December Sky Notes
Written by John StapletonAn Update with Lucy
This time last year NASA’s Lucy space probe to the asteroids was busy gathering data and images of its first flyby target. This was a Main Belt asteroid, located between Mars and Jupiter and in the nearer region of the Asteroid Belt to Mars. The target did not even have an official name when the probe was launched in 2021, but in February 2023 the International Astronomical Union announced the official designation and name as 152830 “Dinkinesh”. This is an Ethiopian word in the Amharic language for the Lucy hominid fossil, discovered in Ethiopia in 1974, after which the space probe is named. The name means “You are Wonderful”
During this encounter Lucy discovered that Dinkinesh has a tiny companion, now named Selam (Amharic for “Peace” and the name of another fossil hominid) which orbits the asteroid so closely it almost looks like they might touch. Such a body is called a “contact binary”.
Lucy’s next target, which it will reach in April 2025, will be the Main Belt asteroid 52246 Donaldjohanson, named after the discoverer of the Lucy fossil. But, before this, in a counter-intuitive manoeuvre, Lucy will pass by the Earth on December 13th in a “slingshot” orbit to gain enough speed and momentum to reach the zone of the asteroids and be able to carry on towards the orbit of Jupiter where the probes main objects of study, asteroids captured by the giant planet’s gravitation, lay. Lucy will encounter the first of these captured asteroids, known as the Trojans, in 2027.
National Astronomy Week
The Torbay Astronomical Society anticipates a busy start to the New Year as the first week of February (1st through to 9th) is National Astronomy Week. This has been timed to coincide with the view of a string of planets visible in the night sky. Anyone interested in this event or booking some help from the society for an event of their own, please contact us on the following link.
Sky Notes
Please note all times given in this article are in GMT and as the clocks have changed that is the current time.
Sky Schedule
Sun: Throughout December the Sun sets before 4.30 and there are just 8 hours of daylight. The Winter Solstice (shortest day) occurs on December 21. On this date the Earth is closer to the Sun than at any other time in its orbit. We experience Winter in the Northern Hemisphere because the North Pole is tilted away from the Sun and its warming energy is spread over a greater area on the surface of the Earth.
Mercury: Mercury is visible in the morning sky, rising about an hour before the Sun. It reaches its greatest elongation (distance East) from the Sun on 25th. If you observe before the Sun rises above your horizon it will be safe to scan the sky with binoculars to try and locate this elusive little planet which is currently seen against the background stars of Ophiuchus.
Venus: Venus is easily the brightest object (other than the moon) in the evening sky throughout the month, It is seen against the background stars of Sagittarius biut will move into Aquarius before the end of the month.
Mars: The distinctly red planet, Mars is rises at about 7:00pm and is visible in Cancer, It doubles in brightness as the month progresses.
Jupiter: Jupiter is a brilliant object throughout the night and is well placed for observation. Jupiter is currently seen against the background stars of Taurus and can be seen in the south-eastern sky. The Galilean moons can be seen with a good pair of binoculars or a small (bird-spotting) telescope. DSLR images of the planet will also pick up the moons. The cold winter skies (if they are clear) give a much clearer and steadier image in a telescope or binoculars making observations much more satisfying. Jupiter will reach its closest point to the Earth on December 6th and opposition (opposite the Sun and due South in the sky on 7th.
Saturn: The ringed planet can be found against the stars of Aquarius in the Southern sky, setting around 11:oopm This is the last opportunity to view the ringed planet for a while. Its rings are now closed up (from our point of view) and this is why it is becoming fainter, although still a naked-eye object.
Uranus and Neptune: Uranus is visible all night long throughout December and is seen against the background stars of Aries on the border of Taurus, and close to the Pleiades star cluster. At magnitude 5.7 it is visible in binoculars. Look for a tiny greenish disc compared to the pinpoints which are the stars. Neptune is seen against the background stars of Pisces close to the border with Aquarius. At magnitude 7.8 it will require large binoculars or a larger telescope to find it and a larger telescope to discern its disc. Neptune displays a smaller and truly blue disc compared to that of Uranus although it will appear only as a bluish star to most small instruments. The planet sets around midnight.
Meteor Shower: December contains a number of minor meteor showers that occur throughout the month. These are not very active and have low meteor counts but can make it worthwhile “keeping an eye out” for shooting stars against the dark, winter skies, throughout the month. There are two major meteor showers due in December. The first, which peaks on the night of 13th, is the Geminids. The Geminid shower is the only shower associated with an asteroid rather than a comet. This asteroid is called Phaethon. The Geminid shower can be intense, and a New Moon the night before makes this ideal for observations this year. The second shower this month is the Ursids (maximum on 21st) that seem to emanate from a point in the constellation of Ursa Minor, which also contains the Pole Star.
Comet: There are no predicted bright comets this month. However, the minor planet (or Asteroid) 15 Eunomia will be visible at magnitude 8.2, and should be visible in binoculars. The minor planet can be found in the constellation of Auriga, and lie well above the horizon for most of the night. This passage will continue throughout the whole month, so you need to find the speck of light that changes position over the month.
Moon: The New Moon occurs on December 1st with First Quarter on 8th, Full Moon then follows on 15th December and Third Quarter on 22nd. The next cycle then begins with a New Moon on December 30th.