Astroblog

The northern horizon at 3:13 am ACDST as seen from Adelaide on Sunday December 14 when the Geminid radiant is at its highest. The Geminid radiant is marked with a starburst. Similar views will be seen elsewhere in Australia at  a similar latitude and the equivalent local time. (click to embiggen).	The northern horizon at 1:46am AEST as seen from Brisbane on on Sunday December 14 when the Geminid radiant is at its highest. The Geminid radiant is marked with a starburst. Similar views will be seen elsewhere in Australia at  a similar latitude and the equivalent local time. (click to embiggen).	The northern horizon at 3:17 am AEDST as seen from Melbourne on Sunday December 14 when the Geminid radiant is at its highest. The Geminid radiant is marked with a starburst. Similar views will be seen elsewhere in Australia at  a similar latitude and the equivalent local time. (click to embiggen).

This year is a modest year for the Geminid meteor shower. The Geminids are an unusual meteor shower in that their parent body is 3200 Phaethon, an asteroid, rather than a comet. It is speculated though that Phaeton is actually a "gassed out" comet, and so the debris that makes up the Geminids may still be cometary particles, but is more likely broken rock fragments from its close approach to the sun.

The Geminids are usually a fairly reliable meteor shower but this year there will be some  interference from the Moon.

The Geminids have a broad peak and normally show good activity well before and after the peak on the day before and after. The nominal peak is December 14, 08h UT, that means in Australia this year most of the activity is concentrated on the morning of the 14th after sunrise, but there will still be decent rates before twilight, and on the 15th as well.

As the radiant doesn't rise until just before midnight (daylight saving time) in most of Australia and the radiant is highest (with the best meteor rates) in the early hours in a narrow band around 3 am local time, so you are going to lose some sleep for this.  Fortunately this is a Sunday, so you can sleep in after. 

Unfortunately, both Chrome and Firefox have changed their security settings to prevent plugins from running, and the flux estimator only runs under Internet Explorer now OR Edge in Internet Explorer mode (click on the triple dots once the page has loaded ), you have to have the JAVA plug-in loaded.

You can follow the progress of the shower at the IMO Geminids Live page. 

At 3.00 am in the morning AEDST (midnight, AEST) Castor (alpha Geminorum) is about four hand-spans above the horizon and almost due north. Pollux, the other twin, is less than a hand-span to the right again and below Castor. The radiant is just below Pollux. The best rates are when the radiant is highest, when it is due north, the Moon is low to the horizon and before astronomical twilight. This is around 3:30 am ACDST Adelaide ~3:00 ACST Darwin, ~1-1:30 am local time Perth and Brisbane and ~ 2:30-3:00 am AEDST Melbourne, Sydney and Hobart.

City	Time Radiant Highest	Moon Rise	Astronomical Twilight
Adelaide ACDST	3:13	2:09	4:09
Brisbane AEST	1:46	1:43	3:14
Darwin ACST	2:43	2:51	4:57
Hobart AEDST	2:38	1:24	2:39
Melbourne AEDST	3:17	2:08	4:00
Perth AWST	2:13	2:11	3:25
Sydney AEDST	2:52	1:46	3:56

When you get up, allow at least 5 minutes for your eyes to adjust and become dark adapted (even if you have stumbled out of bed in the dark, here's some hints on dark adaption of your eyes so you can see meteors better). 

Labels: geminids, Meteors, unaided eye

The Full Moon is Friday December 5. This is a perigee ("super") Full Moon. Saturn is high in the north-western sky. Jupiter is visible in the morning sky near the bright star Pollux. Jupiter is rising before midnight and is close to the waning moon on the 7th. Jupiter is still best in the morning.

The Full Moon is Friday December 5. This is a perigee ("super") Full Moon. The Moon is at Perigee, when it is closest to the Earth, on the 4th.

Labels: weekly sky

To be read in conjunction with listening to the second half of the Astrophiz November Sky Guide.
https://soundcloud.com/astrophiz/novemberskyguide224 Eastern sky on Sunday, December 7  as seen from Adelaide at 23:52 ACDST.  Jupiter is rising and is close to the waning Moon. 

December
5 December 2025	Perigee Full Moon ("super" Moon)
7 December 2025	Jupiter near waning Moon (4° apart) in morning sky, forming a line with the bright star Pollux.
14/15 December 2025	Geminid Meteor shower in the morning, some Moon interference
19 December 2023	Mercury, the thin Crescent Moon and the bright star Antares from a triangle low in the morning twilight, might need binoculars
22 December 2025	Earth is at Solstice
27 December 2025	Nearly First Quarter Moon near near Saturn (4° apart)  in the early evening sky

Moon:

December 4	Moon at perigee
December 5	Full Moon (perigee full Moon)
December 12	Last Quarter Moon (ideal for star gazing)
December 17	Moon at apogee
December 20	New Moon (also ideal for star gazing)
December 28	First Quarter Moon

 

Meteor Shower:
Geminids December the 14th contends with a last Quarter moon.

Locations on the same latitude as...	December 12	December 13	December 14 (peak)	December 15
Darwin	7 meteors/hr	14 meteors/hr	36 meteors/hr	29 meteors/hr
Brisbane/Perth	5 meteors/hr	9 meteors/hr	23 meteors/hr	23 meteors/hr
Sydney/Adelaide/Canberra	4 meteors/hr	7 meteors/hr	18 meteors/hr	16 meteors/hr

Sky looking south on Saturday December 20 s seen from Adelaide at 22:15 ACDST (90 minutes after sunset). 

 

 

 

 

 

 

Similar views will be seen from the rest of Australia at roughly the equivalent local time (90 minutes after sunset). 

Stars:

 In the Southern sky the dwarf galaxies, the Magellanic clouds, are rising. The Large Magellanic cloud will be in an excellent viewing position in the late evening.  The Large Magellanic cloud and the Tarantula nebula are magnificent objects.

If you look due South after astronomical twilight (and hour and a half after sunset) in a dark sky location you will see what looks like two wispy clouds but unlike clouds they don’t move, these are the Magellanic clouds, the dwarf companion galaxies to ours. The largest of the wisps, to the left of due south is the large Magellanic cloud. The Large Magellanic cloud lies at an approximate distance of 163,000 light years from us. The LMC has a prominent bar in its central region, which indicates that it may have previously been a barred spiral galaxy.

A line through Sirius and Canopus carried on will piece the heart of the LMC. Within the hazy disk of the LMC is a fuzzy star, this is the tarantula nebula. While it is not much to the unaided eye, and a mere fuzzy patch in binoculars, in a telescope it is outstanding. It is the most active star-forming region in the 30-odd galaxies including the Milky Way that make up the Local Group In a telescope you can see the spidery appearance for which it is named, a dozen or so incredibly hot massive stars at the centre of long tendrils of hot gas (why not octopus?).

There are also multiple open clusters and nebula and a globular cluster to explore with binoculars, so you can spend quite a bit of time on the LMC alone. In a telescope they are even better. Just south of the Tarantula nebula is a complex of clusters that repays exploration.

As well, the skies feature Orion the Hunter striding across the sky, The distinctive V shape of the Taurus the bull, and the beautiful Pleiades cluster. For us in the southern hemisphere the Pleaides are almost due moth at astronomical twilight. Try counting how many stars you see. Another name for the Pleiades is the seven sisters, can you see seven stars? 

The Southern Pleiades, a group of stars clustered around the star theta carina, is now readily visible two hand-spans above the southern cross. 

The Christmas holiday season will be a fantastic time to explore our skies.

Labels: Monthly sky, unaideed eye