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Comet Wirtanen

by David Nakamoto

Nov 22nd, 2018

Comet Wirtanen, periodic comet 46P, will have a once in a lifetime passage close to earth in December of 2018.  This is due to two events, a few days apart, that will make the comet brighter than it usually is.

December 12th -- Wirtanen will be closest to the Sun, perihelion.  It will be as bright as it can get, if it follows its behavior during past perihelion passages.

December 16th -- Wirtanen will be closest to the earth, only 11.5 million km or 7.1 million miles away.  This will also contribute to making it as bright as it can get, for observers on earth anyways.

This coincidence of a perihelion passage followed by a close approach mimics Mars’ opposition in July of this year.  Now when Mars did this, a global dust storm conspired to make Mars' globe a bland featureless disk.  However, we want Wirtanen to produce lots of dust and gas, which will make it reflect more sunlight, so the comet will become bright.  Some estimates predict Wirtanen might reach magnitude 4.  But comets are notoriously unpredictable, so it might become even brighter, or it might even fade.  Since no one knows which way it goes, this is not a comet to miss.  No other comet is predicted to be brighter than 8th mag in 2019.

 

Since no one knows what will happen, I urge observers to look frequently and often as the comet goes from the southern skies to the north.  It actually becomes visible all night as it passes by the earth.  Remember, nothing in the sky waits for anyone.  Small scopes, binoculars, anything that is easy to use at a moment’s notice is better than nothing, so make the most of every chance you can get.

Below is a star chart showing the path of the comet.  Notice that at perihelion Dec 12th and closest approach on the 16th, the comet is fairly high in the sky just west of Taurus the Bull.  Late December and early January it passes Lynx and heads towares Ursa Major, going circumpolar in the process and so appearing all night.

Comet Wirtanen

Based to the light curve made up of observed magnitudes, Wirtanen is behaving according to predictions, so 4th mag appears to be possible.

What will we see ?  Well, Wirtanen will travel alongside earth during the close encounter, and going in the same direction.  This means the passage won't be a quick one, but will last for several weeks.  Since the tails point away from the Sun, and the comet is almost opposite the Sun during the encounter, we’re looking at the part of the comet pointed towards the Sun and earth, with the tails trailing away from the earth.  This might mean the dust tail might be short, and the plasma tail even shorter.  On the other hand, before closest approach, we’ll be looking “down” on the comet, and after we’ll be “below” it looking “up” at it.  Both tails might be long at these times.  The only way to be sure is to look at Wirtanen with anything you have.

The ephemeris below was generated by <in-the-sky.org>.  As with all comet magnitude estimates, your mileage may vary, but LOOK !

Happy Hunting !

David Nakamoto can be reached at This email address is being protected from spambots. You need JavaScript enabled to view it..

Ephemeris for 46P/Wirtanen

Date

Age of

Right

Declination

Rise

Culm

Set

Approx

Constellation

 

   

Moon

Ascension

 

     

Mag.

 

2018

Dec

01

24 days

02h25m08s

-20°16'38"

16:29

21:34

02:43

6.0

Cetus

2018

Dec

03

25 days

02h28m16s

-18°42'51"

16:23

21:33

02:47

5.9

Cetus

2018

Dec

04

26 days

02h31m39s

-16°59'45"

16:17

21:32

02:51

5.8

Cetus

2018

Dec

05

27 days

02h35m19s

-15°06'24"

16:11

21:32

02:57

5.7

Cetus

2018

Dec

06

28 days

02h39m18s

-13°01'53"

16:05

21:32

03:03

5.6

Cetus

2018

Dec

07

29 days

02h43m38s

-10°45'15"

15:59

21:32

03:10

5.5

Cetus

2018

Dec

08

00 days

02h48m19s

-08°15'40"

15:53

21:33

03:17

5.4

Eridanus

2018

Dec

09

01 days

02h53m24s

-05°32'23"

15:47

21:34

03:26

5.3

Eridanus

2018

Dec

10

02 days

02h58m55s

-02°34'54"

15:40

21:36

03:35

5.2

Eridanus

2018

Dec

11

03 days

03h04m53s

+00°37'01"

15:33

21:38

03:46

5.1

Cetus

2018

Dec

12

04 days

03h11m22s

+04°02'59"

15:27

21:40

03:58

5.0

Cetus

2018

Dec

13

05 days

03h18m23s

+07°42'03"

15:20

21:43

04:11

4.9

Cetus

2018

Dec

14

06 days

03h25m58s

+11°32'31"

15:12

21:47

04:26

4.9

Taurus

2018

Dec

15

06 days

03h34m10s

+15°31'52"

15:05

21:51

04:42

4.8

Taurus

2018

Dec

16

07 days

03h43m01s

+19°36'45"

14:57

21:56

04:59

4.8

Taurus

2018

Dec

17

08 days

03h52m31s

+23°43'22"

14:49

22:02

05:18

4.8

Taurus

2018

Dec

18

09 days

04h02m44s

+27°47'22"

14:41

22:08

05:39

4.8

Taurus

2018

Dec

19

10 days

04h13m38s

+31°44'37"

14:32

22:15

06:02

4.8

Perseus

2018

Dec

20

11 days

04h25m13s

+35°31'05"

14:23

22:23

06:26

4.9

Perseus

2018

Dec

21

12 days

04h37m29s

+39°03'39"

14:13

22:31

06:53

4.9

Perseus

2018

Dec

22

13 days

04h50m21s

+42°19'47"

14:02

22:40

07:21

5.0

Auriga

2018

Dec

23

15 days

05h03m47s

+45°17'53"

13:51

22:49

07:52

5.1

Auriga

2018

Dec

24

16 days

05h17m41s

+47°57'13"

13:38

22:59

08:24

5.2

Auriga

2018

Dec

25

17 days

05h31m54s

+50°17'47"

13:23

23:09

09:00

5.3

Auriga

2018

Dec

26

18 days

05h46m20s

+52°20'06"

13:04

23:20

09:39

5.4

Auriga

2018

Dec

27

20 days

06h15m14s

+55°34'09"

Circumpolar

5.6

Auriga

2018

Dec

29

21 days

06h29m24s

+56°48'36"

Circumpolar

5.8

Lynx

2018

Dec

30

22 days

06h43m12s

+57°49'59"

Circumpolar

5.9

Lynx

2018

Dec

31

23 days

06h56m29s

+58°39'49"

Circumpolar

6.0

Lynx

2019

Jan

01

24 days

07h09m13s

+59°19'34"

Circumpolar

6.1

Lynx

2019

Jan

02

25 days

07h21m16s

+59°50'33"

Circumpolar

6.2

Lynx

2019

Jan

03

26 days

07h32m38s

+60°14'01"

Circumpolar

6.4

Camelopardalis

2019

Jan

04

27 days

07h43m17s

+60°31'05"

Circumpolar

6.5

Camelopardalis

2019

Jan

05

28 days

07h53m12s

+60°42'44"

Circumpolar

6.6

Camelopardalis

2019

Jan

06

29 days

08h02m23s

+60°49'47"

Circumpolar

6.7

Camelopardalis

2019

Jan

07

00 days

08h10m53s

+60°52'58"

Circumpolar

6.8

Ursa Major

2019

Jan

08

01 days

08h18m43s

+60°52'56"

Circumpolar

6.9

Ursa Major

2019

Jan

09

02 days

08h25m55s

+60°50'09"

Circumpolar

7.0

Ursa Major

2019

Jan

10

03 days

08h32m31s

+60°45'06"

Circumpolar

7.1

Ursa Major

2019

Jan

11

04 days

08h38m33s

+60°38'08"

Circumpolar

7.3

Ursa Major

2019

Jan

12

05 days

08h44m05s

+60°29'33"

Circumpolar

7.4

Ursa Major

2019

Jan

13

06 days

08h49m08s

+60°19'36"

Circumpolar

7.5

Ursa Major

2019

Jan

14

07 days

08h53m44s

+60°08'31"

Circumpolar

7.6

Ursa Major

2019

Jan

15

08 days

08h57m56s

+59°56'28"

Circumpolar

7.7

Ursa Major

2019

Jan

16

09 days

09h01m45s

+59°43'35"

Circumpolar

7.8

Ursa Major

2019

Jan

17

10 days

09h05m14s

+59°30'01"

Circumpolar

7.9

Ursa Major

2019

Jan

18

11 days

09h08m25s

+59°15'49"

Circumpolar

8.0

Ursa Major

2019

Jan

19

12 days

09h11m18s

+59°01'06"

Circumpolar

8.1

Ursa Major

2019

Jan

20

13 days

09h13m55s

+58°45'56"

Circumpolar

8.2

Ursa Major

2019

Jan

21

14 days

09h16m17s

+58°30'21"

Circumpolar

8.3

 

2019

Jan

22

16 days

09h20m23s

+57°58'10"

Circumpolar

8.5

Ursa Major

2019

Jan

24

17 days

09h22m09s

+57°41'38"

Circumpolar

8.6

Ursa Major

2019

Jan

25

19 days

09h23m45s

+57°24'48"

Circumpolar

8.7

Ursa Major

2019

Jan

26

20 days

09h25m11s

+57°07'45"

Circumpolar

8.8

Ursa Major

2019

Jan

27

21 days

09h26m29s

+56°50'27"

Circumpolar

8.9

Ursa Major

2019

Jan

28

22 days

09h27m40s

+56°32'55"

Circumpolar

9.0

Ursa Major

2019

Jan

29

23 days

09h28m43s

+56°15'11"

Circumpolar

9.0

Ursa Major

2019

Jan

30

24 days

09h29m40s

+55°57'13"

Circumpolar

9.1

Ursa Major

2019

Jan

31

25 days

09h30m31s

+55°39'04"

Circumpolar

9.2

Ursa Major

2019

Feb

01

26 days

09h31m17s

+55°20'42"

Circumpolar

9.3

Ursa Major

2019

Feb

02

26 days

09h31m59s

+55°02'10"

13:07

00:39

12:08

9.4

Ursa Major

2019

Feb

03

27 days

09h32m36s

+54°43'26"

13:19

00:36

11:50

9.5

Ursa Major

2019

Feb

04

28 days

09h33m10s

+54°24'32"

13:27

00:33

11:35

9.6

Ursa Major

2019

Feb

05

00 days

09h33m41s

+54°05'27"

13:33

00:29

11:22

9.7

Ursa Major

2019

Feb

06

00 days

09h34m09s

+53°46'12"

13:38

00:26

11:10

9.8

Ursa Major

2019

Feb

07

01 days

09h34m34s

+53°26'48"

13:42

00:22

10:59

9.9

Ursa Major

2019

Feb

08

02 days

09h34m58s

+53°07'15"

13:45

00:19

10:49

10.0

Ursa Major

2019

Feb

09

03 days

09h35m20s

+52°47'33"

13:48

00:15

10:39

10.1

Ursa Major

2019

Feb

10

04 days

09h35m40s

+52°27'44"

13:50

00:12

10:29

10.2

Ursa Major

2019

Feb

11

05 days

09h36m00s

+52°07'46"

13:52

00:08

10:20

10.2

Ursa Major

2019

Feb

12

06 days

09h36m18s

+51°47'42"

13:53

00:04

10:11

10.3

Ursa Major

2019

Feb

13

07 days

09h36m35s

+51°27'31"

13:55

23:57

10:03

10.4

Ursa Major

2019

Feb

14

08 days

09h36m52s

+51°07'14"

13:56

23:53

09:54

10.5

Ursa Major

2019

Feb

15

09 days

09h37m09s

+50°46'52"

13:57

23:50

09:46

10.6

Ursa Major

2019

Feb

16

10 days

09h37m25s

+50°26'25"

13:57

23:46

09:38

10.7

Ursa Major