December nights are the longest due to the fact that the winter solstice occurs in this month. As a result, they offer more opportunities for astronomical observations. The last month of the year rarely spoils us with clear skies, but it is rich in interesting astronomical events.
The visibility of the brightest planet, Venus, is gradually improving. By now, its radiance has probably caught your eye: The Evening Star is easy to see in the southwest as soon as the Sun disappears behind the horizon. Golden Saturn continues to move slowly through the constellation of Aquarius, and twice in December its largest Moon, Titan, will cast a shadow over the planet.
At the end of the first week of December, Jupiter, which is currently in the constellation Taurus, will be in opposition, so you can admire it all night long. In the middle of the month, a powerful meteor shower, the Geminids, will reach its peak. And on 25 December, the fastest planet, Mercury, will be in its greatest western elongation. Around this date, you will be able to observe all the planets of the Solar System throughout the night.
And we are also expecting a very rare phenomenon, although it is impossible to observe it directly – a second new moon within one calendar month. This new moon is traditionally called the Black Moon.
The undisputed king of the December sky is Orion, rich in bright stars. It is here that the only nebula that can be seen with the naked eye, the Orion Nebula, resides. A little to the south and east of this constellation, you can find the brightest star in the sky – Sirius α of the Canis Major. It never rises high in our latitudes, and thanks to the turbulence of the atmosphere, it shimmers with all colours in a spectacular way.
The list of events
👀 🔭 📷 1 December – new moon.
👀 🔭 📷 5 December – Moon (15%) conjunct Venus (-4.2m); at 02:07 a.m. the Moon will be 2.3° south of Venus, but by then both bodies will be below the horizon, so the best time to observe them will be the evenings of December 4 and 5, right after sunset.
👀 🔭 📷 6 December – transit of Titan’s shadow across Saturn’s disk.
👀 🔭 📷 7 December – Jupiter is in opposition.
👀 🔭 📷 December 8 – Moon (47%) conjunct Saturn (+1m); the exact time of the conjunction is 10:20 a.m. Kyiv time, long before the sunrise, but in the evening of the same day they will still be quite close to each other.
👀 🔭 📷 13 December – from 6:00 p.m. to 8:30 p.m., the Moon (96%) will pass by the scattered cluster of the Pleiades in the constellation Taurus, covering some of its stars.
👀 🔭 📷 13-14 December – the maximum of the most powerful Geminid meteor shower.
👀 🔭 📷 15 December – lunar full moon. The exact time is 11:02 a.m., when the Moon will still be below the horizon for Ukraine.
👀 🔭 📷 18 December – Moon (90%) in conjunction with Mars (-0.9m). Residents of most European countries and northern Canada will be lucky enough to observe the coverage, while in Ukraine, the bodies will be below the horizon at this time. During the night of 17-18 December, we will be able to observe the Moon’s gradual approach to the Red Planet.
👀 🔭 📷 21 December – at 11:20 a.m., the winter solstice will take place, which will start the astronomical winter.
👀 🔭 📷 22 December – transit of Titan’s shadow across Saturn’s disk.
👀 🔭 📷 22 December – maximum of the Ursids meteor shower with the radiant in the constellation Ursa Minor; the forecast ZHR is 10.
👀 🔭 📷 December 25 – Mercury (-0.4m) is at its greatest western elongation at 22° from the Sun, a good chance to see the planet shortly after sunset.
👀 🔭 📷 31 December – the second new moon of the calendar month (it will occur at 12:27 a.m.), which is also called the Black Moon.
A detailed overview of the most interesting events
1 December: a new moon gives us a chance to enjoy faint deep space objects
The New Moon phase will occur on 1 December at 06:21 a.m. UTC (1:21 a.m. UTC -5), so the nights closest to this date will be optimal for observing nebulae, galaxies, and star clusters. This month we recommend paying attention, first of all, to the Orion Nebula, the only nebula visible to the naked eye. It is located directly under the Orion Belt, in the so-called Sword region, and its magnitude is +4m. To see the central stars of the nebula, you’ll need a telescope. More experienced observers are advised to pay attention to the reflective nebula M78 in the same constellation. And for astrophotography enthusiasts, December will be the best month for wide-angle photography of Orion. For owners of small and medium-sized telescopes, Rigel will be an interesting star – it is an optically double star: a much dimmer star is visible next to the main white-blue supergiant.
The observing programme can be expanded to include a number of scattered star clusters: M38, M36, and M37 in the Auriga, and M35 in the Geminids not far from them.
6 and 22 December: Transit of Titan’s shadow across Saturn’s disc
A series of rare events continues, during which Saturn’s largest moon, Titan, casts its shadow over the planet. Such series include several transits within a few months, and approximately 15 years pass between the series. Currently, Saturn is moving away from Earth, making it difficult to observe such small details as the moon’s shadow on it.
On 6 December, Titan’s shadow will begin to creep over the planet at 6:32 p.m. UTC (1:32 p.m. UTC -5), and will slowly move as long as Saturn is above the horizon. The best time to observe is between 7:00 p.m. UTC (2:00 p.m. UTC -5) and 7:30 p.m. UTC (2:32 p.m. UTC -5) when the shadow will have fully entered the disc and (for Kyiv) the planet will be at an altitude of 18°-15° above the southwestern horizon.
On 22 December, the transit will begin at 5:30 p.m. UTC (12:30 p.m. UTC -5), and, once again, Titan’s shadow will be on the planet’s disc until it sets. The best time to observe is from 5:55 p.m. (12:32 p.m. UTC -5) (Saturn at 19°) to 6:30 p.m. (13:32 p.m. UTC -5) (15° above the horizon).
More details about these events can be found in the article dedicated to them.
7 December: Jupiter opposition
The largest planet in the Solar System is in opposition almost every year – approximately 13 months pass between Jupiter’s oppositions. An opposition of an outer planet is a configuration in which the Earth is exactly between the Sun and the planet, so that it reaches its peak brightness and is visible throughout the night. Even a small telescope or binoculars will allow you to see the planet’s disc and 4 of its largest moons: Io, Europa, Ganymede and Callisto.
An interesting fact: Jupiter will be in opposition on 7 December between 22 and 23 hours, but the planet will be at its closest distance of 611 million kilometres on 6 December at around noon. This is due to the slight elongation of the orbits of both the Earth and Jupiter.
Source: Tom Williams.
13-14 December: the Geminid meteor shower will be hampered by the full moon
The Geminids are a fairly wide stream that is active from 4 to 20 December. Although not as popular as the August Perseids, the Geminids are the most powerful meteor shower of the year. These meteors receive less attention, on average, due to the unfavourable weather conditions – cold and overcast – that are typical for December in our latitudes. The radiant of the stream is located in the constellation Gemini, which is where the name comes from. But you shouldn’t concentrate on this particular point, as meteor risks will appear all over the sky. The Geminid’s ZHR reaches a maximum of 150 – the number of meteors an observer could see in a perfect sky in an hour if the radiant were at its zenith. The meteors of this stream are quite slow: since the particles do not fly towards us, but catch up with the Earth, they enter the atmosphere at a speed of only 35 km/s, and therefore the ‘shooting stars’ have a yellowish rather than white colour. This year, unfortunately, the maximum activity of the stream occurs when the Moon is almost full, and it will disappear behind the horizon only in the early morning. Nevertheless, the Geminids sometimes contain quite bright meteors, and even meteors that can be seen even during a lunar full moon, especially if you try to hide in the shade.
22 December: Ursids – a meteor shower of medium power
Ursids will be active from 17 to 26 December, reaching a maximum on the 22nd. Although the expected ZHR is only 10, observations will be less disturbed by the Moon, which will be at 53% phase and will appear above the horizon only after midnight. In addition, these meteors can be a surprise. For example, in 1945, according to various sources, 100 to 170 meteors per hour were observed.
The radiant of the stream is located in the constellation of the Ursa Minor, near its second brightest star, Beta Ursae Minoris, so it is always above the horizon. The maximum of the stream is quite narrow, and is forecast to be around midnight from 22 to 23 December.
25 December: the largest western elongation of Mercury
The last chance to see Mercury this year is in the second decade of December. On the 25th, the fastest planet in the Solar System will move 22° westward from its central star, so it will be visible in the morning before sunrise almost exactly in the southeast. Therefore, for successful observations, you should choose a place so that this direction is open. Although Mercury is very bright, with a magnitude of -0.4m, it quickly melts into the bright colours of the morning sky. The optimal window for observing is very narrow – between 07:00 a.m. and 07:15 a.m. (for Kyiv), when the planet is 6°-8° above the horizon and the Sun is 8°-6° below it. The thin crescent of the old Moon can be a pleasant addition to the pre-dawn landscape.
To catch Mercury, you don’t have to see it on 25 December. The time period from 19 to 27 will be approximately equally favourable.
