Comets, quasi-comets and the Comet Section. Jonathan Shanklin Director, BAA Comet Section

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1 Comets, quasi-comets and the Comet Section Jonathan Shanklin Director, BAA Comet Section

2 BAA founded 1890 Comet Section formed 1891 Around 40,000 observations Virtually all extant observations are post WW2 Visual observations of nearly 500 different comets, including returns of over 100 periodic comets, over 60 years

3 Jonathan Shanklin, 12 th Director

4 Comet Section Publications Comet Section web page at Yearly Comet Section newsletter (available on the internet) Papers in Journal of the British Astronomical Association Reports on the comets of each calendar year (includes magnitude parameters) Predictions on comets for the coming year Predictions in the BAA Handbook BAA Observing Guide to Comets New edition in preparation

5 Comets

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7 Amateur visual observations of 67P 1. The comet was discovered in 1969 following a very close encounter with Jupiter (0.05 AU) in 1959 that reduced the perihelion distance from 2.7 AU to 1.3 AU. 2. There were no visual observations at the discovery return and the photographic magnitudes are a little inconsistent. 3. The comet was poorly placed in 1976; when within visual range it was at a small elongation from the Sun 4. There was a well observed return in 1982 when the comet had a perihelic opposition 5. The comet was again poorly placed in There have been observations at the last three returns.

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12 Amateur visual observations of 67P 1. The comet is intrinsically brightest about 40 days after perihelion 2. The comet may show a secular brightening or it may change its absolute magnitude from return to return 3. There is little evidence for significant outbursts

13 Amateur visual observations of 67P If the perihelion distance is the critical factor in the absolute magnitude: The comet should become a binocular object in 2015 The activity of the comet will be similar to that of 2009 The observing circumstances will be similar to those of 2002, when the comet was a morning object. At 1.21 AU the perihelion distance in 2021 is the closest for the next 100 years and the comet will be at opposition when near perihelion. If my prediction for 2015 is correct the comet may reach naked eye visibility in 2021.

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16 Solar halo over the new Halley station, Antarctica

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18 Comet 2011 W3 (Lovejoy), Australia, 2011 December 24

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28 Quasi-comets

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33 Image of 2010 G2 by Nick James, showing its slightly non-stellar profile

34 2012 BJ 98 (Lemmon) An object reported as asteroidal in images obtained in the second half of January, was identified as cometary in images taken by the Mt Lemmon Survey on March 1, and then linked to images obtained by the Steward Observatory, Pan-STARRS and the Catalina Sky Survey. The comet has perihelion at 2.2 AU in September and has a period of around 70 years CH 17 (MOSS) The Morocco Oukaimeden Sky Survey (MOSS) discovered this comet on February 7.12, though it had earlier been flagged as an asteroid. It is due to reach perihelion at 1.3 AU in September. It could reach 13th magnitude, but is not well placed for observation from the UK NJ (P/La Sagra) The La Sagra team reported an asteroid found on images taken on July 13.03, and their positions combined with those from several other observatories lead to the automatic determination of an orbit, which had a high inclination and a period of around 50 years. This was published on July 14. Further observations and indications that the object had a tail lead Gareth Williams to compute a manual orbit for the comet, which was published on July 18. The comet was around a month past perihelion at 1.3 AU and the period is around 25 years.

35 A/2012 DG 61 [PanSTARRS] This unusual asteroid was discovered by the Pan-STARRS 1 1.8m Ritchey-Chretien reflector on February [MPEC 2012-E10, 2012 March 1, 3-day orbit]. It has an orbit with a period of around 5.2 years and perihelion is at 0.8 AU in 2012 July. It can approach Jupiter within 0.25 AU and the Earth to 0.16 AU. The orbit has a Tisserand criterion of 2.75 with respect to Jupiter. A/2012 GS 5 [PanSTARRS] This unusual asteroid was discovered by the Pan-STARRS 1 1.8m Ritchey-Chretien reflector on April [MPEC 2012-G46, 2012 April 14, 3-day orbit]. It has an orbit with a period of around 6.2 years and perihelion is at 0.5 AU in 2012 June. It can approach Jupiter within 0.5 AU and the Earth to 0.29 AU. The orbit has a Tisserand criterion of 2.35 with respect to Jupiter. A/2012 HD 2 [Spacewatch] This unusual asteroid was discovered at the Steward Observatory, Kitt Peak by Jim Scotti with the 0.9m Spacewatch reflector on April It has a period of around 28 years and perihelion is at 2.5 AU in 2012 September. It has a retrograde orbit, with aphelion at 16 AU. [MPEC 2012-H32, 2012 April 20, 2-day orbit]. The orbit has a Tisserand criterion of with respect to Jupiter.

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