Comet Encke is a periodic comet with an orbital period of 3.3 years - the shortest period of any known comet. Its official designation is 2P/Encke and as the name suggests this was the second period comet to be discovered; the first was the most famous comet of all, Halley (1P/Halley). It's currently brightening in the morning skies as it heads towards perihelion and should by the end of October be visible with binoculars.
Discovery
Like Halley's Comet, Encke is unusual in that it was named after the person who first calculated its orbit rather than its discoverer. It's rare for this to happen but there are a few cases, especially centuries ago.
Comet 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 realized 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, Comet Encke has been observed at every perihelion except for one in 1944, during World War II.
This year on November 21st, it will be the 62nd recorded return to perihelion for Comet Encke. The comet will approach to within 0.33625 AU (approx. 50.30 million kilometres or 31.26 million miles) of the Sun and for a number of days either side of this, should be bright enough to be visible with binoculars.
Location, magnitude and star chart
During October, Encke is well placed in the morning sky for observers based at Northern temperate latitudes and reasonable well placed from the tropics. In the Southern Hemisphere, it's observable only for the first half of the month.
Encke moves in a south-eastward direction against the "fixed" stars during October. It starts the month in Auriga, moves into Lynx on October 4th and then into Leo Minor on October 13th. The comet remains here until October 21st when it crosses into Leo, staying there for about a week before briefly passing through Coma Berenices from October 27th to 29th. It then moves into Virgo, where it remains for the rest of the month. It's estimated that Encke will brighten from magnitude +10.2 to +7.8 during October.
For the early part of the month, a medium 150mm (6-inch) or 200mm (8-inch) telescope is recommended to find Encke; however it might also be spotted with a smaller instrument. Encke makes it closest approach to Earth on October 17, shining at mag +8.3 in Leo Minor. Once it reaches (hopefully!) magnitude +8.0 (est. October 23rd) then Encke should be a much easier small telescope target (e.g. 80mm refractor) and even within the range of binoculars. At the end of October the comet passes through the galaxy rich field of northern Virgo.
The finder charts below show the positions of comet Encke from October 1 to October 31, 2013.
Comet Encke Finder Chart from October 1 to October 13, 2013 - pdf format
Comet Encke Finder Chart from October 12 to October 23, 2013 - pdf format
Comet Encke Finder Chart from October 21 to October 31, 2013 - pdf format
Comet 2P/Encke Data Table (at epoch August 21, 2012)
| 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 (AU) | 4.09236 |
| Perihelion (AU) | 0.33625 |
| Semi-major axis (AU) | 2.21430 |
| Eccentricity | 0.84815 |
| Orbital period (years) | 3.29513 |
| Inclination (degrees) | 11.7773 |
| Longitude of ascending node (degrees) | 334.572 |
| Last perihelion | August 6th, 2010 |
| Next perihelion | November 21st, 2013 |
| Notes | Comet Encke has the shortest orbital period of any known comet |
Comet Encke (2P/Encke) Data Table
| Date | Right Ascension | Declination | Estimated Magnitude | Distance from Earth (AU) | Constellation |
|---|---|---|---|---|---|
| 01 Oct 2013 | 06h 51m 09s | 43d 25m 38s | 10.2 | 0.604 | Auriga |
| 02 Oct 2013 | 07h 01m 43s | 43d 31m 57s | 10.0 | 0.590 | Auriga |
| 03 Oct 2013 | 07h 12m 43s | 43d 34m 46s | 9.8 | 0.577 | Auriga |
| 04 Oct 2013 | 07h 24m 11s | 43d 33m 33s | 9.6 | 0.565 | Auriga |
| 05 Oct 2013 | 07h 36m 05s | 43d 27m 50s | 9.4 | 0.553 | Lynx |
| 06 Oct 2013 | 07h 48m 23s | 43d 17m 05s | 9.2 | 0.542 | Lynx |
| 07 Oct 2013 | 08h 01m 03s | 43d 00m 47s | 9.0 | 0.532 | Lynx |
| 08 Oct 2013 | 08h 14m 02s | 42d 38m 29s | 9.0 | 0.522 | Lynx |
| 09 Oct 2013 | 08h 27m 17s | 42d 09m 44s | 8.9 | 0.513 | Lynx |
| 10 Oct 2013 | 08h 40m 44s | 41d 34m 12s | 8.8 | 0.505 | Lynx |
| 11 Oct 2013 | 08h 54m 18s | 40d 51m 36s | 8.8 | 0.499 | Lynx |
| 12 Oct 2013 | 09h 07m 54s | 40d 01m 49s | 8.7 | 0.492 | Lynx |
| 13 Oct 2013 | 09h 21m 28s | 39d 04m 47s | 8.6 | 0.487 | Lynx |
| 14 Oct 2013 | 09h 34m 55s | 38d 00m 40s | 8.5 | 0.483 | Leo Minor |
| 15 Oct 2013 | 09h 48m 11s | 36d 49m 43s | 8.5 | 0.480 | Leo Minor |
| 16 Oct 2013 | 10h 01m 11s | 35d 32m 20s | 8.4 | 0.479 | Leo Minor |
| 17 Oct 2013 | 10h 13m 53s | 34d 09m 03s | 8.3 | 0.478 | Leo Minor |
| 18 Oct 2013 | 10h 26m 13s | 32d 40m 28s | 8.3 | 0.478 | Leo Minor |
| 19 Oct 2013 | 10h 38m 09s | 31d 07m 20s | 8.2 | 0.480 | Leo Minor |
| 20 Oct 2013 | 10h 49m 39s | 29d 30m 24s | 8.2 | 0.482 | Leo Minor |
| 21 Oct 2013 | 11h 00m 43s | 27d 50m 27s | 8.1 | 0.486 | Leo Minor |
| 22 Oct 2013 | 11h 11m 20s | 26d 08m 18s | 8.1 | 0.491 | Leo |
| 23 Oct 2013 | 11h 21m 30s | 24d 24m 40s | 8.0 | 0.497 | Leo |
| 24 Oct 2013 | 11h 31m 13s | 22d 40m 18s | 8.0 | 0.504 | Leo |
| 25 Oct 2013 | 11h 40m 31s | 20d 55m 50s | 8.0 | 0.513 | Leo |
| 26 Oct 2013 | 11h 49m 23s | 19d 11m 52s | 7.9 | 0.522 | Leo |
| 27 Oct 2013 | 11h 57m 51s | 17d 28m 52s | 7.9 | 0.533 | Leo |
| 28 Oct 2013 | 12h 05m 57s | 15d 47m 16s | 7.9 | 0.544 | Coma Berenices |
| 29 Oct 2013 | 12h 13m 42s | 14d 07m 23s | 7.8 | 0.557 | Coma Berenices |
| 30 Oct 2013 | 12h 21m 07s | 12d 29m 29s | 7.8 | 0.570 | Virgo |
| 31 Oct 2013 | 12h 28m 14s | 10d 53m 45s | 7.8 | 0.585 | Virgo |
| 01 Nov 2013 | 12h 35m 04s | 09d 20m 19s | 7.7 | 0.600 | Virgo |
| 02 Nov 2013 | 12h 41m 39s | 07d 49m 14s | 7.7 | 0.617 | Virgo |
| 03 Nov 2013 | 12h 48m 00s | 06d 20m 31s | 7.7 | 0.634 | Virgo |
| 04 Nov 2013 | 12h 54m 10s | 04d 54m 09s | 7.6 | 0.652 | Virgo |
| 05 Nov 2013 | 13h 00m 08s | 03d 30m 05s | 7.6 | 0.671 | Virgo |
| 06 Nov 2013 | 13h 05m 58s | 02d 08m 13s | 7.6 | 0.692 | Virgo |
| 07 Nov 2013 | 13h 11m 40s | 00d 48m 28s | 7.5 | 0.712 | Virgo |
| 08 Nov 2013 | 13h 17m 16s | -00d 29m 19s | 7.5 | 0.734 | Virgo |
| 09 Nov 2013 | 13h 22m 48s | -01d 45m 14s | 7.4 | 0.757 | Virgo |
| 10 Nov 2013 | 13h 28m 17s | -02d 59m 25s | 7.4 | 0.781 | Virgo |
| 11 Nov 2013 | 13h 33m 45s | -04d 12m 02s | 7.3 | 0.805 | Virgo |
| 12 Nov 2013 | 13h 39m 14s | -05d 23m 11s | 7.3 | 0.830 | Virgo |
| 13 Nov 2013 | 13h 44m 44s | -06d 32m 59s | 7.2 | 0.856 | Virgo |
| 14 Nov 2013 | 13h 50m 19s | -07d 41m 34s | 7.2 | 0.883 | Virgo |
| 15 Nov 2013 | 13h 55m 59s | -08d 48m 59s | 7.2 | 0.911 | Virgo |
| 16 Nov 2013 | 14h 01m 46s | -09d 55m 18s | 7.1 | 0.939 | Virgo |
| 17 Nov 2013 | 14h 07m 42s | -11d 00m 30s | 7.1 | 0.968 | Virgo |
| 18 Nov 2013 | 14h 13m 47s | -12d 04m 33s | 7.1 | 0.997 | Virgo |
| 19 Nov 2013 | 14h 20m 02s | -13d 07m 23s | 7.1 | 1.026 | Virgo |
| 20 Nov 2013 | 14h 26m 29s | -14d 08m 51s | 7.1 | 1.056 | Libra |
| 21 Nov 2013 | 14h 33m 06s | -15d 08m 47s | 7.2 | 1.085 | Libra |
| 22 Nov 2013 | 14h 39m 53s | -16d 06m 58s | 7.2 | 1.114 | Libra |
| 23 Nov 2013 | 14h 46m 50s | -17d 03m 12s | 7.3 | 1.143 | Libra |
| 24 Nov 2013 | 14h 53m 54s | -17d 57m 15s | 7.4 | 1.172 | Libra |
| 25 Nov 2013 | 15h 01m 05s | -18d 48m 57s | 7.5 | 1.199 | Libra |
| 26 Nov 2013 | 15h 08m 20s | -19d 38m 08s | 7.6 | 1.226 | Libra |
| 27 Nov 2013 | 15h 15m 37s | -20d 24m 41s | 7.7 | 1.253 | Libra |
| 28 Nov 2013 | 15h 22m 56s | -21d 08m 34s | 7.9 | 1.278 | Libra |
| 29 Nov 2013 | 15h 30m 14s | -21d 49m 44s | 8.0 | 1.303 | Libra |
| 30 Nov 2013 | 15h 37m 31s | -22d 28m 13s | 8.2 | 1.327 | Libra |
| 01 Dec 2013 | 15h 44m 44s | -23d 04m 04s | 8.3 | 1.351 | Libra |
| 02 Dec 2013 | 15h 51m 53s | -23d 37m 22s | 8.5 | 1.374 | Scorpius |
| 03 Dec 2013 | 15h 58m 58s | -24d 08m 11s | 8.6 | 1.396 | Scorpius |
| 04 Dec 2013 | 16h 05m 57s | -24d 36m 37s | 8.7 | 1.418 | Scorpius |
| 05 Dec 2013 | 16h 12m 50s | -25d 02m 48s | 8.9 | 1.440 | Scorpius |
| 06 Dec 2013 | 16h 19m 37s | -25d 26m 50s | 9.0 | 1.461 | Scorpius |
| 07 Dec 2013 | 16h 26m 17s | -25d 48m 49s | 9.2 | 1.482 | Scorpius |
| 08 Dec 2013 | 16h 32m 51s | -26d 08m 53s | 9.3 | 1.502 | Scorpius |
| 09 Dec 2013 | 16h 39m 18s | -26d 27m 07s | 9.4 | 1.523 | Scorpius |
| 10 Dec 2013 | 16h 45m 38s | -26d 43m 37s | 9.6 | 1.543 | Scorpius |
| 11 Dec 2013 | 16h 51m 51s | -26d 58m 31s | 9.7 | 1.562 | Scorpius |
| 12 Dec 2013 | 16h 57m 58s | -27d 11m 53s | 9.9 | 1.582 | Ophiuchus |
| 13 Dec 2013 | 17h 03m 57s | -27d 23m 49s | 10.2 | 1.601 | Ophiuchus |
| 14 Dec 2013 | 17h 09m 50s | -27d 34m 24s | 10.4 | 1.620 | Ophiuchus |
| 15 Dec 2013 | 17h 15m 36s | -27d 43m 43s | 10.6 | 1.639 | Ophiuchus |
| 16 Dec 2013 | 17h 21m 15s | -27d 51m 51s | 10.8 | 1.658 | Ophiuchus |
| 17 Dec 2013 | 17h 26m 48s | -27d 58m 51s | 11.0 | 1.677 | Ophiuchus |
| 18 Dec 2013 | 17h 32m 14s | -28d 04m 49s | 11.2 | 1.695 | Ophiuchus |
| 19 Dec 2013 | 17h 37m 34s | -28d 09m 47s | 11.4 | 1.714 | Ophiuchus |
| 20 Dec 2013 | 17h 42m 48s | -28d 13m 50s | 11.6 | 1.732 | Ophiuchus |
| 21 Dec 2013 | 17h 47m 56s | -28d 17m 00s | 11.8 | 1.750 | Sagittarius |
| 22 Dec 2013 | 17h 52m 58s | -28d 19m 22s | 12.0 | 1.768 | Sagittarius |
| 23 Dec 2013 | 17h 57m 54s | -28d 20m 58s | 12.1 | 1.786 | Sagittarius |
| 24 Dec 2013 | 18h 02m 44s | -28d 21m 51s | 12.3 | 1.804 | Sagittarius |
| 25 Dec 2013 | 18h 07m 29s | -28d 22m 03s | 12.5 | 1.822 | Sagittarius |
| 26 Dec 2013 | 18h 12m 08s | -28d 21m 38s | 12.6 | 1.839 | Sagittarius |
| 27 Dec 2013 | 18h 16m 43s | -28d 20m 37s | 12.8 | 1.857 | Sagittarius |
| 28 Dec 2013 | 18h 21m 11s | -28d 19m 02s | 12.9 | 1.874 | Sagittarius |
| 29 Dec 2013 | 18h 25m 35s | -28d 16m 57s | 13.1 | 1.891 | Sagittarius |
| 30 Dec 2013 | 18h 29m 54s | -28d 14m 22s | 13.2 | 1.908 | Sagittarius |
| 31 Dec 2013 | 18h 34m 09s | -28d 11m 20s | 13.4 | 1.925 | Sagittarius |