The 'opposition' of Jupiter

Dear Tom,
I see a bright star in the sky in the eastern sky around 9 p.m. and then in the western sky around 4 or 5 a.m. What is it?

–Phyllis Roche

Dear Phyllis,
Astronomer Dan Joyce of the Cernan Earth and Space Center at Triton College in River Grove tells us, “This is very definitely Jupiter, which makes its closest approach to Earth for the next 12 years later this month.”
Jupiter, the largest planet in the solar system, will be at “opposition” on Sept. 21. In astronomical circles, a planet is said to be in opposition when it is directly on the opposite side of the Earth from the sun.
This is generally the closest that the planet comes to Earth and the time when it is most easily visible in the nighttime sky. At opposition (when the sun, Earth and Jupiter lie in a straight line), about 400 million miles will separate Earth and Jupiter.

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