The starry sky in December

Sky Guide December 2020

https://www.bresser.de/c/de/astro-news/sky-guide/dezember-2020/

The longest night of the year is approaching: On 21 December at exactly 11.02 am is the winter solstice. At this time the sun reaches its lowest noon elevation and climbs just 18.5 degrees above the horizon.

It is then only light for a little over 8 hours - the night to 22 December lasts almost 16 hours - of which 12 hours are pitch black and without any disturbing twilight. Stargazers will be pleased, because there is really enough time for the magnificent winter constellations. Saturn and Jupiter also have a surprise in store and in the middle of the month it seems that stars are raining down.

Full details of the December highlights as well as information on worthwhile deep sky observing objects this month can be found in our recently published Sky Guide for December 2020. We will give you an overview here in advance:

Showdown in the race: Jupiter overtakes Saturn

For months - you have certainly followed it - the gas giant Jupiter and the ringed planet Saturn have been competing with each other. Jupiter has moved ever closer to Saturn. Shortly before Christmas, a showdown will take place: at the beginning of winter, on 21 December, Jupiter will catch up with Saturn and pass the ringed planet to the south. The two gas giants are so close together that they appear as a bright double star. What you see there is called the Great Conjunction: Viewed from Earth, the two planets are aligned. Such an event only happens every 20 years. So don't miss it, because the next Great Conjunction will be in 2040. But the two giant planets will not be so close together then.

This is how you will find the rare spectacle: Jupiter and Saturn can only be seen on the southwest horizon in the early evening. On 21 December, between 17:00 and 18:00, both planets are about a hand's breadth above the south-west horizon. The brighter and larger of the two is Jupiter.

Jupiter and Saturn as the star of Bethlehem?

If the assumption that it could be the Star of Bethlehem from the Christmas story should force itself upon you, you are not so wrong. Johannes Kepler already interpreted the triple conjunction of Jupiter, Saturn and the Sun in the year 7 BC as the Star of Bethlehem. At that time, Jupiter and Saturn were facing the Sun together, which made both planets standing next to each other shine even brighter than we will experience on 21 December this year. Incidentally, the last triple conjunction took place at the turn of 1980/81. Venus and Mars remain with us - albeit less spectacularly

Earth and Mars are moving further and further apart over the course of the month, which is why Mars is clearly losing brightness (from -1.1 mag to -0.3 mag over the course of the month). Nevertheless, it remains a striking companion through the night. Venus also withdraws slowly from the morning sky and rises later and later: At the beginning of the month it still appears at about half past five in the morning, but on 31 December it does not appear until about seven o'clock. But Venus remains the brightest star in the sky after the sun and moon

Many wishes free: Shooting star showers in mid-December

In the middle of the month - between 6 and 16 December - the Geminides' shooting stars illuminate the long December nights. The meteors seem to come from the constellation Gemini and from there they flit in all directions. The highest rate of falling, with up to 120 meteors per night, is expected from 13 to 14 December. Every two to three minutes, assuming clear skies, you should then be able to spot a shooting star. Romantics should not forget to make a wish: According to the vernacular, these wishes will come true.

Sparkling winter pictures: Within reach

When it gets dark in the evening, the winter pictures have all already appeared in the eastern sky. It is highly visible and easy to recognise by its three prominent belt stars: Sky Hunter Orion. Its right foot star, the blue and white shimmering rigel, forms one of the six corners of the winter hexagon. The other five corners are formed by the yellowish kapella in the Carrier, the red aldebaran in the Bull, the bright and sparkling Sirius in the Great Dog, Prokyon in the Little Dog and Pollux in the Twins.

Did you know that both Sirius and Prokyon are within reach in cosmic dimensions of the earth? Sirius is just 8.7 light years away from us, Prokyon 11. giant star Rigel, on the other hand, is a whole 1500 light years away - but because of its size, this young star emits so much light that it still stands radiantly bright in the firmament.

There can hardly be a more glittering end of the year. We wish you a merry and reflective Christmas season. Stay healthy!