On June 3, 2005 R.H. McNaught discovered a third comet within two days in the course of the Siding Spring Survey. Comet C/2005 L3 (McNaught), situated in the western part of the constellation Piscis Austrinus, showed a condensed 10" coma of magnitude 18.0. According to the first elements it will pass its rather distant perihelion at the end of 2007 (IAUC 8536). During the years 2007 and 2008 it could become as bright as 15.0 mag, thereby moving through Ophiuchus and Hercules. Visual observations showed the comet as an object of magnitude 13.5 in July 2007, displaying a 0.7' coma. In spring 2008 it was estimated at magnitude 13.0 and showed a medium-condensed 0.8' coma. At the end of 2008 it was estimated as about 14.5 mag. All brightness estimates can be described rather well by the parameters m0=4.0 mag / n=3, yielding a maximum brightness of 13.1 mag in summer 2007 and 2008.
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On images taken in the course of the Catalina Sky Survey R.E. Hill discovered a comet in the constellation Pisces (near Pegasus) on Sep. 28, 2006. Comet C/2006 S5 (Hill) was of magnitude 18.5, showing a 10" tail pointing towards southwest. It will pass perihelion in December 2007, expected to brighten to 13 mag by then (IAUC 8755). Between fall 2007 and spring 2008 it would be brighter than 14 mag, thereby moving through Gemini. It rounds the sun with a period of about 1000 years (MPEC 2006-V22). According to the few published observations the comet reached its maximum of 13.5 mag at the end of 2007, with the medium condensed coma short of 1'.
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An apparently asteroidal object, already discovered on Nov. 20, 2006 at Mt.Lemmon Observatory near the border of the constellations Taurus/Aries showed cometary morphology on Apr. 30, 2007. Comet C/2006 WD4 (Lemmon) presented a spiral-like 20" coma. An observation on May 2 showed an elliptical coma (12x18"), with the major axis in p.a. 235°. The total magnitude was measured as 14.2 mag, the brightness of the central condensation as 15.4 mag (IAUC 8835). The comet passed the sun and earth at rather small distances (q=0.6 AU, delta=0.26 AU). Due to its very faint absolute magnitude it did not became brighter than 12 mag. Because it was near the sun for most of the time it could only briefly be glimpsed above the evening western horizon during the last days of May.
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On Jan. 23, 2007 B.A. Skiff discovered an 18 mag comet on LONEOS images near the border of the constellations Ursa Major / Leo Minor. Comet C/2007 B2 (Skiff) showed a highly condensed 10" coma without a tail. It will pass perihelion in fall 2008, expected to reach 13 mag (IAUC 8799 / MPEC 2007-C36). It will be brighter than 14 mag between January 2008 (positioned in the northern part of Virgo) and the end of 2009. Due to its southeastern movement it will disappear for mid-European observers already in June 2008 (positioned near the borders of Virgo/Leo/Cancer), at about the time of maximum brightness. The observations published until June 2008 (with considerable scatter) show the comet to be nearly as bright as expected. In March 2008 it was of magnitude 13 and showed a well-condensed coma with a diameter short of 1' coma.
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An asteroidal object of magnitude 18.5, discovered on Apr. 10, 2007 by the LINEAR-project near the border of the constellations Hercules/Lyra showed cometary morphology by closer inspection. Comet C/2007 G1 (LINEAR) showed a 10" coma of magnitude 17.8, which was elongated in p.a. 260°. The comet will pass perihelion in November 2008 and could reach 12 mag during summer 2008 (IAUC 8828 / MPEC 2007-H07). It should become brighter than 15 mag - then positioned in Ophiuchus - near the end of 2007. It will move towards Lupus until the end of July 2008, where it will disappear for mid-European observers. The number of published observations of this comet is too small for any reasonable analysis. The estimates seem to confirm the proposed brightness parameters m0=5.5m/n=4. The maximum brightness of 11.5 mag was reached in summer 2008, with a coma of about 2-3'.
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On Apr. 17, 2007 R.H. McNaught discovered a 16.0 mag comet near the border of the constellations Capricornus/Aquarius on CCDs taken in the course of the Siding Spring Survey. Comet P/2007 H1 (McNaught) showed a 12" coma and a 25" tail in p.a. 250°. Additional observations showed a 20" coma and a 2.2' tail. This comet orbits the sun with a period of 7.2 years and will pass perihelion in mid-August 2007. Then situated in the region Aquarius/Pisces/Cetus it could reach 14 mag (IAUC 8830 / MPEC 2007-L25). In September/October 2007 it was of magnitude 13.0, displaying a medium-condensed coma of diameter short of 1'. During winter 2007/08 it will be positioned in Cetus, thus being an evening object, which slowly fades.
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An apparently asteroidal object of magnitude 19.0 discovered in Sextant in the course of the Siding Spring Survey on May 23, 2007 by G. Garradd showed cometary morphology by closer inspection. Observations by R.H. McNaught showed a diffuse 6" coma. Comet C/2007 K3 (Siding Spring) will pass perihelion in spring 2008 and could reach 14 mag in summer 2008 in the region Aquarius/Pegasus (IAUC 8839).
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Walter Kutschera succeeded in photographing comet 50P/Arend on Aug. 17/18, 2007 with a Watec-camera and his 54cm-reflector. It showed a moderately condensed (DC 3) 1.2' coma of magnitude 14.5. Additional observations with the same equipment: Oct. 12/13: 14.7 mag / 0.9' coma, Oct. 31/Nov. 1: 15.0 mag / 0.8' coma.
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For the analysis of the apparition 2007 of comet 93P/Lovas 10 observations of 2 members of the German Comet Section and 35 international observations could be used. They indicate a brightness evolution according to the formula m = 8.8 mag + 5×log D + 17.5×log r, yielding a maximum brightness of 12.6 mag in mid-November 2007. The coma diameter increased from 0.5' (20.000 km) to a maximum of 1.1' (50.000 km) at the start of December, thereafter decreasing to 0.8' (40.000 km) at the start of January. At first the coma was moderately condensed (DC 4-5), but got more and more diffuse thereafter (start of December: DC 3-4, start of January: DC 2-3).
Total Brightness and Coma Diameter
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Near the end of 2007 observers reported the possible splitting of the nucleus of comet 110P/Hartley, which however, could not be confirmed. The comet got significantly brighter than expected. At the end of the year 2007 it was of magnitude 14.5, which was kept at least until the beginning of March 2008. The coma diameter measured about 0.5'.
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Since Dec. 2002 comet 133P/Elst-Pizarro had not shown any cometary activity. However, observations with the 2.2m-University of Hawaii telescope on June 11, 2007 (6 weeks prior to the perihelion passage) shows the object to display a linear 20" tail in p.a. 256°. The brightness was estimated as R=19.5 mag. This observations confirms, that this object is an ice-covered asteroid or a Main-Belt-comet, which is only active near the perihelion of its orbit (IAUC 8847).
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On Oct. 12, 2007 R.H. McNaught recovered comet Shoemaker-Levy 1 (1990o) in the constellation Telescopium. Comet P/2007 T3 (Shoemaker-Levy) showed a 10" coma of magnitude 18.0 and a positional displacement according to dT=+4.5 days! It passed perihelion in mid-December, not expected to get brighter than 17 mag. It was given the permanent designation 192P/Shoemaker-Levy (IAUC 8879/88). The few published observations indicate a brightness of 13.5 mag in January 2008! This could indicate either an extremely high activity parameter or (more probable) an outburst or a rather asymmetric brightness evolution of this comet.
Andreas Kammerer
