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Planetary Conjunctions

See the Planets page for more information about the planets in the Solar System.

The word planet comes from a Greek word meaning wanderer. Astronomers in ancient Greece and ancient China called them wandering stars because the planets look like stars that wander across the sky. Because they move at different speeds they sometimes catch up with and overtake each other and stars.

A conjunction occurs when two celestial bodies (stars, planets, Moon etc) appear in the sky very close to each other. A planetary conjunction occurs when two planets appear in the sky very close to each other.

A particular sort of conjunction called a greatest conjunction (Jupiter and Saturn opposite us from the Sun) is a possible contender for the Star of Bethlehem.

May 2011 – Conjunctions

Sometimes several planets are involved, such as in May 2011 when Mercury, Venus, Mars and Jupiter were all in the same small portion of the sky at once. Each pair of those planets had their own closest approach to each other. Mars and Jupiter kicked things off on 1 May 2011 with a conjunction (picture of 5 planets and Moon) where they were separated by only 24 minutes of arc – less than the diameter of the full moon. Another impressive conjunction occured on 11 May when Jupiter and Venus – both very bright – appeared 37 minutes apart. Sky and Telpscope have a QuickTime animation (and an article) showing the relative positions of the planets over the month, as seen fom the northern hemisphere.

Monday 16 May 2011 – Photo Update

The conjunctions haven't finished yet. Jupiter is on its own at the top, then the very bright Venus is in the middle with the much dimmer Mercury out to the right. Mars is much dimmer and straight below Venus.

Of course Earth is in the shot, and the obelisk on top of One Tree Hill is just visible over the trees.

Sunday 22 May 2011 – Photo Update

Very good viewing conditions meant another good opportunity to take photographs, not long before the closest approach of Venus and Mars.

Jupiter is on its own at the top, then the very bright Venus was the topmost of the trio with Mars quite dim down to the left and Mercury down to the right.

The moon was also visible, but well off to the left of these views.