Download Opposition of Saturn - Hong Kong Observatory

 Opposition of Saturn Opposition of Superior Planets A superior planet revolves around the Sun in an orbit further away from the Sun than the Earth. Mars, Jupiter, Saturn, Uranus Neptune, and Pluto are superior planets in
the Solar System. When a superior planet, the Earth and the Sun align in a straight line with the Earth in between, it is known as “opposition”. When the superior planet and the Earth lie on
the opposite sides of the Sun, it is known as “conjunction” (Figure 1). During opposition, the superior planet will be closest to the Earth and it would be a suitable time for observing the superior planet. Figure 1 Relative positions of a superior planet, the Earth and the Sun during opposition and conjunction of the superior planet. Opposition of Saturn Saturn is the second largest planet in the Solar System and the sixth planet away from the Sun. Saturn is characterized by the Saturn ring, which is composed of icy and rocky particles. Saturn revolves around the Sun with a period of about 29.5 years. Opposition of Saturn will occur about once every 378 days. The last Saturn opposition occurred on 18 December 2002 and the next occurrence will be on 1 January 2004. As Saturn has just passed the perihelion of its orbit in July 2003, it is still relatively close to the Sun. During the opposition on 1 January 2004, Saturn will be relatively bright, reaching a visual magnitude of about ­0.3 to ­0.5*. This will be a good time to observe Saturn and its ring structure. A telescope with 30 times or above magnification is preferred in observing Saturn. * Visual magnitude is a measure of the brightness of a celestial object. The visual magnitude of a faint star is large and positive. The brighter a star is, the smaller the visual magnitude will be. The brightest celestial objects will have negative magnitudes (visual magnitudes for the Sun and full moon are ­26.8 and ­12.5 respectively). In a clear night, the faintest stars that can be observed by naked eyes in the countryside would have a magnitude of around +6. Observation of Saturn in Hong Kong The position of Saturn in the night sky in Hong Kong in January­March 2004 is shown in Figure 2 below. Figure 2 Night sky in Hong Kong from January to March 2004. Details on the times of rise, transit and set of Saturn from 31 December 2003 to 1 January 2004 are shown below. Rise of Saturn
5:46 p.m., 31 December 2003 in the east­northeast
Transit of Saturn
0:27 a.m., 1 January 2004 elevation around 90 degrees
Time of opposition
5:56 a.m., 1 January 2004 in the west­northwest, elevation around 15 degrees
Set of Saturn
7:07 a.m., 1 January 2004 in the west­northwest
Other Sites on Opposition of Saturn : Hong Kong Space Museum U.S. National Aeronautics and Space Administration (NASA)