Copyright©1997 by Gordon Garradd (Australia) This photo of periodic comet Encke was obtained by G. Garradd on 1997 June 5. It was a 100-second exposure obtained with a 25-cm Newtonian and a CCD camera. The comet was then slightly more than two degrees above the horizon. A thin gas tail can be seen. The field of view of the image measures 8 arcmin high and 19 arcmin wide. The colouring does not represent the comet’s true colour, but was used to enhance some of the faint features.
2003 sees Comet 2P/Encke’s 59th observed return to perihelion since its discovery by Mechain in 1786. The comet was “discovered” again in 1795, 1805, and 1818, and during the last of these returns Encke himself observed it. His calculation of the comet’s orbit led him to recognise that it was the very same object already seen in 1786, 1795, and 1805. Encke went on to predict that it would reappear 3.3 years hence, in 1822, and on June 2nd of that year Charles Rümker at Parramatta in New South Wales, Australia, proved him correct. For this, the comet was named after Encke. It was only the second comet known to be periodic (hence the “2P”), the first being Halley’s.
The orbit is quite stable, and with a period of 3.3 years apparitions repeat on a 10-year cycle. This year the comet is well seen from the Northern Hemisphere prior to perihelion, which is in late December. The comet tracks through Andromeda during October and early November, then accelerates southwards through Cygnus and begins December in Ophiuchus.
The comet will be observable naked eye in the Southern Hemisphere until mid-January, when it will be it’s brightest. After that it will get farther away but higher in the sky which will make for some good photo opportunities. Below is the view from Sydney, Australia showing Enke’s projected path and apparent magnitude.