Farewell Parting Of The Evening Planets

Watch the interplanetary traffic in the southwestern sky during evening twilight in the coming week. This animation shows the planets’ changing positions from Dec. 5 through Dec. 12. Stellarium

Since late last month, Venus has been playing tag with the evening planets at dusk, providing lots of pretty viewing and photographic opportunities. I hate to break the news, but that’s about to end. Venus is now nudging toward Saturn and will pass it in conjunction on Dec. 10-11. Jupiter’s hunkered down in bright twilight and will soon depart the evening sky followed by Saturn several weeks later. Come Christmas Day Venus will stand alone in the western sky, the sole bright planet easily visible at dusk.

As Venus cycles around the sun very 225 days, it passes between the Earth and sun in inferior conjunction and on the opposite side of the sun in superior conjunction. During this time, we see it swing from one side of the sun to the other. Venus is currently between superior conjunction (top) and greatest elongation east (left). As it moves toward greatest elongation the bright planet appears to move upward and away from the sun in the evening sky exactly as it’s doing right now. Bob King

Such is the way of the solar system where nothing stands still. Watch the animation, which spans from Dec. 5-12, and you’ll see two things happening. Venus moves up and away from the sun, and Jupiter and Saturn move toward it. As we discussed in an earlier blog, what’s really happening is that Venus’s apparent distance from the sun is increasing from our perspective here on Earth. At the same time, Earth’s orbital motion around the sun makes the stars and planets slowly drift westward over time every about 1° a day equal to 4 minutes of time.

After Jupiter and Saturn pass in front of the sun in conjunction, they’ll move to its other side and return to the morning sky. There, they’ll join Mars for some wonderful conjunctions in the new year ahead. Stay tuned!

2 Responses

  1. Edward M Boll

    I saw Jupiter on the 4th, possibly for the last time. Yesterday was cloudy, and tonight I couldn’t see it. So, counting Earth, it was a 5 planet day.

Comments are closed.