Astroblog: Thursday December 23 to Thursday December 30

Tuesday, December 21, 2021

Thursday December 23 to Thursday December 30

The Last Quarter Moon is Monday, December 27. Four bright planets are seen forming a line in the early evening twilight. These are Mercury, Venus, Saturn and Jupiter. Venus is rapidly lowering in the sky heading towards Mercury. Mercury and Venus are parallel to the horizon on the 27th and closest on the 29th. Comet C/2021 A1 Leonard may be visible to the unaided eye and is clearly visible in binoculars. Mars is occulted by the Moon on the morning of 1 January 2022.

The Last Quarter Moon is Monday, December 27.

Morning sky on December 30 looking east as seen from Adelaide at 4:58 ACDST (60 minutes before sunrise). Mars is low in the twilight below the bright red star Antares with the Moon not far away. On January 1 the Moon occults Mars as seen from south east Australia. The inset shows the Moon and Mars at 4:53 ACDST as the Moon is just about to pass in front of Mars. Details for other sites are below.

Similar views will be seen throughout Australia at the equivalent local time (60 minutes before sunrise, click to embiggen).

Evening twilight sky on December 27 looking west as seen from Adelaide at 21:01 ACDST (30 minutes after sunset). Venus and Mercury are parallel to the horizon and Venus forms a line with Saturn and Jupiter.

The insets shows the telescopic views of Venus, and Mercury at this time. Venus is a very thin crescent now. Similar views will be seen throughout Australia at the equivalent local time (30 minutes after sunset, click to embiggen).

Whole sky showing the Jupiter, Saturn and comet C/2021 A1 Leonard, December 25, 22:18 ACDST, 90 minutes after sunset (click to embiggen). Orion, Taurus and the Pleiades can be seen above the eastern horizon.

Elsewhere in Australia will see a similar planetary line up that the equivalent time (90 minutes after sunset).

Comet C/2021 A1 Leonard as seen looking west
from Adelaide at 21:37 ACDST (60 minutes after sunset) on 25 December (Christmas day). Similar views will be seen in elsewhere in Australia 60 minutes after sunset.

Comet C/2021 A1 (Leonard) is this years “Christmas comet”. While not as spectacular as the “searchlight comet” Comet C/2011 W3 Lovejoy, it isa nice little binocular object. It is currently in outburst and has even been reported to be (just) visible to the unaided eye.

As it climbs higher we will get better views but it will fade rapidly, however, it should be easily visible in binoculars on Christmas day (unless it spectacularly disintegrates). More details and printable black and white charts here .

Mercury climbs higher in the evening twilight.

Venus is visible in the early evening twilight. I have been able to see Venus from just after sunset and it is easily seen over 2 hours after sunset, longer if you have a clear western horizon. Venus forms a line with Saturn and Jupiter. It is now a distinct crescent in even small telescopes. Venus is now heading rapidly towards the horizon.

Mars is rising higher in the twilight in the twilight. On Jan 1 2022 Mars is occulted by the thin crescent Moon. The occultation of Mars is seen in south eastern and south central Australia in the early morning on New Years Day. It will be visible from Adelaide, Hobart, Melbourne and Canberra. Sydney sees a graze 12 minutes before sunrise. The occultation will be low to the horizon with the thin crescent Moon covering Mars. In Adelaide this is after astronomical twilight and in the east with the best views, for Hobart, Melbourne and Canberra this is around nautical twilight.

Place	Disappears bright Limb	Reappears dark Limb
Adelaide ACDST	04:53	05:37
Canberra AEDST	05:31	05:47
Hobart AEST	05:30	06:11
Melbourne AEST	05:26	06:00
Sydney AEST	5:36	-

Jupiter is readily visible in the western sky when the sky is fully dark. Venus, Saturn and Jupiter form a line in the twilight sky which is joined by Mercury later in the week. Jupiter is still excellent in even small telescopes, but the window of telescopic observation is closing as it sets earlier.

Saturn is still excellent in even small telescopes, but the window of telescopic observation is closing rapidly as it sets earlier.

Printable PDF maps of the Eastern sky at 10 pm AEST, Western sky at 10 pm AEST. For further details and more information on what's up in the sky, see Southern Skywatch.

Star Map via Virtual sky. Use your mouse to scroll around and press 8 when your pointer is in the map to set to the current time.

Cloud cover predictions can be found at SkippySky.

Here is the near-real time satellite view of the clouds (day and night) http://satview.bom.gov.au/

Labels: weekly sky