On May 21, 2004 the Catalina project reported the discovery of an asteroidal object near the border of the constellations Aquarius/Aquila, which showed marginally cometary appearance. Comet C/2004 K1 (Catalina) was of magnitude 17.5 and slightly more diffuse than the stars nearby. It will pass perihelion in summer 2005 (IAUC 8343). During summer 2005 it could become observable as an object of magnitude 14-15 in the region Ophiuchus/Bootes. CCD-observations during spring 2005 showed an object of about magnitude 15.0 with a 1' coma.
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An apparently asteroidal object of magnitude 17.5, discovered on Oct. 19, 2004 by the LINEAR-team in the constellation Cancer, had been found to show a faint 9" coma and a broad 12" tail in p.a. 320°. Comet C/2004 U1 (LINEAR) reached perihelion at the beginning of December 2004, expected to get not more than one magnitude brighter (IAUC 8421).
However, Ramon Naves (Spain) and Ken-ichi Kadota (Japan) noticed an outburst of 3 magnitudes. On Nov. 22, 2004 of magnitude 17 it had brightened to 14 mag on Nov. 27 (Comet Mailing List). The comet was observed visually between the beginning of December 2004 and mid-January 2005. According to the small number of published observations it showed a constant brightness of 13.0-13.2 mag during this period, implying brightness parameters of about m0=7.5m / n=4. In mid-January the observations ended abruptly. Although the comet was expected to fade during those days, the fading should have been rather slow, applying the above mentioned brightness parameters. Thus it is possible that the comet experienced a sudden drop in brightness.
J. Young detected a 20.0 mag well-defined secondary component in the tail-direction on CCD-images taken on Oct. 21/22, 2005. The main component was of magnitude 18.5 at that date (IAUC 8624).
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On Nov. 30, 2004 M. Mattiazzo reported the discovery of a faint object in the SWAN data. Between Nov. 9 and 25 the brightening object moved from Corvus through the southern regions of Virgo towards the direction of Libra. However, the derived positions showed an uncertainty of about 1°. M. Mattiazzo pointed out, that this object, if real, could become visible for SOHO. On Dec. 16 J. Sachs reported the discovery of a comet with tail via the SOHO data, which turned out to be the SWAN object. The brightness of comet C/2004 V13 (SWAN) increased from 6.5 mag to 6.1 mag between Dec. 16.26 UT und 16.74 UT. It passed perihelion at the small solar distance of only 0.18 AU on Dec. 21 (IAUC 8455/56).During the preceding days it was speculated if it could survive the close proximity to the Sun since the calculated absolute brightness of about 12.0 mag was below the Bortle-Limit. Well, it did, but barely. It was clear that earth-bound observations would be difficult as the quickly fading comet would remain at low altitudes.
The first earthbound observation was achieved by Ken-ichi Kadota (Japan) on Dec. 26. On a CCD image the comet presented itself as a 10.1 mag object - several magnitudes fainter than expected. David Seargent (Australia) succeeded in visually observing the comet from a dark site with his 25 cm (10") reflector on Jan. 5, 6 and 7, estimating it to be 11.7 mag. A Swan-Band filter enhanced the contrast on the first day, but the enhancement grew more and more subtle on the following nights (Comet's Mailing List). The few published observations can be described quite well with the parameters m0=13.8m / n=3.2. The coma diameter was estimated to be around 1.5'. Due to the unfavourable circumstances these results are uncertain, of course.
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An apparently asteroidal object of magnitude 17.0, discovered by the LINEAR-team on Nov. 3, 2004 in the constellation Taurus, showed cometary activity at closer inspection. On Nov. 11 comet P/2004 VR8 (LONEOS) displayed a 10" coma and a 16" tail in p.a. 140°. It will reach perihelion in fall 2005 and may reach magnitude 16.0 at the end of 2005. It orbits the sun with a period of 10.7 years (IAUC 8451).
CCD observations in Dec. 2005 and Jan. 2006 showed the comet at magnitude 15.5-16.0. This was in accordance with the first visual observation at the end of January, giving the magnitude as 14.8. At the end of March the 0.5' coma was estimated visually at magnitude 14.0 mag - 2 mag brighter than expected.
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Comet 40P/Väisälä (U=10.8 years) should become accessible with amateur equipment during winter 2003/04. This will be the seventh apparition since its discovery in 1939. During these months it will move from Virgo to Libra, being a morning object. According to the ICQ handbook it shows a high activity factor n, resulting in a predicted brightness increase from 15.5 mag to 14.0 mag, although the variance in r will be small. Until April 2004 only a small number of CCD-observations have been published, although the comet should have been within the range of visual observers. According to these the comet peaked at magnitue 13.5-14.0. The weakly condensed coma displayed a diameter of about 1'.
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Significantly brighter than expected became Comet 62P/Tsuchinshan, as is shown by 10 observations by 2 members of the German Comet Section and 35 international ones. The estimates can be moderately well described by the formula m = 8.5m + 5×log D + 20×log r, resulting in a maximum brightness of 11.9 mag around New Year 2004/05. During the apparition the coma diameter decreased continuously from 2.2' (100.000 km) to 1.6' (60.000 km) at the beginning of April 2005. The degree of condensation remained constant at DC 2-3.
Total Brightness and Coma Diameter
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Michael Jäger and Gerald Rhemann observed comet 118P/Shoemaker-Levy on the morning of Feb. 17 with an 8"-Schmidtcamera and CCD as a 15m object, displaying a very faint tail. According to Akimasa Nakamura and Mitsunori Tsumura the comet brightened from 16.5m to 14.5m between mid-February and mid-March 2004 (Comets Mailing List). Thus in February it was 1m and in March 2m brighter than expected. The comet reached magnitude 14.5-15.0 in March 2004, showing a coma diameter of about 0.8'. Since then the brightness fades slowly.
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Comet 123P/West-Hartley will pass perihelion for the third time since discovery. According to the ICQ-handbook it should reach magnitude 13.5 at the beginning of 2004. The few CCD-observations published so far do not allow to define the brightness behaviour with any certainty, but are in agreement with the predictions. Thus the comet should be observable with amateur equipment (magnitude about 13.5) as it moves through the constellation Virgo. According to the published estimates the brightness evolution followed the predictions. The comet peaked at magnitude 13.0-13.5, showing a coma diameter of about 0.7'. Until end of May the comet faded to magnitude 14.5.
Andreas Kammerer
