An asteroidal object, already disocvered on Sep. 24, 2000, in the constellation Pisces, showed itself to be a comet at closer inspection. Comet C/2000 SV74 (LINEAR) was a 16.5m faint object with a diameter of 16" and a short tail of 20" at PA=150°. The comet reached perihelion at a distance of 3.5 A.U. in spring 2002(it was at a distance of 6 A.U. to the sun at discovery) (IAUC 7510). Merely nine visual observations by three members of the German comet section were received. Only the addition of 175 international reports made an analysis feasible. According to these the brightness evolution can be described most plausibly by the formula
m = 6.1m + 5×log D + 7.2×log r,
indicating a maximum brightness of 12.8m in mid-November 2001. The apparent coma diameter was estimated as 1.1' in July 2001, reaching a first maximum of 1.4' in September. Thereafter it decreased to 1.1' at the end of 2001, followed by a second increase (to 1.4' in May 2002), followed by a second decrease to 1.2' during fall 2002. It was measured as about 0.7' in March 2003. The absolute coma diameter was around 200.000 km at the beginning, decreasing to 180.000 km at the end of 2001. After a further increase to 240.000 km in May 2002 the diameter remained constant for several months. It had shrunk, however, to 120.000 km in March 2003. During the whole apparition the coma was only moderately condensed (until mid-2002 DC 3, thereafter DC 2).
Total Brightness and Coma diameter --------------------
On Aug. 26, 2002, the LINEAR team reported the discovery of two comets near the border of Ursa Minor / Draco, both in the same field (relative distance: 42') and moving in the same direction. Comet C/2002 Q2 (LINEAR) was reported as a object of magnitude 17.0, showing a 20", well-condensed coma, whereas 19.0m comet C/2002 Q3 (LINEAR) appeared very diffuse without condensation and coma diameter about 25". Astrometric observations quickly confirmed the apparent relationship of the two comets, with C/2002 Q2 as the primary component (IAUC 7960). They also indicated a rather small earth distance at discovery, meaning that this comets are very faint. CCD images of C/2002 Q3 on Sept. 4 and 5 taken with the 2.2-m reflector at Mauna Kea showed three separate fragments a few arcseconds apart; the brightest, component A (R = 21.7), appears elongated; component B was at R = 22.1 and component C at 22.6. Further observations allowed Z. Sekanina to improve his set of fragmentation parameters. The derived separation time of C/2002 Q3 from C/2002 Q2 is 1970.2 (+/-1.2 yr), when the parent comet was at a distance of 56 (+/-1) AU from the sun; the separation velocity was 0.18 (+/-0.01) m/s. A fragmentation sequence for the components of C/2002 Q3 itself has been determined. It is found that nucleus A, the original, eastern component, is the primary and that component D is different from B. It appears that C separated from A before 1980, a satisfactory solution indicating a fragmentation time in 1973 (+/- 4yr), at about 52 AU from the sun with a separation velocity of about 0.1 m/s. One cannot exclude the possibility that C separated directly from C/2002 Q2 about the time, or even before, component A did. The only satisfactory solution for D suggests that it broke off from A on 2002 July 5 +/-2 days (at about 1.5 AU from the sun) with a relative velocity of 1.3 m/s (IAUC 7978).
Visually the brightness of the comet was estimated as 12.5-13.0m during September 2002, with a coma of 1.5' diameter.
Later on Michael Jäger found out that both comets were captured on one of his photographs (of Comet Hönig) dated Aug. 20/21. However, both comets were so diffuse that he did not recognize them, all the more since he had to shorten the exposure time due to the bright moon. This result encouraged him to try to photograph the comets again on Sep. 2. The image shows both comets considerably brighter than predicted. He estimated C/2002 Q2 to be 13.8m, C/2002 Q3 at 14.2m, with coma diameters of 1.0' and 1.2, respectively, with the former more condensed than the latter. Michael Jäger expressed his surprise about published brightness estimates of 12m around that date, since the comet was clearly fainter than 92P/Sanguin which he photographed in the same night at an estimated magnitude of 12.5 - 13.0. Analysis of his photographs resulted in brightnesses/diameters of 13.6m/1.7' and 14.0m/1.2'.
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On Aug. 28, 2002, a comet of magnitude 17 was discovered on LINEAR images in the constellation Cygnus. Comet C/2002 Q5 (LINEAR) showed a 20" coma of magnitude 15.5 and a faint 1' tail in p.a. 140°. It will pass perihelion in November 2002, but will not experience significant brigthness variations during the next weeks (IAUC 7962). Michael Jäger photographed the comet on Sep. 12/13 at magnitude 13.3 (elliptical coma 1 x 1.5'). Michael Jäger photographed the comet again on Sep. 29 and 30 (8" Schmidt camera) as well as on Oct. 8 (10" Schmidt camera) as a 12.7m bright object with a 2' large coma. At that time visual observers estimated it to be of magnitude 13.5 with a coma of 1' diameter.
This comet surprised the - due to the low altitudes few - observers during winter 2002/03. After its conjunction with the sun it was estimated at the end of December to be of magnitude 12.5m hell - 1.5m brighter than expected. It seems to have reached maximum brightness (about 12.2m) in mid-January 2003. The diameter of the weakly condensed coma was reported at about 1.5'.
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On Oct. 25, 2002, the LINEAR project again discovered a new comet, this time near the border of the constellations Camelopardalis/Ursa Major. Comet C/2002 U2 (LINEAR) was of magnitude 15.5 and showed a 10" coma and a narrow tail at least 2' long in p.a. 280°. During winter 2002/03 it moved from Ursa Minor through Draco towards Hercules and was expected to reach magnitude 14 around the end ot this year, when it passed perihelion (IAUC 8000).
This comet seems to have faded rapidly after perihelion, because no additional visual observations have been published. In mid-January CCD-observers recorded a brightness of the 0.8' coma of about 15.5m Michael Jäger photographed the comet on the evening fo Nov. 23, 2002 with his 8" Schmidt-camera. He estimated it to be of magnitude 13.0-13.5m - 1m brighter than expected.
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A single(!) visual observation by a member of the German Comet Section was received of comet 46P/Wirtanen. In addition, only 35 international observations could be taken into account for the analysis. This numbers are surprising for a comet which reached a maximum brightness of 10.3m (beginning of August 2002), but is understandable since the comet was a morning object, was situated low above the horizon and showed a rather diffuse coma, resulting in a low-contrast object situated within the horizon haze. The brightness evolution can be described only with greater uncertainty since the variance in solar distance was extremely small during this apparition. A plausible solution is m = 9.0m + 5×log D + 7.5×log r. This is surprising since comet Wirtanen normally exhibits a great value for n. However, during November/December 2002 the brightness seems to have dropped dramatically because no visual estimate was reported thereafter - despite improving observing conditions. CCD-observers reported a brightness of 15m in December 2002 and of 17m in January 2003. The coma diameter was rather constant at 2.5' (200.000 km) during the period August - November 2002, the DC-value was constant at 3.
Total Brightness and Coma diameter --------------------
On Oct. 11, 2002, the NEAT team discovered a comet in the constellation of Aries, reporting its brightness to be 19m. Further observations of the comet - which got the preliminary designation P/2002 T4 (NEAT) - showed a 4" coma and a 20" long tail towards SSW. On the following day K. Muraoka pointed out, that this object is comet 54P/de Vico-Swift, last observed in 1965. It was observed at only three apparitions, in 1844, 1894 and 1965. The correction to the prediction was -7.5d. Calculations by B. Marsden show that the comet, now named 54P/de Vico-Swift-NEAT, passed Jupiter at a distance of only 0.16 AU on Oct. 18, 1968 (IAUC 7991/92). --------------------
A faint object reported as a possible NEO candidate and described as appearing cometary was recognized at the Minor Planet Center as being on the line of variation and to have the motion of comet 57P/du Toit-Neujmin-Delporte, but to be displaced from that brighter comet by more than 0.2°. NEAT had reported the brighter comet on July, but a check did not reveal anything obvious at the July 1 expected position of the new object. The object is described as diffuse and having a coma of diameter 12" and a delicate northeast-southwest elongation. The positions are fully consistent with the orbital elements for comet 57P with T for this "component B" delayed by 0.19 day. It should be noted that comet 57P was anomalously bright at its unfavorable 1996 return (T = 1996 Mar. 5.7) with 13.3m at the first postperihelic observation on July 24, some 5m brighter than expected (IAUC 7934). Observations with the 2.2m-reflector of the University of Hawaii showed additional 18 components (C-T) of comet 57P in observations taken on July 17 and 18. R-band magnitudes ranged from 20.0 to 23.5. The components ranged from well condensed to diffuse with little central condensation and had comae of diameter 1"-5". Components I, K, L, N, P, and T showed a lack of central condensation. The components are delayed with respect to T = 2002 July 31.181 TT for component A by the following times (in days): C, +0.012; D, +0.037; E, +0.053; F, +0.078; G, +0.156; H, +0.164; I, +0.170; J, +0.180; (B, +0.188); K, +0.194; L, +0.194; M, +0.224; N, +0.226; O, +0.240; P, +0.271; Q, +0.309; R, +0.311; S, +0.313; and T, +0.354 (IAUC 7935).
Z. Sekanina, Jet Propulsion Laboratory, made a preliminary analysis of the relative astrometry of the nuclei The results suggest that nucleus B could have broken off from primary A near perihelion in 1996. If the event had occurred exactly at perihelion, plausible values for the nongravitational deceleration require that B separated from A with a reasonably low velocity. Because of the comet's extremely low orbital inclination, it is doubtful that the separation parameters can ever be determined with high accuracy. All examined solutions yield essentially the same ephemeris, which shows that the projected separation of B from A will diminish in the coming weeks. It is unlikely that companions C-T are all products of the same event. In particular, C-F were probably released from A more recently than B was. Some of nuclei M-T may be fragments of B, but a more complex fragmentation hierarchy is also possible. Accurate astrometry on existing images and additional observations may allow one to make more, but not very, definite statements in the future. An excellent fit suggests that F separated from nucleus A most probably in the second half of May 2001, a little more than 400 days before perihelion at a heliocentric distance of about 3.6 AU (IAUC 7957).
International amateur observations showed component A to be of magnitude 13.5-14.0 during July/August 2002, with a coma of 0.7' diameter.
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Only few observations of comet 67P/Churyumov-Gerasimenko were published, thus its evolution during the current apparition remains unclear. A crude estimate of the brightness parameters is m0=9.5m / n=4. Based on two photographs made on Sep. 7 and 8 with his 10" Schmidt Camera Michael Jäger estimated the brightness of the comet to be 11.8m with a coma diameter of 1.5' and a tail of 3.5' length. Another photograph on Sep. 13 showed it to be of magnitude 12.0 with a coma diameter of 1.2' and a tail of 6' length (p.a. 298°). On a photograph of Oct. 5 the comet showed as a 12.5m object with a 0.75' coma and a 2.5' long tail pointing towards p.a. 283°. --------------------
Significantly brighter than predicted became comet 92P/Sanguin. For the analysis only one observation by a member of the German comet section and 25 international observations could be taken into account. The brightness evolution can be described by the formula m = 10.7m + 5×log D + 11.5×log r, resulting in a maximum brightness of 13.3m in mid-August. The coma diameter was around 0.8' (almost 30.000 km), the DC value at DC 3-4.
Total Brightness and Coma diameter
Michael Jäger estimated it on photographs, taken with his 10" Schmidt Camera on Sep. 3 and 13, to be 13.0m, with a coma diameter of 1.2'. On the photogrqph of Sep. 13 he could also identify a tail of 2' length in p.a. 340°.
Andreas Kammerer
