Discovery, Orbit and Size
Despite the name, comet 38P/Stephan-Oterma was discovered by Jerome Coggia at the Marseilles
Observatory in January 1867, but the name was awarded to E J M Stephan, the Observatory Director as he first calculated the position with accuracy. This comet has an orbital period of 38 years defined as a Halley-type comet hence why it was last observed in 1980/1. The size of the comet’s nucleus is currently unknown.
Perihelion on 38P occurs on 26 August, 2018 by which time it should become sufficiently bright enough for backyard telescopes. On the night of 08/09 November, Comet 38p will lie very close to deep sky object NGC 2392 (The Eskimo Nebula) separated by just 8 arcmins, a good photographic opportunity. The comet will remain well placed in the evening skies for the remainder of the year and on in to 2019 when it becomes almost circumpolar in the constellation of Lynx.
According to NASA’s JPL orbit program, the point at which the Earth is closest to the comet is not actually until January 2019 as the Earth ‘catches up’ with the comet during it’s orbit around the Sun. How bright the icy rock will be will depend on how it reacts to its perihelion passage.