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Events of the Galilean Satellites for April 2010


Table of Events visible from New Zealand for April 2010.

Events of Jupiter's Galilean Satellites

Eclipses, occultations, transits and shadow transit of all four Galilean satellites will be occurring at regular intervals during April. 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. Before opposition, as in April 2010, they occur to the west 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 very slightly towards the Sun. As a result of the slight tilt all events appear to take place almost in line with Jupiter's 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 April 2010

The table shows the times (in UT) of events visible from New Zealand for April.
The two events on April 2 take place before NZDT ends. By NZDT they occur on April 3 at 6:09 and 6:25 am respectively.
The remaining events take place after the start of NZST. To convert from UT to NZST for times greater than 12 hours UT (as in April) add 1 to the date and subtract 12 hours from the time Thus April 11 at 16:57UT is April 12 at 4:57 am NZST.
Jupiter was at opposition at the end of February, as a result there is only a limited number of events for April, most in the second part of the month.

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
April 2 17:09, 1 TrI 17:25, 3 EcD    
April 11 16:57, 2 ShE 18:25, 2 TrE    
April 13 18:01, 3 TrE      
April 17 17:33, 4 TrI 17:38, 1 EcD    
April 18 16:43, 2 ShI 17:07, 1 ShE 17:56, 1 TrE 18:24, 2 TrI
April 25 16:46, 1 ShI 17:40, 1 TrI    
April 26 17:16, 1 OcR      
April 27 18:29, 2 OcR      

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