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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.

Comet Encke (2P/Encke) as imaged by the Spacewatch Telescope on Kitt Peak in 1994 (JPL/Jim Scotti)

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

Comet Encke Finder Chart from October 1 to October 13, 2013 - pdf format

Comet Encke Finder Chart from October 12 to October 23, 2013

Comet Encke Finder Chart from October 12 to October 23, 2013 - pdf format

Comet Encke Finder Chart from October 21 to October 31, 2013

Comet Encke Finder Chart from October 21 to October 31, 2013 - pdf format

Comet 2P/Encke Data Table (at epoch August 21, 2012)

Name2P/Encke
TypeComet
ClassificationEncke-type comet (NEO)
DiscovererPierre Méchain, Johann Franz Encke first recognised the periodicity
Discovery date1786 (orbit computed by Encke in 1819)
Aphelion (AU)4.09236
Perihelion (AU)0.33625
Semi-major axis (AU) 2.21430
Eccentricity0.84815
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
NotesComet Encke has the shortest orbital period of any known comet

Comet Encke (2P/Encke) Data Table

DateRight AscensionDeclinationEstimated MagnitudeDistance from Earth (AU)Constellation
01 Oct 201306h 51m 09s43d 25m 38s10.20.604Auriga
02 Oct 201307h 01m 43s43d 31m 57s10.00.590Auriga
03 Oct 201307h 12m 43s43d 34m 46s9.80.577Auriga
04 Oct 201307h 24m 11s43d 33m 33s9.60.565Auriga
05 Oct 201307h 36m 05s43d 27m 50s9.40.553Lynx
06 Oct 201307h 48m 23s43d 17m 05s9.20.542Lynx
07 Oct 201308h 01m 03s43d 00m 47s9.00.532Lynx
08 Oct 201308h 14m 02s42d 38m 29s9.00.522Lynx
09 Oct 201308h 27m 17s42d 09m 44s8.90.513Lynx
10 Oct 201308h 40m 44s41d 34m 12s8.80.505Lynx
11 Oct 201308h 54m 18s40d 51m 36s8.80.499Lynx
12 Oct 201309h 07m 54s40d 01m 49s8.70.492Lynx
13 Oct 201309h 21m 28s39d 04m 47s8.60.487Lynx
14 Oct 201309h 34m 55s38d 00m 40s8.50.483Leo Minor
15 Oct 201309h 48m 11s36d 49m 43s8.50.480Leo Minor
16 Oct 201310h 01m 11s35d 32m 20s8.40.479Leo Minor
17 Oct 201310h 13m 53s34d 09m 03s8.30.478Leo Minor
18 Oct 201310h 26m 13s32d 40m 28s8.30.478Leo Minor
19 Oct 201310h 38m 09s31d 07m 20s8.20.480Leo Minor
20 Oct 201310h 49m 39s29d 30m 24s8.20.482Leo Minor
21 Oct 201311h 00m 43s27d 50m 27s8.10.486Leo Minor
22 Oct 201311h 11m 20s26d 08m 18s8.10.491Leo
23 Oct 201311h 21m 30s24d 24m 40s8.00.497Leo
24 Oct 201311h 31m 13s22d 40m 18s8.00.504Leo
25 Oct 201311h 40m 31s20d 55m 50s8.00.513Leo
26 Oct 201311h 49m 23s19d 11m 52s7.90.522Leo
27 Oct 201311h 57m 51s17d 28m 52s7.90.533Leo
28 Oct 201312h 05m 57s15d 47m 16s7.90.544Coma Berenices
29 Oct 201312h 13m 42s14d 07m 23s7.80.557Coma Berenices
30 Oct 201312h 21m 07s12d 29m 29s7.80.570Virgo
31 Oct 201312h 28m 14s10d 53m 45s7.80.585Virgo
01 Nov 201312h 35m 04s09d 20m 19s7.70.600Virgo
02 Nov 201312h 41m 39s07d 49m 14s7.70.617Virgo
03 Nov 201312h 48m 00s06d 20m 31s7.70.634Virgo
04 Nov 201312h 54m 10s04d 54m 09s7.60.652Virgo
05 Nov 201313h 00m 08s03d 30m 05s7.60.671Virgo
06 Nov 201313h 05m 58s02d 08m 13s7.60.692Virgo
07 Nov 201313h 11m 40s00d 48m 28s7.50.712Virgo
08 Nov 201313h 17m 16s-00d 29m 19s7.50.734Virgo
09 Nov 201313h 22m 48s-01d 45m 14s7.40.757Virgo
10 Nov 201313h 28m 17s-02d 59m 25s7.40.781Virgo
11 Nov 201313h 33m 45s-04d 12m 02s7.30.805Virgo
12 Nov 201313h 39m 14s-05d 23m 11s7.30.830Virgo
13 Nov 201313h 44m 44s-06d 32m 59s7.20.856Virgo
14 Nov 201313h 50m 19s-07d 41m 34s7.20.883Virgo
15 Nov 201313h 55m 59s-08d 48m 59s7.20.911Virgo
16 Nov 201314h 01m 46s-09d 55m 18s7.10.939Virgo
17 Nov 201314h 07m 42s-11d 00m 30s7.10.968Virgo
18 Nov 201314h 13m 47s-12d 04m 33s7.10.997Virgo
19 Nov 201314h 20m 02s-13d 07m 23s7.11.026Virgo
20 Nov 201314h 26m 29s-14d 08m 51s7.11.056Libra
21 Nov 201314h 33m 06s-15d 08m 47s7.21.085Libra
22 Nov 201314h 39m 53s-16d 06m 58s7.21.114Libra
23 Nov 201314h 46m 50s-17d 03m 12s7.31.143Libra
24 Nov 201314h 53m 54s-17d 57m 15s7.41.172Libra
25 Nov 201315h 01m 05s-18d 48m 57s7.51.199Libra
26 Nov 201315h 08m 20s-19d 38m 08s7.61.226Libra
27 Nov 201315h 15m 37s-20d 24m 41s7.71.253Libra
28 Nov 201315h 22m 56s-21d 08m 34s7.91.278Libra
29 Nov 201315h 30m 14s-21d 49m 44s8.01.303Libra
30 Nov 201315h 37m 31s-22d 28m 13s8.21.327Libra
01 Dec 201315h 44m 44s-23d 04m 04s8.31.351Libra
02 Dec 201315h 51m 53s-23d 37m 22s8.51.374Scorpius
03 Dec 201315h 58m 58s-24d 08m 11s8.61.396Scorpius
04 Dec 201316h 05m 57s-24d 36m 37s8.71.418Scorpius
05 Dec 201316h 12m 50s-25d 02m 48s8.91.440Scorpius
06 Dec 201316h 19m 37s-25d 26m 50s9.01.461Scorpius
07 Dec 201316h 26m 17s-25d 48m 49s9.21.482Scorpius
08 Dec 201316h 32m 51s-26d 08m 53s9.31.502Scorpius
09 Dec 201316h 39m 18s-26d 27m 07s9.41.523Scorpius
10 Dec 201316h 45m 38s-26d 43m 37s9.61.543Scorpius
11 Dec 201316h 51m 51s-26d 58m 31s9.71.562Scorpius
12 Dec 201316h 57m 58s-27d 11m 53s9.91.582Ophiuchus
13 Dec 201317h 03m 57s-27d 23m 49s10.21.601Ophiuchus
14 Dec 201317h 09m 50s-27d 34m 24s10.41.620Ophiuchus
15 Dec 201317h 15m 36s-27d 43m 43s10.61.639Ophiuchus
16 Dec 201317h 21m 15s-27d 51m 51s10.81.658Ophiuchus
17 Dec 201317h 26m 48s-27d 58m 51s11.01.677Ophiuchus
18 Dec 201317h 32m 14s-28d 04m 49s11.21.695Ophiuchus
19 Dec 201317h 37m 34s-28d 09m 47s11.41.714Ophiuchus
20 Dec 201317h 42m 48s-28d 13m 50s11.61.732Ophiuchus
21 Dec 201317h 47m 56s-28d 17m 00s11.81.750Sagittarius
22 Dec 201317h 52m 58s-28d 19m 22s12.01.768Sagittarius
23 Dec 201317h 57m 54s-28d 20m 58s12.11.786Sagittarius
24 Dec 201318h 02m 44s-28d 21m 51s12.31.804Sagittarius
25 Dec 201318h 07m 29s-28d 22m 03s12.51.822Sagittarius
26 Dec 201318h 12m 08s-28d 21m 38s12.61.839Sagittarius
27 Dec 201318h 16m 43s-28d 20m 37s12.81.857Sagittarius
28 Dec 201318h 21m 11s-28d 19m 02s12.91.874Sagittarius
29 Dec 201318h 25m 35s-28d 16m 57s13.11.891Sagittarius
30 Dec 201318h 29m 54s-28d 14m 22s13.21.908Sagittarius
31 Dec 201318h 34m 09s-28d 11m 20s13.41.925Sagittarius