ASTRONOMY GUIDE TO THE NIGHT SKY
With the Newbury Astronomical SocietyThe chart above shows the night sky at 17:00 on 21st December 2020
The tour of the night sky this month starts early because the beautiful planets Jupiter and Saturn are moving ever closer towards the western horizon. They will be setting over the horizon at 19:10 at the beginning of December and setting at 17:45 by the end of the month. Fortunately the sky is getting dark earlier so there is still time to see the two Gas Giants appearing very close together in their planetary conjunction. They will be at their closest on 21st December when the pair will be visible together in the field of view of telescopes using a low power eyepiece but they will be setting at 18:15 on that evening.
West is to the right and east to the left. The point in the sky directly overhead is known as the Zenith or Nadir and is shown at the centre of the chart. The curved brown line across the sky at the bottom is the Ecliptic or Zodiac. This is the imaginary line along which the Sun, Moon and the planets appear to move across the sky. The brightest stars often appear to form a group or recognisable pattern; we call these ‘Constellations’.
Constellations through which the ecliptic passes this month are Sagittarius (the Archer), Capricornus (the Goat), Aquarius (the Water Carrier), Pisces (the Fishes), Aries (the Ram), Taurus (the Bull), Gemini (the Twins) and Cancer (the Crab, just off the chart to the east).
Just disappearing over the south western horizon is the constellation of Sagittarius (the Archer). It is really a southern constellation but we can see the upper part creep along the horizon during the summer. The central bulge of our galaxy is located in Sagittarius so the richest star fields can be found in the constellation along with many of the beautiful and interesting deep sky objects that we seek out (labelled in yellow print). The stunning binocular cluster M45 the Pleiades (Seven Sisters) are looking beautiful in Taurus towards the east of the Ecliptic.
The summer constellations are still prominent in the early night sky. The Summer Triangle with its three corners marked by the bright stars: Deneb in the constellation of Cygnus, Vega in Lyra, and Altair in Aquila. The Summer Triangle is very prominent and can be used as the starting point to find our way around the night sky. The Milky Way (our Galaxy) flows through the Summer Triangle passing through Cygnus, down to the horizon in Sagittarius. The Milky Way flows north from the Summer Triangle through the rather indistinct constellation of Lacerta (the Lizard), past the pentagon shape of Cepheus and on through the ‘W’ shape of Cassiopeia (a Queen), Perseus and Auriga (The Charioteer).
All the Superior Planets (those orbiting the Sun outside Earth’s orbit) are visible in the south. Jupiter and Saturn are most prominent in the south west in the early evening. Jupiter is very bright with Saturn very close by and getting closer still until they are very close together on 21st December (their closest CONJUNCTION). The Gas Giant Planets are followed across the sky by Neptune the most distant planet then the distinctly orange and bright Mars and completing the parade of planets is Uranus. The outermost planets Uranus and Neptune do really need a good large pair of binoculars to find and a telescope to see as small blue discs.
Mars was at its closest to Earth on 13th October when it was at Opposition (in the south at midnight GMT) and at its brightest this year. It is now moving away from us and will start looking smaller.
Planets observable: Jupiter, Saturn (very early evening), Neptune, Mars, Uranus (in the evening), Venus and Mercury (in the early morning in the east before sunrise).
There will be a Meteor shower called the Geminid Meteor Shower with a peak of activity in the early hours of the 14th December.
Follow this link to see the full ‘Monthly What’s Up’ guide to the night sky:
To see a full version of this article and a guide to the night sky with charts, read the Newbury Astronomical Society (NAS) – Monthly Magazines for Beginners on the Beginners website at: www.naasbeginners.co.uk.
All meetings of the Newbury Astronomical Society have been cancelled due to the Coronavirus. However virtual meetings will continue on-line using Zoom. Check the website above.