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Night sky, December 2020: What you can see this month [maps]

A clear night sky offers an ever-changing display of fascinating objects to see — stars, constellations, and bright planets, often the moon, and sometimes special events like meteor showers. Observing the night sky can be done with no special equipment, although a sky map can be very useful. Binoculars or a good beginner telescope will enhance some experiences and bring some otherwise invisible objects into view. You can also use astronomy apps and software to make your observing easier, and use our Satellite Tracker page powered by N2YO.com to find out when to see the International Space Station and other satellites. Below, find out what's up in the night sky tonight (Planets Visible Now, Moon Phases, Observing Highlights This Month) plus other resources (Skywatching Terms, Night Sky Observing Tips and Further Reading).

The night sky is more than just the moon and stars, if you know when and where to look. (Image credit: Karl Tate/SPACE.com)

Monthly skywatching information is provided to Space.com by Chris Vaughan of Starry Night Education, the leader in space science curriculum solutions. Follow Starry Night on Twitter @StarryNightEdu and Chris at @Astrogeoguy.

Editor's note: If you have an amazing skywatching photo you'd like to share for a possible story or image gallery, you can send images and comments in to spacephotos@futurenet.com.

Night Sky Guides:

Calendar of Observing Highlights

Tuesday, December 1 — Bright moon crosses Messier 35 (overnight)

(Image credit: Starry Night)

Between Tuesday evening, Dec. 1 and the following morning, observers in most of North America will see the orbital motion (green line) of the waning gibbous moon carry it in front of a large open star cluster known as Messier 35, or the Shoe-Buckle Cluster, in Gemini. While the moon climbs the eastern sky during Tuesday evening, it will be slowly approaching the cluster from the celestial west. To best see Messier 35's stars at that time, wait until they are higher in mid-evening, and then hide the bright moon beyond the upper right edge of your binoculars (red circle). The moon will obscure all or part of the cluster for about 2 hours centered on 3:40 a.m. Eastern Standard Time (or 8:40 GMT), and then it will depart from the cluster's upper left (or celestial east) edge while both objects descend in the western sky.

Friday, December 4 — Moon and the Beehive (overnight)

(Image credit: Starry Night)

When the waning gibbous moon rises in the eastern sky in late evening on Friday, Dec. 4, it will positioned only two finger widths to the left (or 2 degrees to the celestial north) of the large open star cluster known as the Beehive, or Messier 44, in Cancer. The cluster, which contains at least 1000 stars, extends for two full moon diameters across the sky. The moon and the cluster will fit together in the field of view of binoculars (red circle). During the rest of the night the moon's eastward orbital motion (green line) will carry it farther from the Beehive. To best see the cluster's stars, hide the bright moon just outside the left edge of your binoculars' field of view.

Monday, December 7 — Moon near asteroid Vesta (pre-dawn) 

(Image credit: Starry Night)

High in the southern pre-dawn sky on Monday, Dec. 7, the waning gibbous moon will be positioned a palm's width to the upper right (or 6 degrees to the celestial west) of the magnitude 7.55 main belt asteroid Vesta in the constellation of Leo, the Lion. For about an hour centered on 21:00 GMT, observers in most of eastern and northern Europe, parts of Russia and China, Japan, northern Philippines, and Micronesia can see the moon cross in front of (or occult) Vesta.

Tuesday, December 8 — Last quarter moon (at 0:37 GMT)

(Image credit: Starry Night)

When it reaches its last quarter phase at 0:37 GMT on Tuesday, Dec. 8 (or 7:37 p.m. EST on Monday, Dec. 7), the moon will rise at about midnight, and then remain visible in the southern sky all morning. At last quarter, the moon is illuminated on its western side, towards the pre-dawn sun. Last quarter moons are positioned ahead of the Earth in our trip around the sun. About 3½ hours later, Earth will occupy that same location in space. The week of moonless evening skies that follow last quarter will be ideal for observing deep sky targets.

Saturday, December 12 — Old moon near Venus (pre-dawn)

(Image credit: Starry Night)

In the southeastern pre-dawn sky on Saturday, Dec. 12, the delicate sliver of the old crescent moon will be positioned several finger widths to the upper right (or 4.5 degrees to the celestial west) of bright Venus. The moon and Venus will fit together within the field of binoculars (red circle). For several hours following sunrise, sharp eyes can look for Venus' bright point of light shining a short distance to the left of the moon in daylight. At approximately 22:00 GMT on Dec. 12, the moon will occult Venus for observers in easternmost Russia, Hawaii, and western North America.

Monday, December 14 — Geminids meteor shower peak (midnight to dawn)

(Image credit: Starry Night)

The Geminids meteor shower, usually one of the most spectacular showers of the year, runs from Dec. 4 to Dec. 17 annually. In 2020, the shower will peak before dawn on Monday, Dec. 14. Geminids meteors are often bright, intensely colored, and slower moving than average because they are produced by particles dropped by an asteroid designated 3200 Phaethon. The best time to watch for Geminids will be from full darkness on Sunday until dawn on Monday morning. At about 2 a.m. local time, the sky overhead will be pointed toward the densest part of the debris field, and up to 120 meteors per hour are possible under dark sky conditions. True Geminids will appear to radiate from a position in the sky above the bright stars Castor and Pollux, but the meteors can appear anywhere in the sky. A new moon on the peak night should deliver a terrific shower for 2020.

Monday, December 14 — New Moon and total solar eclipse (at 16:16 GMT)

(Image credit: Starry Night)

At its new phase, the moon is travelling between Earth and the sun. Since sunlight can only reach the far side of the moon, and the moon is in the same region of the sky as the sun, the moon becomes completely hidden from view for about a day. This new moon will also produce a total solar eclipse visible inside a narrow track from the South Pacific Ocean, across southern South America, and ending at sunset in the South Atlantic Ocean. The areas of partial eclipse encompass about 2/3 of South America and much of the oceans to either side. The moon's shadow will first contact Earth at 14:33 GMT in the Pacific Ocean about 2425 miles (3900 km) southeast of Hawaii. During the 97 minutes required for the moon's umbra to reach landfall on the coast of Chile at 16:00 GMT, the path of totality will widen to 56 miles (90 km). There, the sun will be at an altitude of 71°, and totality will last 2 minutes 8 seconds. Greatest eclipse will occur in Argentina at 16:13:29 GMT, with a totality of 2 minutes 10 seconds. The rest of the total eclipse will not see landfall, leaving the Earth at 17:54 GMT just 225 miles (360 km) west of the coast of Namibia. Except during totality, proper solar filters will be required to view this eclipse.

Tuesday, December 15 — Jupiter and Saturn pass Messier 75 (early evening)

(Image credit: Starry Night)

As the gas giant planets prepare for their Great Conjunction on Dec. 21, they will pass close to a magnitude 9.2 globular star cluster designated as Messier 75 (or M75) and NGC 6864. On Tuesday, Dec. 15 and the surrounding evenings, Jupiter and Saturn will sit approximately a finger's width to the upper right (or 1.25 degrees to the celestial north) of Messier 75 — allowing all three objects to appear together in the field of view of a backyard telescope at low magnification (red circle). To better see the dim, fuzzy cluster, try to view the trio as soon as the sky darkens, when they are higher in the sky. The meet-up will especially favor observers at southerly latitudes.

Wednesday, December 16 — Young moon below Jupiter and Saturn (after sunset)

(Image credit: Starry Night)

Look low in the southwestern sky immediately after sunset on Wednesday, Dec. 16, for the young crescent moon sitting a slim palm's width below the bright, close-together duo of Jupiter and Saturn. The grouping will make a wonderful photo opportunity when composed with some interesting foreground scenery. The fun continues the following day when…

Thursday, December 17 — Crescent moon beside Jupiter and Saturn (early evening)

(Image credit: Starry Night)

The moon's monthly visit with the gas giant planets Jupiter and Saturn will continue after sunset on Thursday, Dec. 17. After 24 hours, the moon's orbital motion will carry it a fist's diameter to the upper left (or 9.5 degrees to the celestial southeast) of Jupiter and Saturn. The trio will make a wonderful photo opportunity when composed with some interesting foreground scenery - until the two close-together planets set at about 7:15 p.m. local time. The Moon will set 30 minutes after them. 

Monday, December 21 — Northern winter solstice (at 10:02 GMT)

(Image credit: Starry Night)

Winter in the Northern Hemisphere will officially commence on Monday, Dec. 21 at 10:02 GMT (or 5:02 a.m. EST and 2:02 a.m. PST). At that time the sun will reach the solstice — its southernmost declination for the year, resulting in the lowest noonday sun, the shortest amount of daylight of the year for the Northern Hemisphere, and the longest amount for the Southern Hemisphere. After the December solstice, the daylight hours will begin to increase for the Northern Hemisphere.

Monday, December 21 — Great Conjunction of Jupiter and Saturn (after sunset)

(Image credit: Starry Night)

In the southwestern sky after sunset on Monday, Dec. 21, Jupiter's faster orbital motion will bring it within 0.1 degrees of slower Saturn, causing the two planets to appear, to the unaided eye, as a single bright object. The two planets haven't been as close together since Galileo was using his spyglass in 1623 — and they won't meet so closely again until 2080. The two planets will easily appear together in the field of view of a backyard telescope at high magnification (inset with red circle). You'll need to start observing them as soon as you can find them in the darkening sky, because they will set in the west at about 7 pm local time. Don't wait until Dec. 21 to view this spectacular conjunction. They're already a pretty pair, and they'll still be telescope-close for more than a week on either side of that date.

Monday, December 21 — First quarter Moon (at 6:41 p.m. EST)

(Image credit: Starry Night)

When the moon completes the first quarter of its orbit around Earth at 6:41 p.m. EST (or 23:41 GMT) on Monday, Dec. 21, the relative positions of the Earth, sun, and moon will cause us to see it half-illuminated — on its eastern side. At first quarter, the moon always rises around noon and sets around midnight, so it is also visible in the afternoon daytime sky. The evenings surrounding first quarter are the best for seeing the lunar terrain when it is dramatically lit by low-angle sunlight. 

Monday, December 21 — Lunar X (starting around 7 p.m. PST)

(Image credit: Starry Night)

Several times a year, for a few hours near its first quarter phase, a feature on the moon called the Lunar X becomes visible in strong binoculars and backyard telescopes. When the rims of the craters Purbach, la Caille, and Blanchinus are illuminated from a particular angle of sunlight, they form a small, but very obvious X-shape. The Lunar X is located near the terminator, about one third of the way up from the southern pole of the Moon (at 2° East, 24° South). The prominent round crater Werner sits to its lower right. The X is predicted to become apparent after about 7 p.m. PST on Monday, Dec. 21, peak at about 11 p.m. PST, and then continue until about 1 a.m. This event should be visible anywhere on Earth where the moon is shining in a dark sky during that time window. The viewing window corresponds to 3:00 to 7:00 GMT on Dec. 22. Simply adjust for your difference from the Pacific Time zone. For observers in the easterly parts of North America, the moon will set while the X is visible.

Tuesday, December 22 — Ursid meteor shower peaks (pre-dawn)

(Image credit: Starry Night)

The annual Ursids meteor shower, produced by debris dropped by periodic comet 8P/Tuttle, runs from Dec. 17 to Dec. 23. The shower will peak during the early hours of Tuesday, Dec. 22, when seeing 5 to 10 meteors per hour is possible under dark skies. The best time to watch will be the hours before dawn. A waxing, half-illuminated moon will have set at around midnight, leaving the sky nice and dark for seeing meteors. True Ursids will appear to radiate from a position in the sky above the Little Dipper (Ursa Minor) near Polaris, but the meteors can appear anywhere in the sky.

Wednesday, December 23 — Gibbous moon meets Mars (evening)

(Image credit: Starry Night)

In the southern sky on Wednesday, Dec. 23, the waxing gibbous moon will sit a palm's width below (or 5 degrees to the celestial south of) reddish Mars. By the time the duo sets in the west after midnight, the diurnal motion of the sky will lift the moon to Mars' left. You can also try to spot Mars in binoculars during the late afternoon by using the moon below it as your guide.

Wednesday, December 23 — Moon occults star Nu Piscium (from 10:10 to 11:17 p.m. EST)

(Image credit: Starry Night)

On the evening of Wednesday, Dec. 23, observers in most of the continental USA and Canada can see the waxing gibbous moon pass in front of (or occult) the medium-bright star designated Nu Piscium (or ν Psc). The exact start and end times for the event vary by location. In New York City, the dark leading edge of the moon will cover the star at 10:10 p.m. EST, and the star will emerge from the opposite, lit edge of the moon at 11:17 p.m. EST. (Use Starry Night, or another astronomy app, to find out the timing where you live.) The event can easily be viewed in a backyard telescope — but your telescope will likely flip and/or invert the regular, binoculars view. Be sure to start watching a few minutes before ingress and egress.

Friday, December 25 — Sinus Iridum's Golden Handle (all night)

night sky december 2020 Sinus Iridum's Golden Handle

(Image credit: Starry Night)

On Friday night, Dec. 25, the pole-to-pole terminator that divides the lit and dark hemispheres of the waxing gibbous moon will fall to the left (or lunar west) of Sinus Iridum, the Bay of Rainbows. The circular, 155 mile (249 km) diameter feature is a large impact crater that was flooded by the same basalts that filled the much larger Mare Imbrium to its right (lunar east) — forming a rounded, handle-shape on the western edge of that mare. You can see it with sharp eyes — and easily in binoculars and backyard telescopes. The "Golden Handle" is produced when slanted sunlight brightly illuminates the eastern side of the prominent, curved Montes Jura mountain range that surrounds the bay on the top and left (north and west), and by a pair of protruding promontories named Heraclides and Laplace to the bottom and top, respectively. Sinus Iridum is almost craterless, but hosts a set of northeast-oriented dorsae or "wrinkle ridges" that are revealed under magnification at this phase.

Wednesday, December 30 — Full Oak Moon (at 03:28 GMT)

night sky december 2020 Full Oak Moon

(Image credit: Starry Night)

The December full moon, traditionally known as the Oak Moon, Cold Moon, and Long Nights Moon, always shines in or near the stars of Gemini. Since it's opposite the sun on this day of the lunar month, the moon is fully illuminated and rises at sunset and sets at sunrise. Full moons during the winter months reach as high in the sky as the summer noonday sun, and cast similar shadows. 

Thursday, December 31 — Algol at minimum brightness (at 7:10 p.m. EST)

night sky december 2020 Algol at minimum brightness

(Image credit: Starry Night)

Algol, also designated Beta Persei, is among the most accessible variable stars for skywatchers. Its naked-eye brightness dims noticeably for about 10 hours once every 2 days, 20 hours, and 49 minutes because a dim companion star orbiting nearly edge-on to Earth crosses in front of the much brighter main star, reducing the total light output we receive. On Thursday, Dec. 31 at 7:10 p.m. EST (or 0:10 GMT on January 1), Algol will reach its minimum brightness of magnitude 3.4, which is almost exactly the same as the star Rho Persei (or ρ Per) that sits two finger widths to Algol's right. When at its minimum, observers in the Eastern Time zone will find Algol high in the eastern sky. Five hours later, at 12:10 a.m. EST (or 5:10 GMT), Algol will be halfway up the western sky, and will have brightened to its usual magnitude of 2.1.

Planets

(Image credit: Starry Night)

Except for a few minutes before sunrise on the first two or three days of the month, Mercury will not be observable during December. After it passes superior conjunction with the sun on Dec. 20, Mercury will return to the southwestern evening sky — but its orbital position south of the shallow evening ecliptic will keep the planet too close to the horizon for observing until it swings farther from the sun in January.

(Image credit: Starry Night)

During December, Venus will continue to shine at a very bright magnitude -3.9 in the southeastern sky before sunrise — but it will be in the final stages of a lengthy pre-dawn apparition. Because the planet will be shifting sunward, it will rise 2.5 hours before the sun on Dec. 1, but only 90 minutes before sunrise at month-end. Meanwhile, the planet will traverse the stars of Libra until Dec. 17, dash through the northern section of Scorpius from Dec. 18 to Dec. 21, and then finish the month in southern Ophiuchus. Viewed in a telescope during December, our sister planet will exhibit a waxing, nearly fully-illuminated phase — and an average apparent disk diameter of 11 arc-seconds. On Dec. 11-12, the delicate sliver of the old crescent moon will pass Venus — occulting the bright planet at approximately 22:00 GMT for observers in easternmost Russia, Hawaii, and western North America. 

(Image credit: Starry Night)

During December, Mars will continue to be conveniently positioned for observing from dusk until several hours after midnight. It will reach its maximum elevation, more than halfway up the southern sky, in early evening, and then it will descend as it's carried west by Earth's rotation. Because Earth will be increasing its distance from Mars, the red planet will diminish in brilliance by half — fading from magnitude –1.1 on Dec. 1 to magnitude –0.24 on Dec. 31. Telescope views of the planet will show Mars' apparent disk diameter shrinking from 15 to 11 arc-seconds. At the same time, Mars will be traveling eastward across the V-shaped constellation of Pisces until early January. On Dec. 23, the waxing gibbous moon will pass 5 degrees to the south of Mars. 

night sky december 2020 jupiter saturn

(Image credit: Starry Night)

After a lengthy chase, Jupiter will finally catch and overtake more distant Saturn during December in a "Great Conjunction." As the month opens, the two planets will appear in the lower part of the southwestern sky for about two hours following sunset. Magnitude -2 Jupiter, which will shine 10 times brighter than magnitude 0.64 Saturn, will pop into view first as the sky darkens. Between Dec. 12 and Dec. 29, the two planets will be less than one degree apart — allowing them to be viewed together in the eyepiece of backyard telescopes. At their minimum separation on Dec. 21 — their closest since 1623 — the planets will sit only 0.1 degrees apart — a terrific opportunity to capture their markings, moons, and Saturn's rings in a single photograph taken through a telescope. Jupiter will span a 33 arc-second disk diameter — comparable to the apparent width of Saturn's rings. On that evening, they will sit quite low in the southwestern sky, and appear as a single point of light to your unaided eyes. At mid-month, Saturn will lead the pair out of the stars of Sagittarius and into Capricornus. On the nights surrounding Dec. 13, the two planets will pass only a degree north of the magnitude 9.9 globular star cluster Messier 75. By the end of December, the viewing window for the two planets will become quite short as they slide sunward into the western twilight. A pretty crescent moon will hop past them on Dec. 16-17.

(Image credit: Starry Night)

During December, blue-green Uranus will be visible all night long while it travels slowly westward in southwestern Aries — about 10 degrees south of Aries' brightest star Hamal, and 5 degrees north of the stars that form the top of Cetus' head. Try to view Uranus in mid-to-late evening, when it's more than halfway up the southern sky. The bright moon will pass a few degrees south of Uranus on Dec. 24, showing you where the planet is — but take advantage of the moonless first half of the month to try seeing the magnitude 5.7 planet with unaided eyes or binoculars.

(Image credit: Starry Night)

Neptune will be available for observing in the evening sky during December. The best time to view the distant planet will be as soon as the sky darkens fully — when the planet will be about halfway up the southern sky. From dark sky locations the magnitude 7.9 planet can be observed in good binoculars and backyard telescopes. Look in eastern Aquarius, about 0.8 degrees to the east of the medium-bright star Phi Aquarii, or φ Aqr. Both the planet and that star will appear together in the field of view of a telescope at low magnification (red circle).

Skywatching Terms

Gibbous: Used to describe a planet or moon that is more than 50% illuminated.

Asterism: A noteworthy or striking pattern of stars within a larger constellation.

Degrees (measuring the sky): The sky is 360 degrees all the way around, which means roughly 180 degrees from horizon to horizon. It's easy to measure distances between objects: Your fist on an outstretched arm covers about 10 degrees of sky, while a finger covers about one degree.

Visual Magnitude: This is the astronomer's scale for measuring the brightness of objects in the sky. The dimmest object visible in the night sky under perfectly dark conditions is about magnitude 6.5. Brighter stars are magnitude 2 or 1. The brightest objects get negative numbers. Venus can be as bright as magnitude minus 4.9. The full moon is minus 12.7 and the sun is minus 26.8.

Terminator: The boundary on the moon between sunlight and shadow.

Zenith: The point in the sky directly overhead.
 

Night Sky Observing Tips

Adjust to the dark: If you wish to observe faint objects, such as meteors or dim stars, give your eyes at least 15 minutes to adjust to the darkness.

Light Pollution: Even from a big city, one can see the moon, a handful of bright stars and sometimes the brightest planets. But to fully enjoy the heavens — especially a meteor shower, the constellations, or to see the amazing swath across the sky that represents our view toward the center of the Milky Way Galaxy — rural areas are best for night sky viewing. If you're stuck in a city or suburban area, a building can be used to block ambient light (or moonlight) to help reveal fainter objects. If you're in the suburbs, simply turning off outdoor lights can help.

Prepare for skywatching: If you plan to be out for more than a few minutes, and it's not a warm summer evening, dress warmer than you think necessary. An hour of observing a winter meteor shower can chill you to the bone. A blanket or lounge chair will prove much more comfortable than standing or sitting in a chair and craning your neck to see overhead.

Daytime skywatching: When Venus is visible (that is, not in front of or behind the sun) it can often be spotted during the day. But you'll need to know where to look. A sky map is helpful. When the sun has large sunspots, they can be seen without a telescope. However, it's unsafe to look at the sun without protective eyewear. See our video on how to safely observe the sun, or our safe sunwatching infographic.

Further Reading

All About Space Holiday 2019

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