Meteor Showers

The Geminid meteor shower may be seen from the 4th – 20th December. It peaks on the 14th – 15th December, when the moon is a waning gibbous, so not great conditions. It is one of the most active showers of the year and some years the strongest, with peak rates of 100 meteors an hour. It’s the one major shower that shows good activity before midnight.

They are slower than most other meteors and often appear to last longer. The brightest often break up into numerous luminous fragments that follow similar paths across the sky.

The bright shooting stars are associated with asteroid (dwarf planet) 3200, Phaethon, the remains of a spent comet. Geminids tend to be most numerous around 2am when Gemini, their point of origin, is almost overhead. This shower produces a good proportion of bright events.

(Click image for larger view)

There is a second meteor shower in December, The Ursids, active 17-26th and peaks overnight on the 22nd- 23rd. This shower is fragments of Comet 8P/Tuttle, which produces about 5-10 meteors an hour, occasionally rising to 25 per hour. Maximum in 2022 occurs at New Moon, so conditions this year are extremely favourable. The radiant (point of origin) of the meteors is in Ursa Minor, The Little Bear, some 12° from the celestial North pole.

December Overview

Looking North, Ursa Major has now swung around and is starting to ‘climb’ in the east. The fainter parts in the southern part of the constellation are now in full view. The other bear Ursa Minor, hangs below Polaris in the north.

Directly above it is the faint constellation of Camelopardalis, with the other inconspicuous circumpolar constellation Lynx, to the east. Vega is just above the horizon in the north-west and Deneb and Cygnusremain visible farther west.

In the east, Regulus and the constellation of Leo are beginning to rise above the horizon. Cancer stands high in the east, with Gemini even higher in the sky. Perseus is at the zenith, with Auriga and Capella between it and Gemini. Because it is so high in the sky, now is a good time to examine the star clouds of the fainter portion of the Milky Way, between Cassiopeia in the west to Gemini and Orion in the east.

Looking South, the fine open cluster of the Pleiades is due south around 22:00, with the Hyades cluster, Aldebaran and the rest of Taurus clearly visible to the east. Auriga (with Capella) and Gemini (with Castorand Pollux) are both well-placed for observation. Orion has made a welcome return to the winter sky and with Canis Minor (with Procyon) now well above the horizon and Canis Major (with Sirius, the brightest star in the sky) rising before midnight. The small, poorly known constellation of Lepus lies to the south of Orion.

To the west, Aquarius has now mostly disappeared and Cetus is becoming lower, but Pisces is still easily seen, as are the constellations of Aries, Triangulum and Andromeda above it. The Great Square of Pegasusis starting to plunge down towards the western horizon and because of its orientation, it appears more like a large diamond than a square.

Winter solstice – 21 Dec 22 at 21:48 UTC. The South Pole of the earth will be tilted toward the Sun, which will have reached its southernmost position in the sky and will be directly over the Tropic of Capricorn at 23.44 degrees south latitude. This is the first day of winter (winter solstice) in the Northern Hemisphere and the first day of summer (summer solstice) in the Southern Hemisphere.

In the south, the meridian* provides the boundary between the faint, sprawling constellations of Cetus and Eridanus – now on the wane – and the glittering winter groups that are now in the ascendancy, providing a great contrast. Taurus straddles the meridian, whilst Orion and the remainder of his retinue lie just to the east. Capella, in Auriga, lies just 7° from a position at the zenith, the honour of which currently belongs to neighbouring Perseus.

Many depictions of the constellations show the bright star Alnath as belonging to both Auriga and Taurus but it is in fact a member of the latter, designated as b Tauri. The area in and around Auriga contains a number of open clusters, with the brightest being M37 at magnitude +5.6. M35 is slightly brighter (+5.1) and sits at the feet of the celestial twins (Gemini).

Looking west, the head of the flying horse (Pegasus) has already set. Despite this M31 is still at a good elevation, with the outstretched lines of stars that form Andromeda pointing to the zenith. Those lines, of course, lead us to Perseus whose sword handle is perfectly placed to display the Double Cluster.

The northern aspect sees Vega and Deneb moving towards the horizon. Ursa Minor points down towards the northern horizon and Draco, with the dragon head down on the meridian*. The larger Bear (Ursa Major) is now beginning to climb to the east of the pole, whilst Cassiopeia and Cepheus descend to the west. If you haven’t yet identified the faint stars of Camelopardalis then now would be a good time to do so, as it lies due north and close to the zenith.

meridian* (meaning)  In astronomy, the meridian is the great circle passing through the celestial poles, as well as the zenith and nadir of an observer’s location.

Decembers Object Challenge

Messier 1, The Crab Nebula

Messier 1 (M1), also known as the Crab Nebula, Taurus A, or NGC 1952, is an expanding supernova remnant and pulsar wind nebula. Messier 1 is located in the northern constellation Taurus, the Bull. It has an apparent magnitude of 8.4 and can be seen with binoculars in good viewing conditions.

To find M1 start at the Hyades the V shaped star cluster dominated by the bright red super giant star, Aldebaran in Taurus. Follow a line up from Albebaran  to the star Zeta (ζ) Tauri and the nebula is located 1 degree northwest of that star.

The Crab Nebula is the only supernova remnant listed in Messier’s catalogue and the most famous object of its kind in the night sky. The nebula has a total luminosity 75,000 times that of the Sun and lies at a distance of 6,500 light years from Earth.
The Crab Nebula is the result of a supernova explosion, SN 1054, that was observed by Chinese astronomers in 1054 AD. It was the first deep sky object to be associated with a historical supernova explosion.

Messier 1 is about 11 light years (3.4 parsecs) in diameter and keeps expanding at a rate of about 1,500 kilometres per second. The supernova remnant contains the Crab Pulsar, a rapidly rotating neutron star that spins at a rate of 30.2 times per second. The pulsar, also catalogued as PSR 0531+21, is the youngest one observed. It emits radiation in optical, radio, ultraviolet, X-ray and gamma ray wavelengths.

Comets
As I mentioned at the October meeting, comet C/2022 E3 (ZTF) is well worth looking for and keeping an eye on. C/2022 E3 (ZTF) is a long period comet that was discovered by the Zwicky Transient Facility on 2 March 2022. Upon discovery the comet had an apparent magnitude of 17.3 and was about 4.3 AU (640 million km) from the Sun. The object was initially identified as an asteroid, but subsequent observations revealed it had a very condensed coma, indicating it is a comet.

During October and November, it is situated in Corona Borealis and hopefully brightening steadily. It is a late evening object in October, switching to the early morning hours as we head into November. Perihelion (when it is closest to the Sun) is on 12 January 2023; it becomes circumpolar and possibly a good binocular object. The closest approach to Earth will be on February 2, 2023, at a distance of 0.29 AU (43 million km), by which time it is expected to become a naked-eye comet from a dark site, but as always, firm predictions of comets can always fall apart!

ISS

For more info go to https://www.heavens-above.com/PassSummary.aspx?satid=25544  and if you make a free account there and enter your location it gives you a precise timing and starmaps.

Have a very Merry Christmas and a Happy New Year with mince pies and clear skies!

Mick