end of the month. It crosses from the evening to the morning sky through October and will sink into the morning twilight by mid November, when it could be 6th magnitude. This magnitude may however be optimistic as observations from the SOHO spacecraft in 2000 showed that it suddenly brightened after perihelion, by which time it will be at a poor elongation. A possible explanation for this behaviour is that Encke has two active regions, an old one with declining activity, which operates prior to perihelion and a recently activated one present after perihelion. There is, however, little evidence for a secular fading in the archive of BAA observations of the comet. The comet is the progenitor of the Taurid meteor complex and may be associated with several Apollo asteroids.

2012 K5 (LINEAR) is at perihelion in 2012 November, and then passes 0.3 AU from the Earth at the end of 2012 December. It is well placed for Northern Hemisphere observation and is circumpolar around the time of closest approach when it may reach 7th magnitude, though the magnitude is very uncertain. It passes some 4° from M37 around 2013 January 3/4, but it then fades rapidly, though should still be in visual range all month.

The other periodic and parabolic comets that are at perihelion during 2013 are unlikely to become brighter than 12th magnitude or are poorly placed. Ephemerides for these can be found on the CBAT WWW pages. One D/ comet has predictions for a return, though searches at favourable returns in the intervening period have failed to reveal the comet and its orbit has been perturbed by Jupiter to give a larger perihelion distance. There is however always a chance that it will be rediscovered accidentally by one of the Sky Survey patrols. Several SOHO comets are predicted to return, however these will only be visible from the SOHO or STEREO satellites.

Looking ahead to 2014, the prospects for periodic comets are even worse, with the most interesting object being 2004 CB, which could reach 11th magnitude when it passes 0.05 AU from the earth in May. 2012 K1 (PanSTARRS) may reach 6th magnitude after its August perihelion, but is unfortunately a morning object.

References and sources

Minor Planet Circulars

Nakano Notes at http://www.oaa.gr.jp/~oaacs/nk/

Theories on the structure of comets suggest that any comet could fragment at any time,

so it is worth keeping an eye on some of the fainter periodic comets, which are often

ignored. They would make useful targets for CCD observers, especially those with time

on instruments such as the Faulkes telescope. In addition to those in the BAA

Handbook, ephemerides for new and currently observable comets are published in the

Circulars, and on the Section, CBAT and Seiichi Yoshida's web pages. Complete

ephemerides and magnitude parameters for all comets predicted to be brighter than

subscription to the ICQ are available on the Internet. A section booklet on comet

observing is available from the BAA Office.

29P/Schwassmann-Wachmann is an annual comet that has outbursts, which over the

last decade seem to have become more frequent. The comet had one of its strongest

outbursts yet recorded in early 2010. The comet is an ideal target for those equipped

with CCDs and it should be observed at every opportunity. The comet begins the year

in Corvus, less than a degree from M104, and completes its retrograde loop in nearby

Virgo by mid summer. It crosses back into Corvus, before ending the year in Virgo.

The comet is at opposition at the end of March and passes through solar conjunction in

mid October.

78P/Gehrels reaches perihelion in January, but its distance from the Earth is already

increasing, and so it is fading from its best in the autumn of 2011. It is however

relatively well placed in the evening sky, and so a suitable target for telescopic

observation.

solar monitoring satellites that will see it around perihelion. Southern Hemisphere

observers may get to see it as a relatively poorly placed telescopic object in the morning

sky prior to perihelion, and in the evening sky post perihelion.

will be a morning object when at its best in early August.

1994 X1 (P/McNaught-Russell) makes its first return to perihelion this year. Although

not observed visually at the discovery apparition, its brightness on the Schmidt plates

suggests that it might have been within range and the predictions are based on this

assumption. It may become visible in July, and will be at its brightest in November and

December, when it is well placed in the evening sky.

Observing near Saturn with his 0.41-m reflector he noted a diffuse object of magnitude

10.5. The cometary nature of the object was confirmed by Peter Birtwhistle and Richard

Miles amongst others. The Japanese comet hunter Shigheki Murakami made an

independent discovery of the comet on 2006 October 4, but by this time the object had

been placed on the NEOCP and an IAUC issued. This is a very good return, as the

comet passes 0.19 AU from the Earth, which gives it the potential to become a

binocular object, if it behaves as it did at the discovery return. It is a little surprising

that the comet hadn’t been discovered previously, for example the 1991 return was

relatively favourable, and so it may have been caught in outburst. It had not been

recovered by 2011 October, which strengthens this hypothesis. It is well placed in the

evening sky when at its brightest, but is rapidly moving south, so that UK observers will

lose it by mid February. There is the possibility of a meteor shower from the comet

with maximum on New Year’s Eve.

2009 P1 (Garradd) currently holds the best prospect for UK observers. It begins the

placed in the morning due to its location in Hercules. It is moving north, and passes less

than 20’ from globular cluster M92 on February 3, soon becoming visible all night. It is

furthest north on March 12, at just over 70° declination, but is fading and by the end of

of May, by which time it will have crossed half the sky to Cancer.

southern hemisphere object. Circumpolar and lying below the pole, it will be visible in

the evening sky, which may encourage some observers to turn their telescopes towards

it.

The other periodic and parabolic comets that are at perihelion during 2012 are unlikely

be found on the CBAT WWW pages. Several D/ comets have predictions for return,

though searches at favourable returns in the intervening period have failed to reveal the

comets and it is possible that they are no longer active. There is however always a

chance that they will be rediscovered accidentally by one of the Sky Survey patrols.

could provide one of the brighter comets of the decade after its March perihelion.

mag

P/Spacewatch (2005 JN) Jan 6.1 2.29 6.56 1 14.0 10.0 19

131P/Mueller Jan 7.4 2.42 7.07 3 13.0 10.0 17

P/Gibbs (2011 C2) Jan 9.5 5.39 20.0 0 9.0 10.0 19

P/Levy (2006 T1) Jan 12.3 1.01 5.28 1 10.5 10.0 7

78P/Gehrels Jan 12.9 2.01 7.23 5 3.5 20.0 10

P/McNaught (2005 J1) Jan 15.8 1.54 6.75 1 16.5 10.0 20

McNaught (2011 Q2) Jan 19.8 1.35 10.0 10.0 13

244P/Scotti Jan 20.3 3.92 10.8 2 9.0 10.0 17

5D/Brorsen Feb 5.3 0.53 5.61 5

D/Brooks (1886 K1) Feb 6.3 1.89 6.69 1

Gibbs (2010 M1) Feb 7.8 2.30 9.0 10.0 15

21P/Giacobini-Zinner Feb 11.8 1.03 6.60 14 7.8 17.7 11

198P/ODAS Feb 15.8 2.00 6.82 2 10.5 15.0 16

105P/Singer Brewster Feb 26.2 2.05 6.47 4 12.5 15.0 18

3D/Biela-A Feb 27.0 0.80 6.59 6

182P/LONEOS Mar 5.4 1.01 5.10 2 18.0 10.0 17

P/Novochonok-Gerke (2011 R3) Apr 3.3 3.56 10.7 0 11.0 10.0 19

242P/Spahr Apr 3.5 3.98 13.0 2 8.0 10.0 17

58P/Jackson-Neujmin Apr 10.0 1.37 8.22 6 11.0 15.0 18

163P/NEAT Apr 12.8 2.06 7.30 3 14.5 10.0 19

LONEOS (2006 S3) Apr 16.5 5.13 2.0 10.0 12

D/Denning (1894 F1) Apr 16.8 1.36 8.11 1

171P/Spahr Apr 30.6 1.76 6.70 2 10.2 15.0 16

60P/Tsuchinshan May 13.5 1.62 6.56 7 10.5 15.0 15

LINEAR (2010 R1) May 18.9 5.62 6.0 10.0 17

P/Gibbs (2006 Y2) May 20.8 1.26 5.35 1 18.0 10.0 20

P/ASH (2011 N1) May 31.1 2.86 15.8 0 11.5 10.0 18

P/LINEAR (2003 O2) Jun 10.7 1.50 8.75 1 14.5 10.0 18

138P/Shoemaker-Levy Jun 11.7 1.70 6.90 3 15.0 10.0 19

P/Pan-STARRS (2011 U1) Jun 29.2 2.23 8.76 0 14.5 10.0 20

152P/Helin-Lawrence Jul 9.2 3.12 9.54 2 10.0 10.0 18

96P/Machholz Jul 14.8 0.12 5.28 5 13.0 12.0 2

189P/NEAT Jul 20.4 1.18 4.99 2 19.0 10.0 16

185P/Petriew Aug 13.5 0.93 5.46 2 11.0 10.0 11

LINEAR (2011 O1) Aug 18.5 3.89 7.0 10.0 15

P/LONEOS (2006 Q2) Aug 22.0 1.34 5.96 1 19.5 10.0 19

P/McNaught (2005 K3) Sep 12.7 1.50 7.02 1 13.5 10.0 14

160P/LINEAR Sep 18.5 2.07 7.90 2 15.0 5.0 17

158P/Kowal-LINEAR Sep 27.5 4.58 10.3 2 9.0 10.0 18

P/Larson (2005 N3) Sep 29.4 2.19 6.78 1 14.0 10.0 18

168P/Hergenrother Oct 1.7 1.41 6.89 2 15.5 10.0 15

P/Christensen (2005 T2) Oct 7.1 2.21 7.47 1 14.5 10.0 19

Bressi (2011 U2) Oct 9.2 2.49 10.0 10.0 16

3D/Biela-B Oct 9.9 0.83 6.74 6

McNaught (2011 R1) Oct 19.7 2.08 6.5 10.0 11

P/McNaught-Russell (1994 X1) Dec 4.5 1.28 18.3 1 10.0 10.0 11

P/Spacewatch (2006 F4) Dec 14.1 2.34 6.63 1 15.0 10.0 21

P/Hermann (1999 D1) Dec 18.4 1.64 13.8 1 15.0 10.0 18

The date of perihelion (T), perihelion distance (q), period (P), the number of previously

(which must be regarded as uncertain) are given for each comet. The magnitudes,

orbits, and in particular the time of perihelion of the D/ comets, are uncertain.

References and sources

Period Comets, Bratislava (1986).

and http://www.cometography.com.

MPC/CBAT, (2008).

Minor Planet Circulars

Nakano Notes at http://www.oaa.gr.jp/~oaacs/nk/

Jonathan Shanklin