News - September 2007

2007 September 21

New Discovery!: Haibin Zhao (Purple Mountain Obs.") reports his discovery of a new comet on Sep. 17, 2007, with the 1.04-m f/1.8 Schmidt telescope at XuYi Station. After posting on the NEO Confirmation Page G. Sostero (Remanzacco, Italy), L. Buzzi and F. Luppi (Varese), E. Guido and Sostero (remotely from Mayhill) and R. Ligustri (Talmassons) were able to confirm the cometary nature of the 18^m object. The first orbit for comet P/2007 S1 (Zhao), including pre-discovery observations by LONEOS from Sep. 8, and 15, 2007, indicates perihelion on Dec. 10, 2007, at about 2.5 AU. The period is about 7.5 years. (IAUC 8873, subscription required, MPEC 2007-S36)

2007 September 19

IAUC 8871 and 8872 offcially announce and confirm the identity of the SOHO comet found by Bo Zhou on Sep. 10, 2007, with comets 1999 R1 and 2003 R5, as predicted by Sebastian F. Hönig in 2005 and published in Astronomy and Astrophysics 445, 759 (2006). The linked orbit by B. G. Marsden for comet P/2007 R5 (SOHO), based on only the C2 observations (with re-measured ones of the 1999 and 2003 apparitions) indicate a perihelion date of Sep. 11.32, compared to the prediction by Hönig of Sep. 11.26, which was only about 1.5 hours too early! M. Knight (University of Maryland), who has analysed the brightness behaviour of this comet at all three apparitions remarks that the lightcurves are more typical for a comet with several brightness peaks. The evolution at all three apparitions is remarkably similar. It should also be noted that the comet has not yet been detected in STEREO imagery, which is typical for comets, where only bright ones are seen while minor planets can be detected to a much fainter magnitude. The overall count of SOHO comets will be reduced by one. (IAUC 8871, subscription required, IAUC 8872, subscription required, MPEC 2007-S16)

2007 September 17

New Discovery!: A. R. Gibbs reports his discovery of another new comet on Sep. 14, 2007, in the course of the Mt. Lemmon Survey. After posting on the NEO Confirmation Page G. Hug (Scranton), J. G. Ries (McDonald Observatory), V. Gonano, E. Guido, and G. Sostero (Remanzacco) and P. Birtwhistle (Great Shefford) were able to confirm the cometary nature of the 18^m object. The first and preliminary orbit for comet P/2007 R3 (Gibbs) shows the comet to have passed perihelion already on Jun. 6, 2007, at about 2.2 AU. The period is about 10.4 years. This is the 13^th comet for the Mt. Lemmon Survey and the 7^th for Gibbs. (IAUC 8869, subscription required, MPEC 2007-S02)
New Discovery!: G. J. Garradd reports his discovery of a new comet on Sep. 14, 2007, in the course of the Siding Spring Survey. After posting on the NEO Confirmation A. C. Gilmore and P. M. Kilmartin (Mt. John Obs.) were able to confirm the cometary nature of the 18^m object. Pre-discovery images from Siding Spring of Aug. 12, 2007, were also found. The first orbit for comet P/2007 R4 (Garradd) shows perihelion on Sep. 26, 2007, at about 1.9 AU. The period is about 14.3 years. This is the 41^st comet for the Siding Spring Survey and the 7^th for Garradd. (IAUC 8870, subscription required, MPEC 2007-S04)

2007 September 12

New Discovery!: A. R. Gibbs reports his discovery of a new comet on Sep. 10, 2007, in the course of the Catalina Sky Survey. After posting on the NEO Confirmation Page J. W. Young (Table Mountain), J. E. McGaha (Tucson) and P. Birtwhistle (Great Shefford) were able to confirm the cometary nature of the 18^m object. The first and preliminary orbit for comet P/2007 R2 (Gibbs) shows perihelion on Aug. 26, 2007, at about 1.5 AU. The period is about 6.0 years. This is the 49^th comet for the Catalina Sky Survey and the 6^th for Gibbs. (IAUC 8868, subscription required, MPEC 2007-R55)

2007 September 11

A non-Kreutz comet discovered on Sep. 10, 2007, in C2 images of the SOHO/LASCO coronagraph is most likely identical with comets C/1999 R1 and C/2003 R3 as predicted by Sebastian F. Hönig (Bonn, Germany). In 2005, Hönig linked the 1999 and 2003 comets and predicted the next perihelion to occur on Sep. 11.26, 2007. The comet found by Bo Zhou is expected to pass perihelion within a few hours of this prediction. If confirmed this comet will be the first safe periodic SOHO comet and the periodic comet with the smallest perihelion distance (0.054 AU). The comet will most likely be numbered in the near future and it has been suggested by several people that it should be renamed for Hönig. (Comets Mailing List, SOHO comet hunter Mailing List)

2007 September 9

New Discovery!: S. Larson (LPL) reports his discovery of a new comet on Sep. 4, 2007, in the course of the Mt. Lemmon Survey, which was confirmed by R. A. Kowalski (Mt. Lemmon) four days later. After posting the object on the NEO Confirmation Page G. Hug (Eskridge), L. Buzzi and F. Luppi (Varese), G. Sostero, E. Guido, and V. Gonano (Remanzacco), C. Jacques and E. Pimentel (Belo Horizonte), E. Reina L. (Masquefa) and J. Young (Table Mountain) also confirmed the cometary appearance of the 18^m object. The first and very preliminary orbit for comet P/2007 R1 (Larson) indicates perihelion on Feb. 22, 2009, at about 3.8 AU. This is the 12^th comet for the Mt. Lemmon Survey. (IAUC 8867, subscription required, MPEC 2007-R36)

2007 September 2

Syuichi Nakano (Sumoto, Japan) reports his identification of comet P/2007 N1 (McNaught) with an object observed by NEAT on Aug. 5, and Nov. 11, 2000, and by LONEOS on Aug. 21, 2000. P/2000 P3 = P/2007 N1 (McNaught) passed perihelion on Jan. 12, 2001, at this last apparition. I and independently Reinder Bouma, were able to find and report additional NEAT images of Sep. 3, and Dec. 12, 2000, showing the comet clearly diffuse and with a short tail. (MPEC 2007-R04)