The night sky in January 2021

posted 30 Dec 2020, 12:54 by Pete Collins   [ updated 31 Dec 2020, 04:17 ]
by Anne Holt

Sunrise     1st:   08.24       31st:   07.55
Sunset      1st:   16.00       31st:   16.50

Astronomical darkness
1st:   18.11 to 06.14       31st:  18.51 to 05.52

Earth is at perihelion on 2nd, when it will be 0.98 AU from the Sun. Its orbit is almost circular so the apparent size of the Sun doesn't differ by much,  it will appear only 5% larger than at aphelion.

New Moon:  13th at 05.02      Full Moon:  28th at 19.18

Lunar perigee:  9th at 15.36  (367389 Km)  On this day the Moon will be a thin waning crescent with a diameter of 32.51 arcminutes.

Lunar apogee:  21st at 13.10  (464360 Km)  waxing gibbous phase, diameter 29.32 arcminutes.

The January full Moon is most commonly referred to as the Wolf Moon, because the animals howl more at this time.  It was thought that this was because they were hungry but it is now believed to be the time when they are marking their territory and locating other pack members to gather together to go hunting. 
Other names are the Moon after Yule, the Old Moon and the Snow Moon. It's the Colonial American Snow Moon, the Chinese Holiday Moon and the Celtic Quiet Moon or Stay Home Moon - very appropriate right now!  The neo pagan name is the Ice Moon and the Medieval English also called it the Wolf Moon.  As always there are many indigenous American names - the Cherokee Cold Moon, the Choctaw Cooking Moon and the Dakota Sioux Moon of the Terrible (didn't say terrible what).  The best name this month is from the Oneida tribe - the Someone's Ears are Freezing Moon.


Highlights

After the excitement of December's Grand Conjunction there's not a lot to look forward to this month.  We still have plenty of astro darkness - a few minutes over 12 hours on 1st and an hour less by the end of January. The naked eye planets are past their best now, Venus is hardly visible in the morning sky  and Jupiter and Saturn are very low in the evening twilight as they approach solar conjunction near the end of the month. As they get lower, Mercury gets higher, towards the end of January it will be visible to observers with a clear SW horizon. Mars continues to fade but is still quite prominent in the evening sky. The one major meteor shower will be marred by the presence of the gibbous Moon and no bright comets are expected.
However January can be a very good time for naked eye observing.  On a cold, clear night the sky, particularly the region of the Winter Hexagon, is a magnificent sight especially from a dark sky area.

Constellations

There isn't much change in the prominent constellations since December, just that everything rises, or sets, a couple of hours earlier. Orion is now well above the horizon by 8pm at the start of the month, with Sirius rising at this time.  By month end, Sirius will rise at about 6pm.  Auriga, Gemini and Cassiopeia are all high in the sky. The Summer Triangle is now setting earlier as the Winter Hexagon rises. Taurus and the Pleiades are still very prominent and the spring constellation of Leo is above the south eastern horizon by 9pm.

Planets

Mercury:  in Sagittarius, mag -1.0
Not visible in early January.  On 1st it sets 20 minutes after the Sun and appears only 7 degrees from it. It moves into Capricorn on 9th when it is only 1 degree above the horizon at dusk, setting at 16.58.  Over the next few days it is close to Jupiter and Saturn, on 10th it is lower than both, forming an approximately equilateral triangle, but moves higher as the gas giants get lower in the evening twilight.  By 11th it is slightly higher than Saturn and on 13th they are in a line wih Mercury highest, Jupiter below it slightly to the right and Saturn, the faintest of the three, close to the horizon. The following day the thin crescent Moon is to the left of the trio. By 22nd, now at mag -0.8, Mercury should be easier to spot at 8 degrees above the SW horizon as the sky darkens, setting at 18.10.  It is at greatest eastern elongation on 24th, separated from the Sun by 18.6 degrees, but still only 9 degrees in the SW at dusk, setting at 18.18. It is harder to see in the last week of the month as it fades rapidly as it gets lower in the evening sky.  By 31st it is down to mag 0.7 and only 7 degrees above the horizon at dusk.

Venus:  in Ophiuchus, mag -3.9
Not easy to see now, still bright but very low in the morning sky. On 1st it rises at 06.52 and only gets to 6 degrees above the horizon by dawn.  This is down to 4 degrees on 6th, when it moves into Sagittarius. On 11th, the thin crescent Moon passes 1 degree 29' south of the planet at 20.11 while they are both below the horizon.  On the morning of 11th the Moon rises at 06.27, Venus at 07.13, they will be separated by just over 5 degrees but Venus will be only 3 degrees above the horizon when the sky brightens.  By the last week in January it fails to clear the horizon by dawn.

Mars:  in Pisces, mag -0.2
Still quite bright and high in the sky in the early part of the night.  On 1st it should become visible around 16.30 as the sky darkens, 38 degrees in the SE,  reaching its highest point, 47 degrees in the south, at 19.02.  By 01.00 it is down to 9 degrees in the west, setting at 02.13.  It moves into Aries on 6th, now down to mag -0.1 and culminating at 18.51 when it is at 48 degrees. On the evening of 20th the almost 1st quarter Moon is close to the planet, about 7 degrees to the SW as they set soon after midnight.  The following evening the Moon is ESE of Mars, separated by 6 degrees 25' as they become visible around 17.10.  On this night Mars is only 1 degree 43' north of the much fainter Uranus. By 31st Mars has faded to mag 0.4, visible from 17.30 and culminating half an hour later at 52 degrees, setting at 01.44.

Jupiter:  in Capricorn, Mag -2.0
Now very low in the evening twilight but still bright enough to be seen in early January.  On 1st it is 8 degrees above the SW horizon at 16.30, setting at 17.50. A week later it is only at 6 degrees as the sky darkens and sets at 17.32.  On 9th Mercury is 3 degrees 10' to the SW with Saturn between them.  By 20th Jupiter is no longer visible as it appears only 7 degrees from the Sun.  It is at solar conjunction on 29th, when it passes 31' south of the Sun at 01.44. On 31st it is only 1 degree from the Sun, rising a minute after it.

Saturn:  in Capricorn, mag 0.6
On 1st it is still only 1 degree 20' from Jupiter but is much harder to see as it is now lower and much fainter at dusk, setting at 17.44.  By 8th this is down to 2 degrees and on 17th it appears separated from the Sun by only 6 degrees. It reaches solar conjunction on 24th, passing 24' to the south.  By 31st it is theoretically a morning object but rises just 10 minutes before the Sun, apparent separation 6 degrees.

Uranus:  in Aries, mag 5.7
Still high in the sky for much of the night. On 1st it should be visible from around 17.30 at 42 degrees in the SE, culminating at 19.40, when it reaches 49 degrees in the south. It will remain visible until shortly after midnight when it is down to 21 degrees in the west, setting at 03.03.  In the first half of January it appears to be moving from east to west against the background stars, known as retrograde motion, on 16th it apears to stand still for a short while before starting to move in the opposite direction - west to east, prograde motion.  On 20th and 21st Mars passes north of Uranus, closest on the night of 20th when they are separated by 1 degree 37'.  On 21st at 23.34 they are in conjunction, with Mars 1 degree 43' directly north of the distant ice giant.   By this time they are quite low in the western sky, only 21 degrees.  These two nights are a good time to try to spot Uranus through binoculars, they will be visible in the same field of view of a pair of 20x50s.  It will probably be difficult to see Uranus with the naked eye around this time, even from a very dark sky site, because of the proximity of the gibbous Moon - SW of the planets on 20th and SE on 21st. On 31st Uranus culminates at 17.42 in nautical twilight, becoming visible, 42 degrees in the south, about half an hour later as the sky darkens.  It remains reasonably high until 22.30 and sets at 01.05.

Neptune:  in Aquarius, mag 7.8
On 1st it should be observable from 17.30 when it will be at 29 degrees in the south, having culminated at 16.42. By 19.20 it will be very low in the west, setting at 22.15. On 10th at 16.47 it is in conjunction with dwarf planet Ceres but the two aren't very close - Neptune passes 8 degrees 37' to the north.  It will be at 27 degrees in the south as the sky darkens around 17.30.  Ceres, fainter and much lower will be a more difficult target.  By the last week in January Neptune is very low as the sky darkens, only 21 degrees on 23rd and 17 degrees on 31st, when it sets at 21.21.

Dwarf Planets

Ceres:  in Aquarius, mag 9.4
Low in the evening sky this month.  On 1st it is only 20 degrees above the horizon as the sky darkens, setting at 21.06.  On 31st it is 19 degrees at dusk and sets at 20.13.

The rest are much fainter, orbiting in the distant Kuiper Belt and therefore out of reach of all but the very best astrophotographers.  They have orbits which are highly inclined to the plane of the Solar System so aren't confined to the ecliptic band of the sky.

Pluto:  in Sagittarius, mag 15
Appears only 13 degrees from the Sun on 1st and moves even closer during the first half of January.  On 14th it is at solar conjunction, passing 1 degree 12' south of the Sun.  On 31st it rises only half an hour before the Sun, apparent separation 15 degrees.

Haumea:  in Bootes, mag 17.4
Discovered in 2004 and named after the Hawaiian goddess of fertility.  It has two small moons, found the following year, which were given the names of her daughters Hi'iaka and Namaka.
Well positioned for imaging in the morning sky.  On 1st it is at 21 degrees by 3am and reaches 49 degrees in the SE before the sky gets too bright a little before 07.00.  On 31st it gets to 21 degrees in the east by 01.00 and is at its highest point, 51 degrees in the south, at 05.55, only a couple of minutes after the end of astro darkness.

Makemake:  in Coma Berenices, mag 17.2
First observed in March 2005 and given the nickname Easterbunny before being officially named Haumea after the Easter Island Rapa Nui people's creator of humanity and god of fertility. It has one tiny moon which still hasn't been given a mythological name and is referred to as MK2.
On 1st it reaches 21 degrees in the east soon after 1am and culminates,  59 degrees in the south, at 06.40 a few minutes after the sky begins to brighten. On 31st it will be at 21 degrees in the east at 23.00, culminating at 04.42 when it is 59 degrees above the southern horizon and remaining high until dawn.

Eris:  in Cetus, mag 18.8
Appropriately named after the goddess of discord, her moon is Dysnomia - called after her daughter, not the condition of being unable to recall words. 
High in the sky in the early part of the night but much too faint for most amateurs to attempt.  On 1st it is at 31 degrees in the east as the sky darkens and reaches 34 degrees in the south a few minutes after 19.00, down to 22 degrees in the SW by 22.19.  On 31st it culminates only 20 minutes after sunset, is at 31 degrees in the south as astro twilight begins and is high enough for imaging for just a couple of hours.

There are a couple of reasonably bright asteroids at opposition in January

15 Eunomia:  in Cancer, mag 8.4
At opposition on 21st, when it is high in the sky from 19.16 until dawn, reaching its highest point, 53 degrees above the southern horizon, at 00.23

14 Irene:  in Cancer, mag 9.3
Opposition on 24th, when it is high from 18.30 to 06.05.  Highest point, 65 degrees in the south, at 00.37

Comets

Nothing spectacular predicted for January.

141P/Machholz: in Aquarius, mag 9.8
On 1st it culminates a few minutes after sunset, becoming visible, 27 degrees above the southern horizon, at 17.45 and remaining reasonably high for just over an hour.  It moves into Cetus on 11th, probably slightly fainter at mag 10.2.  On 31st, predicted mag now 11.8, it should become visible (through a scope) at 18.13, when it is 32 degrees in the south, remaining quite high until just before 21.00, setting at 23.45.

C/2020 M3 (ATLAS):  in Auriga, mag 11.0
Circumpolar, high for most of the night, but faint - and fading. On 1st it is at 42 degrees in the NE as the sky fades, culminating,  82 degrees in the south, at 22.37. By dawn it is down to 21 degrees in the NW.  It is moving northwards, passing to the right of Capella during the first few days in January, then veering across the top of Auriga towards Gemini. (eastwards in the early evening sky). On 31st, estimated mag now 13.3, it is 63 degrees in the east soon after 18.00, 85 degrees in the south at 20.58 and 17 degrees NW at 06.26.

C/2020 S3 (Erasmus): in Scutum, mag 8.2
On 1st it rises 40 minutes before the Sun and appears separated by only 7 degrees.  It moves into Sagittarius on 2nd, Aquila on 12th, Capricorn on 15th, back into Aquila on 21st and into Aquarius on 23rd.  During this time its separation from the Sun increases but it also fades significantly. On 31st it is 12 degrees from the Sun but its predicted mag is only 11.8.

For more information on all Solar System objects, including co-ordinates and position charts, see:
https://in-the-sky.org  (this is the one that I find most useful, it has all the information you could ever need, easily accessible)

www.cometwatch.co.uk appears to be dormant once again. the current comets page hasn't been updated since mid November, everything else is even more out of date.

Meteor Showers

One major shower this month, marred this year by moonlight, daylight - and probably clouds.

Quadrantids:  active Dec 28th to Jan 12th, has a short peak of around 6 hours centred on 14.28 on 3rd.  The circumpolar radiant is highest in daylight, so the shower is best seen before dawn on that day.  ZHR varies according to source, the highest given is around 100 but, as the peak is in daylight, we are unlikely to see more than 25 per hour in darkness.  These are medium speed meteors, mainly of only medium brightness, so they will be badly affected by the presence of the gibbous Moon, shining at mag -12.6.  However, on the plus side, the shower does usually include some bright meteors, and maybe even a few fireballs, which should be visible in the bright sky. The shower is named after the short lived constellation Quadrans Muralis, the wall quadrant, created in 1795 by French astronomer Jerome Lalande who used one of these to measure star positions.  When the IAU divided the sky into 88 officialy recognised constellations in 1922 it was not included, the area which it covered is now in northern Bootes.  There are no records of this shower prior to 1815, it is thought that the dust stream was shifted by the gravitational pull of Jupiter, so Earth has only passed through it since the early 19th century.  The parent body isn't known for sure, the most likely candidate is asteroid 2003 EH1, which could be a part of the defunct comet C/1490 Y1, observed by Chinese and Korean astronomers in 1490 but which disintegrated about 100 years later. 

Gamma Ursa Minorids:  active Jan 10th to 22nd, peak 19th/20th. ZHR 3.
Not much is known about this weak shower of slow moving meteors, best seen just before dawn.

Kappa Cancrids.  There has been little or no activity from these in recent years.  The radiant is close to that of the ANT (see below) but these are much faster moving.  Peak given as Jan 10th, so one or two meteors might possibly be seen around that date.

Antihelion Source (ANT) is active in January.  These are meteors which can't be attributed to a particular shower, as there are a number of very weak ones having a radiant on the ecliptic, opposite the position of the Sun. It starts January in SE Gemini then moves through Cancer during the month.  These slow moving meteors have a ZHR of 4 under ideal conditions.





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