kb) in
ICQ format, last observation 1998 August 5, updated 1998 October 5.
1997 BA6 Spacewatch
Details of the orbit of an unusual asteroid, 1997 BA6 were given on
MPEC C-13. The orbit is very eccentric, with a period near 4500
years and a semi-major axis of several hundred AU. This is more
typical of a long period comet and subsequent observations with large
telescopes showed a small faint coma. Currently it is nearly 16th
mag and will be at high southern dec
when near perihelion. It is heading for perihelion at 3.4
AU in 1999 December when it may be around 12th mag.
1997 D1 Mueller
was discovered on plates taken by Jean Mueller for the
2nd Palomar Sky Survey with the 1.2m Oschin Schmidt Camera on 1997 Feb
17th. The object was reported as 16th mag, but appeared brighter to
visual observers. It is no longer within visual range.
Observations received so far (52) give an uncorrected preliminary light curve of
9.5 + 5 log d + [5] log r
though this is a very poor fit and a better fit is given by
8.0 + 5 log d + [7.5] log r until October, followed
by a fade of around 0.5 magnitude per month.
Observations in ICQ format, last observation
1998 January 27 (or possibly February 19), updated 1998 May 27
55P/Tempel-Tuttle (1997 E1)
was recovered by observers using the Keck 10m telescope and confirmed using
the ESO 3.5m NTT at mag 22. It passed relatively close to the earth in late
January, but is now receding from us and the sun. It is no longer observable
at this return. Here is some historical information on the comet.
Observations received so far (184) give an uncorrected preliminary light curve of
8.5 + 5 log d + 26.7 log r
or
7.8 + 5 log d + 0.072 (T+4.4) where T is the number of days after perihelion
Observations in ICQ format, last observation
1998 March 8, updated 1998 October 5
1997 G2 Montani
was announced on IAUC 6626. It is an 18th mag object, again reported
by Joe Montani of the Spacewatch team. The comet was predicted to
brighten to 16th mag at perihelion in April.
1998 G3 SOHO
New astrometric measurements and orbital elements for C/1998
G3 (SOHO-47) (cf. IAUC 6952) appear on MPEC 2000-A37. This comet is also
not a Kreutz sungrazer. [IAUC 7343, 2000 January 10]
1997 J2 Meunier-Dupouy
French amateur Michel Meunier reported a comet 6' SW of 1997 J1 on
1997 May 7.9, moving more slowly and perhaps 0.5 mag brighter.
Independently another pair of French amateurs P Dupouy and J F
Lahitte reported it the next day. The comet is quite distant.
The comet is at a good solar elongation, though
rather too low in the sky for UK observers.
The comet seemed significantly fainter on August 6.1 when I made it 13.0. It seems
to appear brighter in reflectors and on August 14.9 I made it 12.0 in my 0.33-m L
x75.
Observations received so far (283) give an uncorrected preliminary light curve of
5.4 + 5 log d + 7.0 log r
The observations are fairly well scattered.
Observations in ICQ format, last observation
1998 October 19, updated 1998 November 4
1997 T1 Utsunomiya
Syogo Utsunomiya of Azamihara, Minami-Oguni cho, Aso-gun, Kumamoto-ken, Japan
visually discovered a mag 10.5 comet, strongly condensed with a 2' coma
diameter using 25x150B on October 3.6. [IAUC 6751, 1997 October 5].
The comet should have
been brighter than 12th mag throughout 1997 September and may be visible on patrol
photographs. It is no longer visible.
Observations received so far (130) give an uncorrected preliminary light curve of
5.6 + 5 log d + 22.2 log r
Observations in ICQ format, last observation
1998 May 31, updated 1998 October 5
1998 A1 SOHO (IAUC 6811, 1998 January 23)
1998 E1 SOHO (IAUC 6837, 1998 March 11)
1998 F1 SOHO (IAUC 6862, 1998 April 4)
1998 G2 SOHO (IAUC 6879, 1998 April 18)
1998 G4 SOHO (IAUC 6952, 1998 June 25)
1998 H2 SOHO (IAUC 6952, 1998 June 25)
1998 J2 SOHO (IAUC 6952, 1998 June 25)
1998 K7 SOHO (IAUC 6952, 1998 June 25)
1998 K8 SOHO (IAUC 6952, 1998 June 25)
1998 K9 SOHO (IAUC 6952, 1998 June 25)
1998 K10 SOHO (IAUC 6952, 1998 June 25)
1998 K11 SOHO (IAUC 6952, 1998 June 25)
1998 L1 SOHO (IAUC 6984, 1998 August 5)
1998 M7 SOHO (IAUC 6984, 1998 August 5)
1998 V1 SOHO (IAUC 7435, 2000 June 2)
were discovered with the SOHO LASCO coronographs and have not been observed
elsewhere. They were sungrazing comets and were not expected to survive perihelion.
More 1997 SOHO comets have been reported on IAUC 6811, IAUC 6813, IAUC 6825 and
IAUC 6837.
SOHO-54 and 55 were visible on the same images.
The initial uncertainty in the orbit of 1998 J1 suggests that there may be a problem with
the transfer of the co-ordinate reference frame from the LASCO coronographs.
C/ designation of any new objects will not be made until accurate positions and hence
orbits are available.
Information about the latest discoveries is available from
LASCO comet observations web site.
SOHO experienced a malfunction on 1998 June 25 and contact
with it was lost. It was located by radar on July 29, communication was established
in early August and it resumed pointing at the Sun in mid
September. The LASCO cameras were reactivated in October
so there is the possibility that it may discover more comets, and some may also
be found on archival images.
There are three LASCO (Large Angle Spectroscopic Coronographs) on the SOHO spacecraft.
C1 has a field from 1.1 to 3 solar radii, C2 from 1.5 to 6 and C3 from 3.5 to 30.
Brighter objects are often discovered in the real time data, but the fainter ones
have to wait for the archival data to be searched which runs three or four months behind.
SOHO has now discovered 55 comets (5 were not sungrazers), and they are
probably not all members of the same Kreutz group.
Further background information on the SOHO comets can be found from the
LASCO comet observations web site.
If you look at the
LASCO real-time movies,
you will see the latest 2 bright sungrazers in the C2 field at the same time.
1998 B1 135P/Shoemaker-Levy 8
has been recovered by Carl Hergenrother with the SAO 1.2-m reflector at Mt Hopkins
on January 22 when it was 22nd magnitude [IAUC 6821, 1998 February 9].
The comet is unklikely to become bright enough for visual observation.
1998 G1 P/LINEAR
was discovered during survey work by the Lincoln Laboratory Near Earth Asteroid
Research Project using the Lincoln Laboratory ETS 1-m f2.15 reflector on April 2.13
[IAUC 6863, 1998 April 6]. The asteroidal object had a retrograde near parabolic orbit
and further images by Warren Offutt of Cloudcroft, New Mexico showed a tail but no
coma. Further observations have shown that it is in a Halley type orbit, with a
period of 41.5 years. The comet was around 18th mag, but
won't become much brighter than 17th mag as the return is not a favourable one.
1998 G3 SOHO
This SOHO comet (SOHO-47) was not a Kreutz sungrazer, and faded very rapidly.
A movie
of it can be seen on the LASCO pages and there is more information at the
LASCO comet observations web site.
New astrometric measurements and orbital elements for C/1998
G3 (cf. IAUC 6952) appeared on MPEC 2000-A37. [iauc 7343, 2000 January 10]
1998 H1 Stonehouse
Patrick Stonehouse of Wolverine, MI, USA, reported a visual discovery, using a
0.44-m relector, of a diffuse comet with slight condensation on April 22.3. He was
observing in Serpens Caput and noticed a diffuse object which showed motion. There was
some confusion over the reported motion, but it was eventually confirmed by Alan Hale
on April 26.3 [IAUC 6883, 1998 April 26]. The discovery magnitude was given as
mag 12 - 13, though Alan Hale put it at 10.7. I observed it with the Northumberland
refractor x100 on April 28.08 and made it 11.7, coma diameter 1.1', DC s3. Nick James
imaged it on
April 28.9 and this shows a faint tail to the south. Despite moonlight I was able to
observe it with the Northumberland refractor on May 3.88, making it 12.1, DC3 and
diameter 1.1'. I was unable to see it on May 29.96, making it fainter than 13.4.
Observations received so far (73) give an uncorrected preliminary light curve of
11.0 + 5 log d + 5.0 log r
Observations in ICQ format, last observation
1998 July 31, updated 1998 October 5
1998 J1 SOHO
This SOHO comet has become the first to be observed other than by the
satellite. It was discovered by Shane Stezelberger on C3 coronagraph images on
May 3 [IAUC 6894, 1998 May 5]. Initial magnitude estimates put it at magnitude 0
or brighter, with a fan-shaped tail, some 8 degrees from the sun, however ground based
measurements suggest it is fainter than initially estimated.
It is now fainter than 12th mag.
Observations received so far (127) give an uncorrected preliminary light curve of
6.2 + 5 log d + 6.3 log r
Observations in ICQ format, last observation
1998 July 19, updated 1998 November 4
1998 K1 Mueller
Jean Mueller discovered another comet during the 2nd Palomar Sky Survey on May 16.2
with the 1.2-m Oschin Schmidt. [IAUC 6908, 1998 May 18]. It is 16th mag and expected
to fade, though the initial orbit is rather uncertain.
Observations received so far (8) give an uncorrected preliminary light curve of
? + 5 log d + ? log r
Observations in ICQ format, last observation
1998 June 25, updated 1998 October 5
1998 K2 LINEAR
was one of 37 fast moving objects discovered during survey work on May 24 by the
Lincoln Laboratory Near Earth Asteroid Research Project using the Lincoln Laboratory
ETS 1-m f2.15 reflector at Socorro, New Mexico. The MPC were able to link it with
one of 25 fast movers discovered two nights earlier. [IAUC 6915, 1998 May 25]. The
object was reported at 16th mag by LINEAR, but other observations have put it as
bright as 13th mag. It is at high southern declination and is at
perihelion in September and will be around 13th mag.
1998 K3 LINEAR
was another fast moving object discovered during survey work, on May 23, by the
Lincoln Laboratory Near Earth Asteroid Research Project with the
ETS 1-m f2.15 reflector.
On sending the first confirmatory observations on May 24.5 UT, F. B.
Zoltowski (Woomera, 0.3-m Schmidt-Cassegrain) remarked on the "poor"
nature of the images, and on May 25.5 he added that they were diffuse
and difficult to measure (unlike those of the six other LINEAR objects he
also observed at that time). Initial orbit computations at the Minor
Planet Center suggested that the orbit was retrograde. In response to
their request, M. Tichy (Klet, 0.6-m reflector), observing on May 25.9,
also remarked that the object seemed slightly diffuse (coma about 8").
In better conditions on May 26.2, W. B. Offutt (Cloudcroft, 0.6-m
reflector) remarked on a faint coma, some 3" in diameter, and a faint,
but discernible, tail extending about 10" from the central condensation
in p.a. approximately 120 deg. S. Nakano reports that A. Sugie (Dynic,
0.6-m reflector), observing on May 26.6, independently noted the object's
cometary nature, with a 6"-8" coma and a 6" tail to the east. [IAUC 6916,
1998 May 26]. The object is 17th mag and will fade.
1998 K4 136P/Mueller 3
was recovered on May 24.4 by J. V. Scotti of the Lunar and Planetary Laboratory,
with the Spacewatch telescope on Kitt Peak. The comet, of mag 21, is very
slightly diffuse, with a coma diameter of 12" on May 26.45 UT. The indicated
correction to the prediction by S. Nakano on MPC 27081 is Delta T = -0.7 day.
[IAUC 6919, 1998 May 26].
1998 K5 LINEAR
is yet another fast moving object discovered during survey work, on May 26, by the
Lincoln Laboratory Near Earth Asteroid Research Project with the
ETS 1-m f2.15 reflector.
The high orbital eccentricity indicated in the early computations was the
first clue that the object might be a comet, although there were the
complications that the orbit has a low inclination and that, when asked,
several observers felt that their data showed the object to be asteroidal
in nature. The first observational indication of cometary character was
provided by P. J. Shelus, who remarked that images obtained by J. G. Ries
(McDonald, 0.76-m reflector, poor seeing) on May 29.39 UT seemed to show
a tail to the south and west, roughly opposite the object's direction of
motion. P. Pravec (Ondrejov, 0.65-m reflector) also remarked on the tail,
consistently on co-added images and marginally on individual images, 0'.4
long in p.a. 235 deg on May 27.03, 0'.4 long in p.a. 225 deg on May 28.95
and 0'.3 long in p.a. 227 deg on May 29.97. On May 30.46 C. Veillet
(Canada-France-Hawaii, 3.6-m reflector) noted a clear 30" tail on a
1-min exposure .
S. Nakano reports that A. Sugie (Dynic, 0.6-m reflector, bad seeing),
observing on May 27.58, independently noted (on four coadded frames)
a 16" tail in p.a. 230 deg. [IAUC 6923, 1998 May 30]. The comet has a
perihelion distance just inside the Earth's orbit, but is intrinsically
very faint. The latest orbit gives a period of around 600 years.
I observed it on June 20.0 and was surprised how easy it was to see and
how rapidly it is moving. I estimated it at 12.9 in the Northumberland x170.
The motion was obvious within a minute - absolutely fascinating! It was a
similar magnitude on June 21.0 and essentially stellar in appearance. Its appearance
was little changed on June 28.98. Nick James obtained a
CCD image of
the comet on July 1.98. It was still an easy object on July 22.1 when I made it
around 13.3. It hadn't changed much in appearance by August 23.1 and was only
a little fainter though a little more diffuse in mid October. By the end of October
it was still 14th mag, but becoming larger and more diffuse. The light curve
is very unusual and the comet's absolute magnitude seems to have peaked
some 60 days after perihelion.
Observations analysed so far (56) give an uncorrected preliminary light
curve of
12.7 + 5 log d + 0.0419 abs(t - T - 61.4)
Observations in ICQ format, last observation
1998 November 1, updated 1998 November 4
1998 K6 137P/Shoemaker-Levy 2
was recovered by C. W. Hergenrother with the Smithsonian Astrophysical
Observatory's 1.2-m reflector at Mt. Hopkins on May 19. The comet appeared
stellar at 21st mag, although the observations were made through moderate
cirrus. The indicated correction to the prediction by S. Nakano on
MPC 29881 is Delta T= -0.5 day. [IAUC 6928, 1998 June 2].
1998 M1 LINEAR
was discovered during survey work by the Lincoln Laboratory Near Earth Asteroid
Research Project using the Lincoln Laboratory ETS 1-m f2.15 reflector on June 16.2
[IAUC 6940, 1998 June 16]. CCD observations suggest it is around 16th mag, but it
could be brighter to visual observers. The comet will fade.
1998 M2 LINEAR
was recorded during survey work by the Lincoln Laboratory Near Earth Asteroid
Research Project using the Lincoln Laboratory ETS 1-m f2.15 reflector on May 28.4
and discovered to be cometary on June 19.3
[IAUC 6949, 1998 June 20]. CCD observations suggest it is around 15th mag, but it
could be a little brighter to visual observers. The comet will slowly fade.
Observations analysed so far (10) give an uncorrected preliminary light curve of
? + 5 log d + ? log r
Observations in ICQ format, last observation
1998 July 31, updated 1998 October 5
1998 M3 Larsen
was discovered by J Larsen with the 0.9-m Spacewatch telescope on June 24.3
but prediscovery observations made by LINEAR were found in images taken on May 26.3.
The comet is very distant with perihelion at 5.8 AU. It is around 18th magnitude and
expected to fade.
1998 M4 LINEAR
was discovered during survey work by the Lincoln Laboratory Near Earth Asteroid
Research Project using the Lincoln Laboratory ETS 1-m f2.15 reflector on June 25.3
[IAUC 6954, 1998 June 27]. The comet is 17th mag (though possibly 14th or 15th mag
to visual observers) and will fade.
1998 M5 LINEAR
was discovered during survey work by the Lincoln Laboratory Near Earth Asteroid
Research Project using the Lincoln Laboratory ETS 1-m f2.15 reflector on June 30.3
[IAUC 6959, 1998 July 1].
I made it 13.7 on July 22.1. In an
observation on July 30.9 somewhat spoilt by cloud I estimated it at 13.3:. On August
24.9 I made it 12.5, DC4 in my 0.33-m L x75, a little brighter than in the large
refractor. Martin Mobberley imaged the comet on September 21
. By mid October the comet had brightened to around 11th mag.
The comet was at perihelion in January
and passed very close
to the pole in mid March, when it was
imaged
by David Strange. Heading south it passed through
Camelopardalus and Lynx, reaching Cancer mid year when it
had faded to 13th magnitude. It is too faint
and close to the sun for further observation.
369 observations received so far give an uncorrected preliminary light
curve of 6.1 + 5 log d + 10.1 log r
Observations in ICQ format,
last observation 1999 November 4, updated 1999 November 29.
1998 M6 Montani
was announced on IAUC 6960 [1998 July 1]. It is a 19th mag object, discovered
visually by Joe Montani on the display monitor during the course of routine
Spacewatch observations with the 0.9-m telescope. The comet is a distant one and
is expected to fade.
1998 O1 138P/Shoemaker-Levy 7 was recovered
by J. V. Scotti, Lunar and Planetary Laboratory, with the Spacewatch telescope on
Kitt Peak on July 25.4 [IAUC 6979, 1998 July 27]. The comet was around 21st mag.
The indicated correction to the
prediction by B. G. Marsden on MPC 25183 was Delta T = -0.7 day. The comet is not
expected to become significantly brighter.
1998 P1 Williams
Peter Williams of Heathcote (near Sydney) made a visual discovery of a new comet
using a 0.30-m f/6 reflector (72x) on August 10.5. [IAUC 6986, 1998 August 11].
I was able to observe it in
10x50B on several occasions in August and September 1998 whilst on a
visit to Australia
and New Zealand, making it around 7.5. It was observed from the UK after
perihelion. It is no longer visible.
121 observations received so far give an uncorrected preliminary light
curve of 6.5 + 5 log d + 10.7 log r
Observations in ICQ format,
last observation 1999 May 12, updated 1999 August 12.
1998 Q1 LINEAR
was discovered during survey work by the Lincoln Laboratory Near Earth Asteroid
Research Project using the Lincoln Laboratory ETS 1-m f2.15 reflector on August 24.3
[IAUC 6995, 1998 August 25]. The comet is 15th mag and will fade.
1998 QP54 LONEOS-Tucker was identified as a comet
by Roy A. Tucker (Tucson, AZ) whilst carrying out a CCD asteroid-astrometry
program with a 0.36-m f/11 Schmidt-Cassegrain at the Goodricke-Pigott Observatory.
G. V. Williams, Minor Planet Center, then identified the comet with 1998 QP54,
which had been reported by E. Bowell (observer W. D. Ferris, measurer
B. W. Koehn) as an apparently quite ordinary minor planet in the course of
LONEOS, the Lowell Observatory Near-Earth Object Search.
Williams then also identified single-night observations (also on Aug. 28)
by LINEAR as belonging to the same object. Information about the object
was then placed in The NEO Confirmation Page. In response, J. Ticha
reported observations made at the Klet Observatory that showed a faint coma
(diameter 17") and a 35" tail in p.a. 226 deg, and L. Sarounova reported
from the Ondrejov Observatory on a narrow tail 5' long in p.a. 135 deg and
only a small coma. Observations were also reported by T. Spahr from the
Catalina Sky Survey. The comet was named on IAUC 7024 [1998 October 6]
and will fade from its current 16th mag.
The comet is of short period, and it made a close approach to Jupiter early in 1992.
Nick James was able to image it on October 14
1998 S1 P/LINEAR-Mueller
was discovered by Jean Mueller on October 17 on a 30-min exposure taken on Oct 14
with the 1.2-m Oschin Schmidt telescope at Palomar by K. Rykoski and Mueller in
the course of Palomar Outer Solar System Ecliptic Survey. The comet was confirmed
on Oct 17 and Gareth Williams later identified it with minor planets observed by
LINEAR on Sept 26 and 27 and LONEOS on Sept 17. The comet
is of short period and had a close approach to Jupiter in 1992.
[IAUC 7031, 1998 October 19]. The comet is 14th
mag and will fade.
A/1998 SV4
This asteroid has a very short period of 0.74 years, with a high inclination
and a perihelion distance of 0.3AU. It reaches perihelion in 2001 May.
1998 T1 LINEAR
was discovered during survey work by the Lincoln Laboratory Near Earth Asteroid
Research Project using the Lincoln Laboratory ETS 1-m f2.15 reflector on October 2.3
[IAUC 7026, 1998 October 8]. The comet was one of 17 fast-moving asteroidal objects
discovered on October 2, but appears to be a long-period comet, according both to the
retrograde nature of its orbit and remarks by Y. Ikari (Moriyama, Japan) concerning
the object's appearance, when he observed it on Oct. 3 and 8 in response to a request
on The NEO Confirmation Page. Martin Mobberley obtained this
image of the comet in 1998.
Seiichi Yoshida recovered the comet in late April after conjunction
but its magnitude was fainter than expected in his CCD
images. It brightened and reached 9th mag in late June, but it has now faded below
visibility.
35 observations received so far give an uncorrected preliminary light
curve of 10.2 + 5 log d + 4.5 log r
Observations in ICQ format,
last observation 1999 July 31, updated 1999 August 31.
1998 U1 LINEAR
is yet
another comet discovered by LINEAR. The object, discovered on Oct.
18, was reported as asteroidal and fast-moving, and a request for
further observations was placed on The NEO Confirmation Page. From
the confirmatory observations, made at four observatories on Oct.
20 and 21, it quickly became clear that the object had a retrograde,
nearly parabolic orbit. Referring to the observations made with
the 0.65-m f/3.6 reflector at the Ondrejov Observatory on Oct. 20.9
UT, P. Pravec notes that a faint tail was visible on individual
3-min exposures with a clear filter. The tail, extending 16" in
p.a. 60 deg, was confirmed on co-addition of six frames. [IAUC
7033, 1998 October 21]. The comet is
faint and distant and past perihelion.
1998 U2 P/Mueller 6
was discovered by Jean Mueller on plates
taken by herself on Oct 21.3 (and with K. Rykoski on Oct. 22) with the 1.2-m Oschin
Schmidt Telescope in the course of the Palomar Outer Solar System
Ecliptic Survey. The comet has a strong condensation and a short,
faint tail to the southeast. [IAUC 7035, 1998 October 22]. Prediscovery
images from September 14 were found in LONEOS data and the comet is an
intrinsically faint periodic object found at a favourable opposition.
1998 U3 P/Jager
was discovered by Michael Jager on 16- and 9-min
Technical Pan film exposures with a 0.25-m f/2.8 Schmidt camera.
The comet has a 1'-2' coma with condensation and a tail several
arcmin long in p.a. 275-281 deg and is around 12th mag. [IAUC 7038,
1998 October 25]. It is at perihelion in early December and will
brighten a little before slowly fading.
I observed it on October 29.1,
making it around 12.5 in the Northumberland refractor x105, DC s3 and
diameter around 1'. Nick James imaged the comet on
October
26 Observations with the Northumberland in March put the comet at
12 - 13th magnitude. Observing on April 9/10 I could barely see the comet
in the Northumberland, estimating it 13.6.
157 observations received so far give an uncorrected preliminary light
curve of 9.8 + 5 log d + 0.0151 abs(t-T-46.0)
Observations in ICQ format,
last observation 1999 May 12, updated 1999 August 12.
1998 U4 P/Spahr 1
was discovered by Timothy B Spahr of the University of Arizona on October
27.4 on CCD images taken with the Catalina Sky Survey 0.41-m f3 Schmidt.
It is 17th mag and was confirmed by Spacewatch Telescope images. [IAUC
7042, 1998 October 29]. The preliminary orbit is a distant elliptical one
and the comet will not become any brighter.
1998 U5 LINEAR
another object discovered by LINEAR has been identified as a comet. [IAUC 7044,
1998 October 31]. Preliminary orbit determinations suggest that it will brighten
a little further over the next few weeks. On 1998 November 1.18 I estimated
it at 12.3, rather brighter than 1998 U3. It is no longer visible.
125 observations received give an uncorrected preliminary light
curve of 7.8 + 5 log d + 19.6 log r
Observations in ICQ format,
last observation 1999 June 4, updated 1999 June 14.
1998 VS24 P/LINEAR
On further examining the Nov. 10-11 observations, published on MPS 3154, of an apparently unremarkable asteroidal discovery from the LINEAR program, G. V. Williams made identifications with isolated sets of observations from Visnjan on Oct. 24, 28 (the latter having been published on MPS 2894 as one of two objects that were both erroneously identified with 1998 UD19) and Nov. 26. The resulting orbit was very cometary in form, with a period of 9.6 years. Furthermore, he recognized that the object had made an extremely close approach (< 0.01 AU) to Jupiter in Oct. 1971, with additional approaches to 0.5-0.7 AU in both 1983 and 1995.
Following placement of the object in The NEO Confirmation Page, observations during Dec. 18.9-19.3 UT were reported by J. Ticha and M. Tichy (Klet), P. Pravec (Ondrejov), W. B. Offutt (Cloudcroft) and G. C. L. Aikman (Victoria), most of whom remark that the object indeed seems to be of cometary appearance. Offutt, using a 0.6-m f/7 Ritchey-Chretien, specifically notes: "Faint, somewhat asymmetrical coma extending about 6" north, 9" east, 14" south and 9" west of the central condensation, which is itself featureless, having a 'diameter' of approximately 5" (two to three times the extent of nearby star images having a similar peak intensity) and noticeable elongation in the north-south direction." Further details on the astrometry and orbit computation are given on MPEC 1998-Y17. [IAUC 7071, 1998 December 19]
1998 W1 P/Spahr 2
Timothy B Spahr of the University of Arizona discovered another comet on
November 16.4 on CCD images taken with the Catalina Sky Survey 0.41-m
f3 Schmidt. It is 16th mag and there is no visible tail, with the round
coma 18" in diameter. [IAUC 7052, 1998 November 17]. The preliminary orbit
suggests that it will reach perihelion in February and may brighten another
magnitude.
1998 W2 P/Hergenrother
C W Hergenrother found a comet on CCD images obtained
by Timothy B. Spahr on Nov. 22.10 in the course of the Catalina Sky Survey.
The comet was 17th magnitude and will fade. The comet was a short
period one, almost at perihelion. [IAUC 7057, 1998 November 23]
1998 W3 LINEAR
The LINEAR Team discovered an object that had unusual motion on
November 25.3 and placed the information in The
NEO Confirmation Page. On reporting astrometric follow-up, G. Hug,
Farpoint Observatory, Eskridge, KS, noted the object's appearance was
probably cometary, a point confirmed by other observers on request from
the Central Bureau and by the near-parabolic retrograde orbit, which shows
it to be a distant object that will get no brighter than its current 16th
mag. [IAUC 7063, 1998 November 28].
Observations in ICQ format, last observation
1999 March 13, updated 1999 August 12
1998 WG22 139P/Vaisala-Oterma
Precise positions of 1939 TN, an apparently asteroidal object
discovered by Y. Vaisala at Turku on 1939 Oct. 7 and observed by him and
L. Oterma on three more nights over a 35-day arc, were published in 1979
in Turku Obs. Report R10 and on MPC 4811. The orbit computation by
Oterma suggested to her that the object was a comet, and in a communication
to the Minor Planet Center in 1981 she remarked that a careful reexamination
of the plates suggested that the object was perhaps somewhat diffuse.
The introduction to the 1982 edition of the Catalogue of Cometary Orbits
quotes her conclusion that the object was probably a comet, but the
object was not actually listed as one. On MPEC 1998-X19, the object is
identified by S. Nakano, Sumoto, with 1998 WG22, a 19th mag apparently
asteroidal object observed by the LINEAR program on Nov. 18.26 and 21:
Fortuitously, this object was located only 4' from the result of
integrating forward from 1939 the orbital elements by Brian Marsden
on MPC 6815. Further LINEAR observations were made on Nov. 24.
On observing the object with the 1.8-m reflector at the Dominion
Astrophysical Observatory on Dec. 6.3 UT, D. Balam noted (in FWHM 3".1
seeing) an 8" coma and a tail extending 18" in p.a. 260 deg. On Dec. 7.1
W. Offutt, Cloudcroft, observing between clouds, also remarked on a
tail (or antitail) extending 17" in p.a. 257 deg, but no coma was noted.
M. Tichy, observing in poor conditions at Klet on Dec. 7.9, remarked
on a possible 6" coma.
The object's cometary nature seems now reasonably assured and it has a
period of 9.55 years [IAUC 7064, 1998 December 7].
1998 X1 P/ODAS
The Observatoire de la Cote d'Azur-Deutsches Zentrum fur Luft und
Raumfahrt Asteroid Survey (ODAS) discovered an 18th magnitude comet on
December 15.17 with the 0.90-m Caussols Schmidt camera. The orbit is
probably short period, but is currently rather indeterminate [IAUC 7067,
1998 December 17].
1998 X2 140P/Bowell-Skiff
G. V. Williams, Minor Planet Center, has rediscovered comet P/1983 C1 (= 1983c = 1983 II) in the course of his processing of two-night "asteroid" data obtained by the LINEAR program on Dec. 14 and 17. The indicated correction to the prediction on MPC 27081 (ephemeris on MPC 32547) was Delta T = +17.3 days. [IAUC 7076, 1998 December 28]
1998 Y1 D/LINEAR
LINEAR discovered
another faint comet, possibly of short period,
on December 22.31 [IAUC 7072, 1998 December 24]. It however was not
recovered and is presumed lost.
1998 Y2 P/Li
Weidong Li, Department of Astronomy, University of California at Berkeley, reports his discovery of a comet in the course of the Lick Observatory Supernova Search (cf. IAUC 6627; with the participation of M. Papenkova, E. Halderson, M. Modjaz, T. Shefler, J. Y. King, R. R. Treffers and A. V. Filippenko). The object was found automatically by the Katzman Automatic Imaging Telescope in the field of NGC 1041, but it was immediately recognized as a comet by Li, who then used the equipment to make a deliberate confirmatory observation, as well as follow-up observations on the following night. [IAUC 7075, 1998 December 28]. The comet is periodic with a period of about 15.2 years.
The Northumberland refractor
is the telescope that was used in the search for Neptune.
It now has a 0.30-m f18 doublet lens which gives a stellar limiting magnitude of around
15 at the zenith on good nights.
The Thorrowgood refractor was
built in 1864 and has a 0.20-m f14 doublet lens.
Published by Jonathan Shanklin. Jon Shanklin - jds@ast.cam.ac.uk
