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Events of the Galilean Satellites for December 2011


Table of Events visible from New Zealand for December 2011.

Events of Jupiter's Galilean Satellites

Eclipses, occultations, transits and shadow transit of all the three inner Galilean satellites will be occurring at regular intervals during December. A table of events visible during the month from NZ is included.

Eclipses occur when a satellite moves through the shadow of Jupiter. As it moves into the shadow the satellite will gradually fade from view and disappear. When it comes out of the shadow a faint spot of light will appear and gradually brighten.
Occultations occur when a satellite moves behind Jupiter as seen from the Earth. Hence during an occultation the satellite is hidden by the planet.
Transits occur when a satellite moves across the face of Jupiter as seen from the Earth.
Shadow transits occur when the shadow of the satellite cast by the Sun moves across the face of the planet

Occultations always start at the western limb of Jupiter and end at the east. Transits always start at the eastern limb of the planet and end at the west. In both cases the satellite will appear to "sink" into the bright limb of Jupiter at the ingress and gradually emerge from the limb of Jupiter at an egress.

In general eclipse events take place when the satellite is a small distance away from Jupiter as seen from the Earth, although they will occur very close to the planet near the time of opposition. After opposition as in December, eclipse events occur to the east of the planet.

All these events can be observed through a small telescope. Note that when Jupiter is viewed through an undriven telescope its image will drift to the west. This enables the west side of the planet to be determined.

In the case of disappearances into eclipse (EcD) the satellite is likely to be visible as it fades for a minute or two after the predicted time. For reappearances (EcR) the satellite will start to emerge a minute or two before the predicted time.

At present the north pole of Jupiter is tilted slightly towards the Sun. As a result of the slight tilt eclipses and occultations appear to take place to the north of the planet's equator, especially noticeable for the outer two satellites. Transits and shadow transits will cross the planet south of the equator. From New Zealand Jupiter's north pole is the lower pole of the planet.

Table of Galilean Satellite events visible from New Zealand for December 2011

The table shows the times, in UT, of events visible from New Zealand for December. To convert times to NZDT: for times less than 11 hours UT, add 1 to the hours and take the time as pm NZDT. Thus December 1 at 10:08 UT is 11.08 pm NZDT on December 1. For times after 11 hours UT, add 1 to the date and subtract 11 hours. Thus December 1, 14:16 UT is 3:16 am NZDT on December 2.

Times of events are adapted from those given by Dave Herald's OCCULT 4 program.

Explanation:
Satellites: 1 = Io, 2 = Europa, 3 = Ganymede, 4 = Callisto.
EcD = Eclipse disappearance, EcR = Eclipse reappearance
OcD = Occultation disappearance, OcR = Occultation reappearance
TrI = Transit Ingress (start), TrE = Transit Egress (end)
ShI = Shadow transit start, ShE = Shadow Transit end.

Date Time UT,  Event Time UT,  Event Time UT,  Event Time UT,  Event
December 1 10:08, 2 OcD 14:16, 2 EcR 14:56, 1 OcD  
December 2 12:06, 1 TrI 12:56, 1 ShI 14:16, 1 TrE 15:06, 1 ShE
December 3 09:11, 2 ShE 09:23, 1 OcD 12:24, 1 EcR  
December 4 08:42, 1 TrE 09:35, 1 ShE    
December 6 10:16, 3 TrI 12:08, 3 TrE 13:58, 3 ShI  
December 8 12:29, 2 OcD      
December 9 13:53, 1 TrI      
December 10 09:20, 2 ShI 09:50, 2 TrE 11:10, 1 OcD 11:46, 2 ShE
  Dec 10 cont. 14:19, 1 EcR      
December 11 09:20, 1 ShI 10:31, 1 TrE 11:31, 1 ShE  
December 12 08:48, 1 EcR      
December 13 13:46, 3 TrI      
December 17 09:45, 3 EcR 09:46, 2 TrI 11:56, 2 ShI 12:13, 2 TrE
  Dec 17 cont. 12:58, 1 OcD      
December 18 10:10, 1 TrI 11:16, 1 ShI 12:20, 1 TrE 13:26, 1 ShE
December 19 08:53, 2 EcR 10:43, 1 EcR    
December 24 09:03, 3 OcR 11:52, 3 EcD 12:12, 2 TrI  
December 25 12:00, 1 TrI 13:12, 1 ShI    
December 26 09:16, 1 OcD 11:32, 2 EcR 12:38, 1 EcR  
December 27 09:51, 1 ShE      
December 31 10:43, 3 OcD 12:50, 3 OcR    

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