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.

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

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.

Position of Encke, one hour after sunset, on February 21, 2017 from mid-latitude northern locations (credit:- stellarium/freestarcharts)

Position of Encke, one hour after sunset, on February 25, 2017 from mid-latitude northern locations (credit:- stellarium/freestarcharts)

Position of Encke, one hour after sunset, on March 1, 2017 from mid-latitude northern locations (credit:- stellarium/freestarcharts)

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

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 distance (AU)4.09352
Perihelion distance (AU)0.33589
Semi-major axis (AU) 2.21471
Eccentricity0.84833
Orbital period (years)3.29604
Inclination (degrees) 11.7782
Longitude of ascending node (degrees)334.560
Last perihelionNovember 21, 2013
Next perihelionMarch 10, 2017
NotesComet Encke has the shortest orbital period of any known comet

Comet Encke (2P/Encke)

DateRight AscensionDeclinationEstimated MagnitudeDistance from Earth (AU)Constellation
01 Feb 201723h 37m 01s+06d 23m 53s+10.51.266Pisces
02 Feb 201723h 38m 29s+06d 29m 53s+10.51.256Pisces
03 Feb 201723h 39m 57s+06d 35m 53s+10.41.245Pisces
04 Feb 201723h 41m 27s+06d 41m 50s+10.31.234Pisces
05 Feb 201723h 42m 56s+06d 47m 43s+10.21.223Pisces
06 Feb 201723h 44m 27s+06d 53m 31s+10.11.211Pisces
07 Feb 201723h 45m 57s+06d 59m 11s+10.11.199Pisces
08 Feb 201723h 47m 28s+07d 04m 41s+10.01.186Pisces
09 Feb 201723h 48m 59s+07d 09m 59s+9.91.173Pisces
10 Feb 201723h 50m 30s+07d 15m 03s+9.81.160Pisces
11 Feb 201723h 52m 01s+07d 19m 49s+9.71.146Pisces
12 Feb 201723h 53m 31s+07d 24m 14s+9.61.131Pisces
13 Feb 201723h 55m 01s+07d 28m 14s+9.51.116Pisces
14 Feb 201723h 56m 29s+07d 31m 45s+9.31.101Pisces
15 Feb 201723h 57m 56s+07d 34m 41s+9.21.085Pisces
16 Feb 201723h 59m 21s+07d 36m 56s+9.11.069Pisces
17 Feb 201700h 00m 43s+07d 38m 25s+9.01.052Pisces
18 Feb 201700h 02m 03s+07d 38m 58s+8.91.034Pisces
19 Feb 201700h 03m 18s+07d 38m 27s+8.71.016Pisces
20 Feb 201700h 04m 30s+07d 36m 42s+8.60.998Pisces
21 Feb 201700h 05m 35s+07d 33m 30s+8.50.979Pisces
22 Feb 201700h 06m 34s+07d 28m 38s+8.30.960Pisces
23 Feb 201700h 07m 24s+07d 21m 49s+8.20.940Pisces
24 Feb 201700h 08m 06s+07d 12m 44s+8.00.919Pisces
25 Feb 201700h 08m 35s+07d 01m 02s+7.80.899Pisces
26 Feb 201700h 08m 51s+06d 46m 19s+7.70.878Pisces
27 Feb 201700h 08m 52s+06d 28m 06s+7.50.856Pisces
28 Feb 201700h 08m 33s+06d 05m 52s+7.30.835Pisces
01 Mar 201700h 07m 53s+05d 39m 04s+7.20.813Pisces
02 Mar 201700h 06m 49s+05d 07m 05s+7.00.792Pisces
03 Mar 201700h 05m 16s+04d 29m 21s+6.90.771Pisces
04 Mar 201700h 03m 12s+03d 45m 16s+6.70.751Pisces
05 Mar 201700h 00m 34s+02d 54m 25s+6.50.732Pisces
06 Mar 201723h 57m 21s+01d 56m 31s+6.40.714Pisces
07 Mar 201723h 53m 30s+00d 51m 38s+6.10.698Pisces
08 Mar 201723h 49m 04s-00d 19m 49s+6.00.684Pisces
09 Mar 201723h 44m 06s-01d 36m 54s+5.80.672Pisces
10 Mar 201723h 38m 40s-02d 58m 17s+5.70.664Pisces
11 Mar 201723h 32m 54s-04d 22m 09s+5.70.658Aquarius
12 Mar 201723h 26m 57s-05d 46m 33s+5.80.655Aquarius
13 Mar 201723h 20m 58s-07d 09m 25s+6.00.656Aquarius
14 Mar 201723h 15m 06s-08d 28m 56s+6.10.659Aquarius
15 Mar 201723h 09m 29s-09d 43m 40s+6.30.665Aquarius
16 Mar 201723h 04m 12s-10d 52m 34s+6.40.674Aquarius
17 Mar 201722h 59m 21s-11d 55m 04s+6.60.684Aquarius
18 Mar 201722h 54m 57s-12d 50m 60s+6.80.696Aquarius
19 Mar 201722h 51m 02s-13d 40m 29s+6.90.709Aquarius
20 Mar 201722h 47m 35s-14d 23m 51s+7.00.724Aquarius
21 Mar 201722h 44m 35s-15d 01m 34s+7.20.739Aquarius
22 Mar 201722h 42m 01s-15d 34m 09s+7.30.754Aquarius
23 Mar 201722h 39m 50s-16d 02m 08s+7.50.770Aquarius
24 Mar 201722h 38m 01s-16d 26m 03s+7.60.786Aquarius
25 Mar 201722h 36m 31s-16d 46m 23s+7.80.802Aquarius
26 Mar 201722h 35m 18s-17d 03m 33s+7.90.817Aquarius
27 Mar 201722h 34m 21s-17d 17m 59s+8.10.833Aquarius
28 Mar 201722h 33m 37s-17d 30m 02s+8.20.849Aquarius
29 Mar 201722h 33m 06s-17d 39m 59s+8.40.864Aquarius
30 Mar 201722h 32m 44s-17d 48m 07s+8.50.879Aquarius
31 Mar 201722h 32m 32s-17d 54m 41s+8.80.893Aquarius
01 Apr 201722h 32m 28s-17d 59m 52s+9.10.907Aquarius
02 Apr 201722h 32m 31s-18d 03m 53s+9.30.921Aquarius
03 Apr 201722h 32m 40s-18d 06m 51s+9.50.934Aquarius
04 Apr 201722h 32m 55s-18d 08m 55s+9.70.947Aquarius
05 Apr 201722h 33m 14s-18d 10m 12s+9.90.960Aquarius
06 Apr 201722h 33m 36s-18d 10m 48s+10.10.972Aquarius
07 Apr 201722h 34m 03s-18d 10m 50s+10.30.984Aquarius
08 Apr 201722h 34m 32s-18d 10m 21s+10.50.995Aquarius
09 Apr 201722h 35m 04s-18d 09m 26s+10.71.006Aquarius
10 Apr 201722h 35m 38s-18d 08m 08s+10.91.017Aquarius
11 Apr 201722h 36m 13s-18d 06m 31s+11.01.027Aquarius
12 Apr 201722h 36m 50s-18d 04m 38s+11.21.037Aquarius
13 Apr 201722h 37m 29s-18d 02m 32s+11.41.047Aquarius
14 Apr 201722h 38m 08s-18d 00m 14s+11.51.056Aquarius
15 Apr 201722h 38m 48s-17d 57m 47s+11.71.065Aquarius
16 Apr 201722h 39m 28s-17d 55m 13s+11.81.073Aquarius
17 Apr 201722h 40m 09s-17d 52m 33s+12.01.081Aquarius
18 Apr 201722h 40m 49s-17d 49m 49s+12.11.089Aquarius
19 Apr 201722h 41m 30s-17d 47m 02s+12.21.096Aquarius
20 Apr 201722h 42m 11s-17d 44m 14s+12.41.103Aquarius
21 Apr 201722h 42m 51s-17d 41m 26s+12.51.110Aquarius
22 Apr 201722h 43m 31s-17d 38m 38s+12.61.116Aquarius
23 Apr 201722h 44m 11s-17d 35m 52s+12.71.122Aquarius
24 Apr 201722h 44m 50s-17d 33m 09s+12.91.128Aquarius
25 Apr 201722h 45m 28s-17d 30m 29s+13.01.134Aquarius
26 Apr 201722h 46m 05s-17d 27m 54s+13.11.139Aquarius
27 Apr 201722h 46m 42s-17d 25m 23s+13.21.144Aquarius
28 Apr 201722h 47m 17s-17d 22m 58s+13.31.148Aquarius
29 Apr 201722h 47m 52s-17d 20m 39s+13.41.153Aquarius
30 Apr 201722h 48m 25s-17d 18m 26s+13.51.157Aquarius

Sky Highlights - June 2017

Saturn
Saturn reaches opposition on June 15

The Planets
This Month's Guide

Algol Minima
Algol eclipse dates and times for June

Northern Hemisphere
Evening
Southwest:- Jupiter (mag. -2.2)
Southeast:- Saturn (mag. 0.0)
Midnight
West:- Jupiter
South:- Saturn
Morning
Southwest:- Saturn
Southeast:- Neptune (mag. +7.9)
East:- Venus (mag. -4.3), Uranus (mag. +5.9)

Southern Hemisphere
Evening
North:- Jupiter
East:- Saturn
Midnight
West:- Jupiter
North:- Saturn
Morning
West:- Saturn
Northeast:- Neptune
East:- Venus, Uranus, Mercury (first half of month (mag. -0.4 to -1.2)

Deep Sky

Small telescopes:-
Messier 13 - M13 - Great Hercules Globular Cluster
Messier 92 - M92 - Globular Cluster
Messier 11 - M11 - The Wild Duck Cluster (Open Cluster)
Messier 7 - M7 - The Ptolemy Cluster (Open Cluster)
Messier 6 - M6 - The Butterfly Cluster (Open Cluster)
Messier 4 - M4 - Globular Cluster
Messier 8 - M8 - Lagoon Nebula (Emission Nebula)
Messier 16 - M16 - Eagle Nebula (Emission Nebula with Open Cluster)
Messier 20 - M20 - Trifid Nebula (Emission and Reflection Nebula)

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