Starship Asterisk*

Jupiter and Saturn Great Conjunction: The Movie

Explanation: Yes, but have you seen a movie of Jupiter and Saturn's Great Conjunction? The featured time-lapse video was composed from a series of images taken from Thailand and shows the two giant planets as they angularly passed about a tenth of a degree from each other. The first Great Conjunction sequence shows a relative close up over five days with moons and cloud bands easily visible, followed by a second video sequence, zoomed out, over 9 days. Even though Jupiter and Saturn appeared to pass unusually close together on the sky on December 21, 2020, in actuality they were still nearly a billion kilometers apart. The two gas giants are destined for similar meet ups every 19.86 years. However, they had not come this close, angularly, for the past 397 years, and will not again for another 60 years. If you're willing to wait until the year 7541, though, you can see Jupiter pass directly in front of Saturn.

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Can you please tell me why Jupiter and Saturn are moving in opposite directions in our sky? Thank you. I just recently found the page and I really love it! Thanks!

ZootMurph14 wrote: ↑Wed Dec 30, 2020 12:57 pm Can you please tell me why Jupiter and Saturn are moving in opposite directions in our sky? Thank you. I just recently found the page and I really love it! Thanks!

Just my guess, but I think that it has to do with the fact that Saturn (probably) shows "retrograde motion", i.e., appears to move backwards compared with Jupiter from our point of view, during some part of their orbits around the Sun.

I recommend the video at right, which shows the retrograde motion of Mars as seen from the Earth.

This video is longer, but it does an even better job of explaining retrograde motion.

Ann

Ann wrote: ↑Wed Dec 30, 2020 1:58 pm

ZootMurph14 wrote: ↑Wed Dec 30, 2020 12:57 pm Can you please tell me why Jupiter and Saturn are moving in opposite directions in our sky? Thank you. I just recently found the page and I really love it! Thanks!

Just my guess, but I think that it has to do with the fact that Saturn (probably) shows "retrograde motion", i.e., appears to move backwards compared with Jupiter from our point of view, during some part of their orbits around the Sun.

Both Jupiter and Saturn are currently in direct (prograde) motion, meaning both are moving in the same direction (eastward) against the stars. But we're not seeing their motion against the sky in this video, we're simply seeing their motion with respect to each other. Viewed this way, they will always appear to be moving in opposite directions, either toward each other or away, right?

When I watched the movie; Reminded me of Yo=yo's

I wonder if this happened 2,020 years ago with Venus thrown in the mix? pass the ice cold one.

Chris Peterson wrote: ↑Wed Dec 30, 2020 2:54 pm

Ann wrote: ↑Wed Dec 30, 2020 1:58 pm

ZootMurph14 wrote: ↑Wed Dec 30, 2020 12:57 pm Can you please tell me why Jupiter and Saturn are moving in opposite directions in our sky? Thank you. I just recently found the page and I really love it! Thanks!

Just my guess, but I think that it has to do with the fact that Saturn (probably) shows "retrograde motion", i.e., appears to move backwards compared with Jupiter from our point of view, during some part of their orbits around the Sun.

Both Jupiter and Saturn are currently in direct (prograde) motion, meaning both are moving in the same direction (eastward) against the stars. But we're not seeing their motion against the sky in this video, we're simply seeing their motion with respect to each other. Viewed this way, they will always appear to be moving in opposite directions, either toward each other or away, right?

Just thought I'd add a Stellarium simulation as a visual.
 
70-Hour Stellaruim Simulation - 12/20 00:00 → 12/22 22:00

A movie on a different timescale. This is just 3.8 hours, not long after the two planets made their closest pass. Even over this short period the relative motion between the two is obvious.
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