Comet Encke (2P/Encke) now visible in the western sky during evening twilight

During the second half of February, comet Encke will be visible with small telescopes in evening sky above the western horizon just after sunset. This periodic comet, officially designated as 2P/Encke, is now rapidly brightening and will continue to do so until it reaches perihelion on March 10th. On February 17th, it shone at mag. +9.0 and therefore bright enough to be seen with small/medium size scopes. By the end of month, it's expected to have improved to mag. +7.3 and within binocular range. However, it will be a challenging binocular object - not because of its magnitude - but due to its low altitude at dusk.

Today, it's common practice to name comets after the individual or individuals who discovered them. In recent years, large teams of astronomers have discovered many comets and in such cases they are often named after the collaboration or the instrument used. However, in the past the same rule didn't always apply. For example, the first three periodic comets, Halley's, Encke's and Biela's, were all named after the astronomers who calculated their orbits rather than their original discoverers.

Encke was discovered by Pierre Méchain in 1786, but not recognized as a periodic comet until 1819, when German astronomer Johann Franz Encke first computed its orbit. He realised that the comet seen by Jean-Louis Pons in 1818, was the same comet as that seen by Pons in 1805, Caroline Herschel in 1795 and Méchain in 1786. Encke then correctly predicted its next return in 1822. Since 1818, Encke has been observed at every perihelion, except in 1944 during World War II.

Encke remains low down during the latter part of February and early March, before it disappears behind the Sun for a short time. It then re-emerges in the Southern Hemisphere morning sky during late March, staying observable while fading. From northern locations, the next couple of weeks offers the best chance to spot the comet, before it passes behind the Sun.

The illustrations below show the view, one hour after sunset, during February and early March from mid-latitude northern locations such as London, New York City and Paris. From southern and tropical locations, Encke is also visible but appears even lower down during this time.

Comet 2P/Encke (at epoch February 16, 2017)

Name 2P/Encke Type Comet Classification Encke-type comet (NEO) Discoverer Pierre Méchain, Johann Franz Encke first recognised the periodicity Discovery date 1786 (orbit computed by Encke in 1819) Aphelion distance (AU) 4.09352 Perihelion distance (AU) 0.33589 Semi-major axis (AU) 2.21471 Eccentricity 0.84833 Orbital period (years) 3.29604 Inclination (degrees) 11.7782 Longitude of ascending node (degrees) 334.560 Last perihelion November 21, 2013 Next perihelion March 10, 2017 Notes Comet Encke has the shortest orbital period of any known comet

Comet Encke (2P/Encke)