Observing Window: June 2015 – Jupiter and Venus Conjunction


With warm summer nights upon us there are few things better than spending the early evening outside with cool drink in hand. While you’re out, take a look at the western sky about one hour after sunset. Except for the Moon in the southeast, the two brightest objects in the evening sky are Jupiter and Venus. They’ve been closing in on each other all month long on their way to a planetary conjunction on July 1st. A conjunction is a term used to describe two astronomical objects that cross the same line of right ascension, the astronomical equivalent of longitude here on Earth. Conjunctions can be very close, but aren’t always. That’s why close passes like the one occurring late this month are special and fun to watch. Over the next week you can watch them march closer and closer to one another until they are separated by a mere one-third of a degree, which is less than a Moon diameter. Their closest separation will be June 30th. The best time to observe is looking west around 9PM, although a keen eye can observe them earlier. Venus and Jupiter are just below the constellation Leo and its bright star Regulus. The constellation Gemini is setting, but its two bright stars Castor and Pollux are just visible low on the horizon to the northwest, although these will be faint under the light of the nearly full Moon, which will reach full on July 1st.


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