Astronomy Guide to the night sky, December 2023

Astronomy

ASTRONOMY GUIDE TO THE NIGHT SKY – DECEMBER 2023

With the Newbury Astronomical Society

The chart above shows the night sky at 21:00 on 15th December 2023

Click on the chart to enlarge and click to the side of the chart to close

The chart above shows the night sky looking south at about 20:00 GMT on 15th December.  West is to the right and east to the left.  The point in the sky directly overhead is known as the Zenith and is shown (in red) at the upper 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 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 Capricornus (the Goat), Aquarius (the Water Carrier), Pisces (the Fishes), Aries (the Ram), Taurus (the Bull), Gemini (the Twins), Cancer (the Crab) and Leo (the Lion).

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.  Jupiter and Saturn are still well placed in the southern and south western early evening sky this month.

The summer constellations are still prominent in the early evening sky in the west.  Only just visible is Hercules (the Hunter).  Following Hercules is 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 through the lower part of the Summer Triangle.

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 and down through Auriga and Orion to the south eastern horizon.

Prominent in the south is the constellation of Pegasus (the Winged Horse).  The main feature of Pegasus is the square formed by the four brightest stars.  This asterism (shape) is known as the Great Square of Pegasus.  The square is larger than might be expected but once found is easier to find again.  The Great Square can be used to judge the condition of the sky for observing.  If stars can be seen within the square there seeing should be good.  If no stars can be seen then seeing will not be good.

Moving into full view in the south east is the constellation of Taurus (the Bull).  The most obvious star in Taurus is the lovely Red Giant Star called Aldebaran.  It appears slightly orange to the ‘naked eye’ but it is very obviously orange when seen using binoculars or a telescope.  Aldebaran is located at the centre of the ‘flattened’ X shape formed by the brightest stars in Taurus.  At the end of the top right (upper west) arm of the ‘X’ is the beautiful ‘naked eye’ Open Star Cluster Messier 45 (M45) known as the Pleiades (or the Seven Sisters).  It really does look magnificent using binoculars.  See the following pages.

Following Taurus is the constellation of Gemini (the Twins).  The two brightest stars in Gemini are Castor and Pollux and they are named after mythological twins.

To the south of Taurus and Gemini is the spectacular constellation of Orion (the Hunter).  Orion is one of the best known constellations and hosts some of the most interesting objects for us amateur astronomers to seek out.  We will be having a closer look at Orion in the January issue of this magazine.

WHERE TO FIND THE PLANETS THIS MONTH

Mercury is the smallest planet and closest to the Sun.  It will be difficult to observe this month as it was in Superior Conjunction (in front of the Sun) on 20th October.  Mercury will be very difficult to see all through this month.

Venus is shinning very brightly in the early morning eastern sky.  It rises at 03:00, about four hours before sunrise.  Venus was at its Greatest Westerly Elongation 23rd October it is now moving closer to the Sun to pass behind the Sun in Superior Conjuction.

Mars is currently in conjunction with the Sun (passing behind the Sun) on 18th November so cannot be seen.

Jupiter is observable for most of the night from about an hour after it rises over the eastern horizon at about 13:30.  Jupiter will be at its best position for observing at about 20:30 when will be due south and a little higher in the sky.  The cloud markings and the four brightest (Galilean) moons will be visible, even using a smaller telescope, and with the turbulent air just above the horizon.  Jupiter is probably the best planet to observe because its cloud bands are quite easy to see and the four brightest moons especially the inner two can have their movement tracked even during one observing period (one hour).

Saturn is the first planet to rise over the eastern horizon around midday so it will be in daylight.  It can be seen as soon as it gets dark but is best at 16:30.  Saturn will look small in a small telescope and not much bigger in a medium sized telescope but the ring will be visible even using a small beginner’s telescope.  The best time to observe Saturn this month will be 17:00.

Uranus is just observable this month using a small telescope but a larger telescope will produce a better view.  It now rises in the east just as the sky darkens.  Uranus will be best seen later in the night as it rises higher in the sky.  It will be best at about 21:30 when it will be in the south.

Neptune rises at about 12:20 so can be in the sky as the Sun sets and will be at its best in the south at 18:00.  Neptune will need a telescope to see it looking like a small blue ‘fuzzy’ star.  It will be a little difficult to see, even when using a telescope in the late summer sky.

The Newbury Astronomical Society is currently commissioning a new website.

Link to Newbury Astronomical Society website: Home – Newbury Astronomical Society

Direct link to full What’s Up (observing guide) What’s Up November 2023: Whats_Up_December_2023.pdf – Google Drive

To read our monthly magazine click on: December Magazine

Our next meeting will be at Stockcross Village Hall on Wednesday 20th December 2023 starting at 19:00 until 21:00.

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