RASNZ logo

Royal Astronomical Society of New Zealand

Eclipses of Saturn's Satellite Rhea in 2010


Eclipses of Rhea in 2010.

Events of Saturn's Satellites Rhea and Titan

Eclipses of the satellites of Saturn only occur for a year or two near the time when Saturn's rings are edge on to the Sun. This last occurred on 2009 August 10.

Saturn's satellites are a lot fainter than the four Galilean satellites of Jupiter, only eclipses of the two brightest, Titan (magnitude 8.6) and Rhea (magnitude 9.9) are likely to be observable through a small telescope. The inner satellites are fainter still and eclipses will occur close to Saturn's disk, making them difficult events.

Eclipses of Rhea started in July 2008 and occur at intervals of approximately 4.5 days. Those of Titan, which is considerably further from Saturn than Rhea, occurred in 2009, with the final eclipse of the series on 1 January 2010. The table shows the eclipses of Rhea which occur in 2010.

The dates and times of events are in Universal Time (UT). To convert from UT to NZST add 12 to the hours if they are less than 12. If the hours are 12 or more, subtract 12 from them and add 1 to the date. During NZDT add 13 to the hours if less than 11, else subtract 11 and add 1 to the date.




Table of eclipses of Rhea in 2010

Up to the opposition of Saturn on 22 March 2010 only disappearances of Rhea from eclipse are visible from the Earth. While Rhea is in eclipse and not visible it moves behind Saturn. Rhea emerges from eclipse while it is occulted behind Saturn and then emerges from occultation some time later. For these events the times of disappearance into eclipse and of reappearance from occultation are shown.

After opposition on Mar 22, the situation is reversed with only the reappearances of Rhea from eclipse being visible. The satellite moves into eclipse while it is occulted behind Saturn. For these the event the times shown are for the start of the occultation and for the emergence of Rhea from eclipse. In both cases the background for occultation events is in grey.

The distance of Rhea from the limb of Saturn at eclipse is small, just over 8" at a maximum, as at the beginning of January 2010. It is less nearer the date of opposition. The distance is considerably less than for Titan; 8" is not quite as far out as the edge of the rings. In addition Rhea is about 1.6 magnitudes fainter than Titan. Both these factors will make observation of Rhea's eclipses more difficult. A reasonable sized telescope will be needed to view them. Rhea will be to the north of and well clear of the rings, nearly on a level with Saturn's pole. The best eclipses for New Zealand are those during the morning hours in January.

Before opposition on March 22, eclipse disappearances of Rhea take place to the west of Saturn, after opposition eclipses reappearances take place to the east of Saturn. These will take place rather closer to the rings than the disappearances. If Saturn is allowed to drift through a telescopes field of view, it moves to the west.

Transits of the shadow of Rhea are difficult events due to the small size of Rhea's shadow on the face of Saturn. They occur close to mid way in time between pairs of eclipses.

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


Eclipses of Rhea
Date Time UT Date Time UT
Ecl. Disappearance Occ. Reappearance Ecl. Disappearance Occ. Reappearance
Dec 25 01:23 06:00 Dec 29 13:51 18:25
Jan 3 02:18 06:51 Jan 7 14:46 19:16
Jan 12 03:14 07:42 Jan 16 15:41 20:07
Jan 21 04:09 08:33 Jan 25 16:37 20:58
Jan 30 05:05 09:23 Feb 3 17:36 21:47
Feb 8 06:00 10:11 Feb 12 18:29 22:36
Feb 17 06:56 10:59 Feb 21 19:25 23:23
Feb 26 07:53 11:46 Mar 2/3 20:21 00:09
Mar 7 08:49 12:31 Mar 11/12 21:18 00:53
Mar 16 09:46 13:15 Mar 20/21 22:15 01:36
Mar 22 Saturn at opposition, eclipses move from west to east of the planet
Date Time UT Date Time UT
Disappearance Reappearance Disappearance Reappearance
  Mar 29/30 22:52 02:24
Apr 3 11:10 14:50 Apr 7/8 23:03 03:17
Apr 12 11:47 15:44 Apr 17 00:07 04:11
Apr 21 12:27 16:38 Apr 26 00:47 05:05
Apr 30 13:08 17:32 May 5 01:30 05:59
May 9 13:52 18:26 May 14 02:15 06:52
May 18 14:39 19:19 May 23 03:03 07:46
May 27 15:28 20:13 Jun 1 03:34 08:40
Jun 5 16:20 21:07 Jun 10 04:47 09:33
Jun 14 17:14 22:00 Jun 19 05:34 10:27
Jun 23 18:12 22:53 Jun 28 06:41 11:20
Jul 2 19:11 23:46 Jul 7 07:43 12:12
Jul 11/12 20:14 00:38 Jul 16 08:46 13:04
Jul 20/21 21:19 01:30 Jul 25 09:53 13:56
Jul 29/30 22:27 02:22 Aug 3 11:02 14:47
Aug 7/8 23:37 03:12 Aug 12 12:13 15:37
Aug 17 00:50 04:01 Aug 21 13:28 16:25
Aug 26 02:07 04:49  
  End of sequence of eclipses of Rhea

Top of page       RASNZ home page