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)
| Date | Right Ascension | Declination | Estimated Magnitude | Distance from Earth (AU) | Constellation |
|---|---|---|---|---|---|
| 01 Feb 2017 | 23h 37m 01s | +06d 23m 53s | +10.5 | 1.266 | Pisces |
| 02 Feb 2017 | 23h 38m 29s | +06d 29m 53s | +10.5 | 1.256 | Pisces |
| 03 Feb 2017 | 23h 39m 57s | +06d 35m 53s | +10.4 | 1.245 | Pisces |
| 04 Feb 2017 | 23h 41m 27s | +06d 41m 50s | +10.3 | 1.234 | Pisces |
| 05 Feb 2017 | 23h 42m 56s | +06d 47m 43s | +10.2 | 1.223 | Pisces |
| 06 Feb 2017 | 23h 44m 27s | +06d 53m 31s | +10.1 | 1.211 | Pisces |
| 07 Feb 2017 | 23h 45m 57s | +06d 59m 11s | +10.1 | 1.199 | Pisces |
| 08 Feb 2017 | 23h 47m 28s | +07d 04m 41s | +10.0 | 1.186 | Pisces |
| 09 Feb 2017 | 23h 48m 59s | +07d 09m 59s | +9.9 | 1.173 | Pisces |
| 10 Feb 2017 | 23h 50m 30s | +07d 15m 03s | +9.8 | 1.160 | Pisces |
| 11 Feb 2017 | 23h 52m 01s | +07d 19m 49s | +9.7 | 1.146 | Pisces |
| 12 Feb 2017 | 23h 53m 31s | +07d 24m 14s | +9.6 | 1.131 | Pisces |
| 13 Feb 2017 | 23h 55m 01s | +07d 28m 14s | +9.5 | 1.116 | Pisces |
| 14 Feb 2017 | 23h 56m 29s | +07d 31m 45s | +9.3 | 1.101 | Pisces |
| 15 Feb 2017 | 23h 57m 56s | +07d 34m 41s | +9.2 | 1.085 | Pisces |
| 16 Feb 2017 | 23h 59m 21s | +07d 36m 56s | +9.1 | 1.069 | Pisces |
| 17 Feb 2017 | 00h 00m 43s | +07d 38m 25s | +9.0 | 1.052 | Pisces |
| 18 Feb 2017 | 00h 02m 03s | +07d 38m 58s | +8.9 | 1.034 | Pisces |
| 19 Feb 2017 | 00h 03m 18s | +07d 38m 27s | +8.7 | 1.016 | Pisces |
| 20 Feb 2017 | 00h 04m 30s | +07d 36m 42s | +8.6 | 0.998 | Pisces |
| 21 Feb 2017 | 00h 05m 35s | +07d 33m 30s | +8.5 | 0.979 | Pisces |
| 22 Feb 2017 | 00h 06m 34s | +07d 28m 38s | +8.3 | 0.960 | Pisces |
| 23 Feb 2017 | 00h 07m 24s | +07d 21m 49s | +8.2 | 0.940 | Pisces |
| 24 Feb 2017 | 00h 08m 06s | +07d 12m 44s | +8.0 | 0.919 | Pisces |
| 25 Feb 2017 | 00h 08m 35s | +07d 01m 02s | +7.8 | 0.899 | Pisces |
| 26 Feb 2017 | 00h 08m 51s | +06d 46m 19s | +7.7 | 0.878 | Pisces |
| 27 Feb 2017 | 00h 08m 52s | +06d 28m 06s | +7.5 | 0.856 | Pisces |
| 28 Feb 2017 | 00h 08m 33s | +06d 05m 52s | +7.3 | 0.835 | Pisces |
| 01 Mar 2017 | 00h 07m 53s | +05d 39m 04s | +7.2 | 0.813 | Pisces |
| 02 Mar 2017 | 00h 06m 49s | +05d 07m 05s | +7.0 | 0.792 | Pisces |
| 03 Mar 2017 | 00h 05m 16s | +04d 29m 21s | +6.9 | 0.771 | Pisces |
| 04 Mar 2017 | 00h 03m 12s | +03d 45m 16s | +6.7 | 0.751 | Pisces |
| 05 Mar 2017 | 00h 00m 34s | +02d 54m 25s | +6.5 | 0.732 | Pisces |
| 06 Mar 2017 | 23h 57m 21s | +01d 56m 31s | +6.4 | 0.714 | Pisces |
| 07 Mar 2017 | 23h 53m 30s | +00d 51m 38s | +6.1 | 0.698 | Pisces |
| 08 Mar 2017 | 23h 49m 04s | -00d 19m 49s | +6.0 | 0.684 | Pisces |
| 09 Mar 2017 | 23h 44m 06s | -01d 36m 54s | +5.8 | 0.672 | Pisces |
| 10 Mar 2017 | 23h 38m 40s | -02d 58m 17s | +5.7 | 0.664 | Pisces |
| 11 Mar 2017 | 23h 32m 54s | -04d 22m 09s | +5.7 | 0.658 | Aquarius |
| 12 Mar 2017 | 23h 26m 57s | -05d 46m 33s | +5.8 | 0.655 | Aquarius |
| 13 Mar 2017 | 23h 20m 58s | -07d 09m 25s | +6.0 | 0.656 | Aquarius |
| 14 Mar 2017 | 23h 15m 06s | -08d 28m 56s | +6.1 | 0.659 | Aquarius |
| 15 Mar 2017 | 23h 09m 29s | -09d 43m 40s | +6.3 | 0.665 | Aquarius |
| 16 Mar 2017 | 23h 04m 12s | -10d 52m 34s | +6.4 | 0.674 | Aquarius |
| 17 Mar 2017 | 22h 59m 21s | -11d 55m 04s | +6.6 | 0.684 | Aquarius |
| 18 Mar 2017 | 22h 54m 57s | -12d 50m 60s | +6.8 | 0.696 | Aquarius |
| 19 Mar 2017 | 22h 51m 02s | -13d 40m 29s | +6.9 | 0.709 | Aquarius |
| 20 Mar 2017 | 22h 47m 35s | -14d 23m 51s | +7.0 | 0.724 | Aquarius |
| 21 Mar 2017 | 22h 44m 35s | -15d 01m 34s | +7.2 | 0.739 | Aquarius |
| 22 Mar 2017 | 22h 42m 01s | -15d 34m 09s | +7.3 | 0.754 | Aquarius |
| 23 Mar 2017 | 22h 39m 50s | -16d 02m 08s | +7.5 | 0.770 | Aquarius |
| 24 Mar 2017 | 22h 38m 01s | -16d 26m 03s | +7.6 | 0.786 | Aquarius |
| 25 Mar 2017 | 22h 36m 31s | -16d 46m 23s | +7.8 | 0.802 | Aquarius |
| 26 Mar 2017 | 22h 35m 18s | -17d 03m 33s | +7.9 | 0.817 | Aquarius |
| 27 Mar 2017 | 22h 34m 21s | -17d 17m 59s | +8.1 | 0.833 | Aquarius |
| 28 Mar 2017 | 22h 33m 37s | -17d 30m 02s | +8.2 | 0.849 | Aquarius |
| 29 Mar 2017 | 22h 33m 06s | -17d 39m 59s | +8.4 | 0.864 | Aquarius |
| 30 Mar 2017 | 22h 32m 44s | -17d 48m 07s | +8.5 | 0.879 | Aquarius |
| 31 Mar 2017 | 22h 32m 32s | -17d 54m 41s | +8.8 | 0.893 | Aquarius |
| 01 Apr 2017 | 22h 32m 28s | -17d 59m 52s | +9.1 | 0.907 | Aquarius |
| 02 Apr 2017 | 22h 32m 31s | -18d 03m 53s | +9.3 | 0.921 | Aquarius |
| 03 Apr 2017 | 22h 32m 40s | -18d 06m 51s | +9.5 | 0.934 | Aquarius |
| 04 Apr 2017 | 22h 32m 55s | -18d 08m 55s | +9.7 | 0.947 | Aquarius |
| 05 Apr 2017 | 22h 33m 14s | -18d 10m 12s | +9.9 | 0.960 | Aquarius |
| 06 Apr 2017 | 22h 33m 36s | -18d 10m 48s | +10.1 | 0.972 | Aquarius |
| 07 Apr 2017 | 22h 34m 03s | -18d 10m 50s | +10.3 | 0.984 | Aquarius |
| 08 Apr 2017 | 22h 34m 32s | -18d 10m 21s | +10.5 | 0.995 | Aquarius |
| 09 Apr 2017 | 22h 35m 04s | -18d 09m 26s | +10.7 | 1.006 | Aquarius |
| 10 Apr 2017 | 22h 35m 38s | -18d 08m 08s | +10.9 | 1.017 | Aquarius |
| 11 Apr 2017 | 22h 36m 13s | -18d 06m 31s | +11.0 | 1.027 | Aquarius |
| 12 Apr 2017 | 22h 36m 50s | -18d 04m 38s | +11.2 | 1.037 | Aquarius |
| 13 Apr 2017 | 22h 37m 29s | -18d 02m 32s | +11.4 | 1.047 | Aquarius |
| 14 Apr 2017 | 22h 38m 08s | -18d 00m 14s | +11.5 | 1.056 | Aquarius |
| 15 Apr 2017 | 22h 38m 48s | -17d 57m 47s | +11.7 | 1.065 | Aquarius |
| 16 Apr 2017 | 22h 39m 28s | -17d 55m 13s | +11.8 | 1.073 | Aquarius |
| 17 Apr 2017 | 22h 40m 09s | -17d 52m 33s | +12.0 | 1.081 | Aquarius |
| 18 Apr 2017 | 22h 40m 49s | -17d 49m 49s | +12.1 | 1.089 | Aquarius |
| 19 Apr 2017 | 22h 41m 30s | -17d 47m 02s | +12.2 | 1.096 | Aquarius |
| 20 Apr 2017 | 22h 42m 11s | -17d 44m 14s | +12.4 | 1.103 | Aquarius |
| 21 Apr 2017 | 22h 42m 51s | -17d 41m 26s | +12.5 | 1.110 | Aquarius |
| 22 Apr 2017 | 22h 43m 31s | -17d 38m 38s | +12.6 | 1.116 | Aquarius |
| 23 Apr 2017 | 22h 44m 11s | -17d 35m 52s | +12.7 | 1.122 | Aquarius |
| 24 Apr 2017 | 22h 44m 50s | -17d 33m 09s | +12.9 | 1.128 | Aquarius |
| 25 Apr 2017 | 22h 45m 28s | -17d 30m 29s | +13.0 | 1.134 | Aquarius |
| 26 Apr 2017 | 22h 46m 05s | -17d 27m 54s | +13.1 | 1.139 | Aquarius |
| 27 Apr 2017 | 22h 46m 42s | -17d 25m 23s | +13.2 | 1.144 | Aquarius |
| 28 Apr 2017 | 22h 47m 17s | -17d 22m 58s | +13.3 | 1.148 | Aquarius |
| 29 Apr 2017 | 22h 47m 52s | -17d 20m 39s | +13.4 | 1.153 | Aquarius |
| 30 Apr 2017 | 22h 48m 25s | -17d 18m 26s | +13.5 | 1.157 | Aquarius |