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Wednesday, 19 December 2018  •  Tuesday, 11 Birch Moon 2018/19 (night)

Watching the night sky in Birch Moon 2018/19

8 December 2017 - 5 January 2019

Map of night sky at full moon: 22 December, 17:49 UTC
Northern hemisphere perspective, aligned on the ecliptic. Morning sky to the left, evening to the right.

night sky map for Birch Moon 2018/19

At the start of the lunar month, Saturn is in the west as night falls. On 8 and 9 December, as seen from Europe and Africa, the new crescent moon is in the sky with Saturn, immediately after sunset. As seen from the Pacific, the moon passes very close to the north of Saturn between 05:00 and 06:00 UTC on 9 December, and from Yakutsk, the moon occults Saturn between 14:10 and 14:44 (05:10 and 05:44 UTC), just before sunset. From Khandyga, east of Yakutsk on the Aldan River, the moon occults Saturn from 14:17 to 14:48 (05:17 to 05:48 UTC), just after sunset. If you are looking at Saturn that evening with binoculars, swing just 1.5 degrees to the south to see the beautiful Sagittarius Cluster. After the first week of the month, Saturn disappears into the twilight, passing the far side of the sun on 2 January.

Mars is further out in the evening sky, setting in the late evening. It moves the constellation Aquarius into Pisces on 21 December. The moon is nearby on 14 December. By the end of the month, it is as faint as the now out-of-view Saturn.

Venus is the very bright morning star heralding the dawn. See if you can continue to see it as the sun rises, especially at the end of the lunar month, as it approaches its greatest elongation west of our common star, as seen from our skies.

On 15 December, Mercury reaches 21.3° west of the sun in the eastern morning sky, less easy to see from the southern hemisphere until nearly the end of the month, but a good view from the northern lands above the south eastern horizon.

Jupiter comes out from behind the sun and appears in the morning sky around the time of the waxing half moon, climbing up more slowly than Mercury. Particularly from the northern hemisphere, bright Jupiter will help you see the fainter Mercury above.

As Mercury sinks down into the sunrise again, it draws nearer to Jupiter, and passes less than a degree north of the brighter planet on 21 December. The nearest pass is seen from New Zealand, and the Pacific north of it. As seen from Europe, the two planets are close on the mornings of 21 and 22 December. Well above the Mercury-Jupiter pair is the very bright Venus.

On the mornings of 1-4 January, the old moon is in the morning sky with Venus, Jupiter and Mercury. As seen from Europe and Africa, the moon is either side of Venus on 1 and 2 January, close north of Jupiter on 3 Jan and above Mercury on 4 Jan, though by then Mercury is hard to see in the twilight.

At dark moon, there is a partial eclipse of the sun visible from Japan, Korea, NE China, Pacific-facing parts of eastern Siberia and the Aleutian Islands. The greatest eclipse is near Srednekolymsk in Yakutia, Russian Federation, at 12:42 local time on 6 Jan (01:42 UTC), with the noontime winter sun very low on the Arctic horizon. 61.9% of the sun is covered by the moon as seen from here. At Magadan in the nearby Magadan Oblast, 60% of the sun is covered at 12:37 (01:37 UTC). From Adak in the Aleutian Islands of Alaska, 44% is covered at 16:26 on 5 Jan (6 Jan, 02:26 UTC). In Japan, 42% of the sun is covered from Sapporo at 10:14 on 6 Jan (01:14 UTC), and 29% from Tokyo at 10:07 (01:07 UTC). At Beijing in China, the moon starts biting into the upper limb of the the sun as it’s rising at 07:36 on 6 Jan (5 Jan, 23:36 UTC) and 20% is covered at maximum eclipse at 08:35 (00:35 UTC). From Ulaanbaatar in Mongolia, the sun rises at 08:41 (00:41 UTC) during the eclipse, but the maximum eclipse is past.

It is possible that there will be a naked-eye comet this month: Comet 49P/Wirtanen, though at the time of writing, it is looking a little less likely than previously thought. It is due to be at the bottom of the map, just to the right of the main stars of Eridanus, at the start of the lunar month. Then it travels up through Taurus, passing between Aldebaran and the Pleiades around 16 Dec, to be where it is shown on the map at the time of full moon. Its brightness is a lot less certain than its trajectory, but sometime in the first half of December it may well become visible to the naked eye in a dark sky, and brighten up to its maximum late in December. Look out for it particularly at Christmas, as it passes close to the left of Capella, before heading through Lynx towards Ursa Major.

Look out for the brilliant Geminid meteors on the night 13/14 December, the Ursids (northern hemisphere) on the night 22/23 December, and the Quadrantids on 3/4 January. After midnight is the best time.

The month ahead: Rowan Moon 2019

6 January - 4 February 2019

Map of night sky at full moon: 21 January, 05:16 UTC
Northern hemisphere perspective, aligned on the ecliptic. Morning sky to the left, evening to the right.

night sky map for Rowan Moon 2019

At full moon on 21 January, there is a total eclipse of the moon, visible in Europe in the early hours, and also in the Americas. The penumbral phase begins at 02:36 (UTC); this is when the first area on the moon has the first small amount of light blocked by the Earth, and is hard to see; the partial phase starts at 03:33, and is when the first area of the moon has its direct sunlight completely blocked by the Earth, and you can normally see some darkening before this happens, as more and more sunlight is blocked from the leading edge of the moon. Totality lasts from 04:41 to 05:43, and this is when the whole of the moon has all of its direct light blocked; however, some red light still reaches the moon through the Earth’s atmosphere. If you were standing on the moon, you’d see a fiery red ring around the Earth. The partial phase ends at 06:50, and the penumbral phase at 07:48, just before moonset in SE parts of Britain.

Mars is in the evening sky, and sets in the late evening. The crescent moon is nearby on 12 January.

Mercury may still be just visible in the dawn at the start of the month, especially as seen from the southern hemisphere, before it moves towards the far side of the sun. Further up in the eastern sky is Jupiter, rising about two and a half hours before the sun, and shining brightly in the pre-dawn sky. Further still out from the dawn is Venus, which reaches 47°W of the sun on 6 January, and shines very brightly and prominently during the last part of the night. As the month progresses, Venus approaches the less bright Jupiter, and the two will look very well together in the east before it starts getting light. On the morning of 22 January, Venus passes north of Jupiter, and the moon is between Jupiter and Venus on the morning of 31 January.

By the end of the month, Saturn makes its way from behind the sun into the eastern morning sky, and you should be able to see the three planets in a curving line; in order out from the dawn, they are Saturn, then Venus, then Jupiter. On the morning of 2 February, the moon is very close to Saturn, and occults it in the dark as seen from parts of Western Europe and the Maghreb, but the moon is a very old crescent, and near to the sunrise, so there are few places where the occultation can be seen well. The only part of Britain & Ireland where the occultation can be seen at all is South-East England. From London, the occultation starts well before moonrise, and ends at 06:33 (UTC) when the moon and Saturn are still very near the SE horizon. When the occultation ends in Paris at 07:32 (06:32 UTC), the moon and Saturn are a little higher in the SE, although the twilight will be somewhat brighter. In Barcelona, the occultation also starts before moonrise, and finishes at 07:27 (06:27 UTC), before the start of civil twilight. Here you may well be able to see Saturn emerge from behind the dark edge of the moon. In both Rome and Tunis, the occultation starts when the moon and Saturn are high enough above the horizon to be seen fairly easily, but ends in daylight. Saturn begins to be covered by the lit edge of the moon in Tunis at 06:18 (05:18 UTC) and in Rome at 06:28 (05:28 UTC).

William Morris
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