The Night Sky This Month: December 2019

Winter Solstice
The winter solstice at Stonehenge

The Sun starts December traveling eastwards through the constellation Ophiuchus, and will cross into the constellation Sagittarius on the 18th, four days before the Winter Solstice occurs on the 22nd in the Northern Hemisphere, and the Summer Solstice occurs in the Southern Hemisphere.

December also sees an annular solar eclipse on the 26th, but sadly this eclipse will not be visible in Western Europe. It will however, be visible from Saudi Arabia, southern India, northern Sri Lanka, and large swathes of the Indian Ocean. Meanwhile, a partial eclipse will be visible from Northern Australia and much, if not most of Asia.

The Moon Phases in December 2019

Note that Decembers’ Full Moon will be one of the highest Full Moons recorded during this year, which means that it’s very high elevation will greatly affect the visibility of meteors during the Geminid shower, which peaks on the 14th.

First Quarter Full Moon Last Quarter New Moon
December 4th December 12th December 19th December 26th

Depending on seeing conditions, some Earthshine may be visible during the waning crescent Moon between the 21st and the 25th, and again during the waxing crescent Moon between 25th and the last day of the year.

The Planets In December 2019

Mercury rises about 2 hours before the Sun for the first week or so of the month, but note that it will not rise more than about 2 or 3 degrees above the south-eastern horizon. By the middle of the month, the little planet will become lost in the Sun’s glare, and will therefore not be visible for the rest of December.

Venus is now moving eastwards through Sagittarius on its way to Capricornus and can be seen shining brightly low on the south-western horizon in the early evening. The planet will reach a point of opposition with Saturn on the 11th and will be only one degree to the southward of Pluto on the 15th. Venus will be the brighter of the two planets, shining at magnitude -4.0, while Pluto will be at magnitude +14, making it barely visible even with binoculars. On the evening of the 28th, the waxing crescent Moon will approach Venus in the constellation Capricornus, with both objects being about 10 degrees above the southwestern horizon. On the 29th, the Moon will be within 6 degrees to the eastward of Venus, so be sure to look for this pretty pairing if the weather and seeing conditions allow.

Mars rises about three hours before the Sun and will remain a predawn object throughout December. However, since the planet is now at a great remove from Earth, it will be rather dim at a magnitude of only +1.6, making it impossible to discern surface detail. Nonetheless, on the morning of the 28th, the Red Planet will be only four degrees away from the waning crescent Moon, both objects rising to about 12 degrees above the southeastern horizon. Depending on seeing conditions, it may be possible to see the first stars of the constellation Scorpius making their appearance below the Mars-Moon pairing.

Jupiter is now approaching a point of conjunction with the Sun, and will therefore not be visible during the entire month of December.

Saturn starts the month setting about 2 hours after the Sun, which reduces to only one hour by month’s end. Moreover, Saturn is both rather dim, shining at magnitude +0.6, and very low on the horizon, so binoculars might very well be needed to spot it in the south-west. If seeing conditions allow, it might be possible to spot Saturn within 3 degrees of the thin waxing crescent Moon on the 27th, when both objects will be within 5 degrees of the southwestern horizon.

Uranus crosses the meridian at about 8 PM (GMT) and although it is at the threshold of naked-eye visibility at magnitude +5.72, it might be possible to spot the planet with binoculars in the constellation Aries, and close to the Aries-Cetus-Pisces border. Look for the planet about 8 degrees to the southward of the star Sheritan (beta Arietes).

Neptune will culminate about mid-month when it will shine at magnitude +7.9. The planet is now in the constellation Aquarius, so look for it just under one degree to the westward of the 4th magnitude star Phi Aquarii.

Meteor Showers in December 2019

December 2019 sees two meteor showers, one of them being one of the biggest meteor showers of the year, namely:

The Geminid meteor shower is expected to peak on the 14th, although increased meteor activity runs from about the 4th to the 17th. Unlike other showers that originate from active cometary debris, the Geminids originate from the dust of asteroid 3200 Phaeton, which is a “dead” cometary nucleus. Although this shower is known for its relatively bright meteors, the Full Moon will extinguish all but the very brightest meteors this year. Nonetheless, the Geminids will radiate from a point in the constellation Gemini that should be almost overhead for observers from mid-northern latitudes during the peak hours.

– The Ursid meteor shower is expected to peak on the night of the 22nd/23rd, but only about 5-10 meteors per hour are expected to appear this year. However, since there will be very little moonlight during the peak, it should be possible to view most, if not all meteors. Look for the point of origin about 12 degrees from the celestial North Pole in the constellation Ursa Minor.

Deep Sky Objects to Look For In December 2019

Constellations that are prominent at this time of year include Lepus, Orion, Taurus, and Auriga, with the first stars of Scorpius just appearing above the southern horizon. Sadly, though, while Taurus and Orion contain many conspicuous deep-sky objects that are easy to spot with binoculars and/or small telescopes, Auriga and Lepus are not only dim and difficult to spot; they are with a few exceptions, also largely devoid of easy targets for modest amateur equipment. Below are some brief details of two such exceptions:

Messier 79 (M79, NGC 1904)

Messier 79
Image Credit: NASA, ESA Hubble Space Telescope

Located about 41,000 light-years away in the constellation Lepus, this magnitude 8.56 globular cluster is thought to have originated outside of the Milky Way. Like M54, another extra-galactic globular cluster, M79 likely originated in the Canis Major Dwarf Galaxy, a satellite of the Milky Way. The dwarf galaxy is currently engaged in a tug-of-war with the Milky Way, which it will almost certainly not survive intact.

Messier 38 (M38, NGC 1912)

Messier 38
Image Credit: 2MASS/UMass/IPAC-Caltech/NASA/NSF

Located only about 4,200 light-years away in the constellation Auriga, this open cluster has about 100 members that are spread out over a distance of roughly 13 light-years. The more remarkable aspect of this cluster is the fact that the brightest stars in the cluster faintly resemble the Greek letter “Pi”, which is sadly only apparent in medium to large telescopes. Nonetheless, the brightest star in the cluster is a magnitude 7.9 yellow giant that is at least 900 times more luminous than the Sun. If this were put into perspective, an observer looking back at the Sun from the cluster would see the Sun as an exceedingly faint magnitude +15.3 star.

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