The above figure shows the planets during the May 5, 2000 conjunction as viewed looking down on the solar system. Other kinds of planetary conjunctions happen at complicated intervals when more than two planets are involved.
Planet Earth,planet,sun Earth planet,sun,zodiac Mercury 117 days x 25 8 years Venus 585 days x 5 8 years Mars 780 days x 7 15 years Asteroids 468 days x 7 9 years Jupiter 398 days x 11 12 years Saturn 378 days x 29 30 years Uranus 369 days x 83 84 years Neptune 367 days x 163 164 years
The second column gives approximately the synodic period of the planet as seen from the Earth. This means that, as seen from the Earth, the location of the planet in our sky relative to the Sun's direction will repeat itself after the indicated number of days. But, each time, the background stars along the Zodiac will be different. In the third column, the multiplier tells you after how many synodic cycles, the planet will be seen against the same constellation. Example, for Jupiter, its synodic period is 398 days, Then 398 x 11 = 4378 days or 11.99 years. This means that if you see Jupiter tonight in the constellation Scorpio ( a guess), then in 12 years you will again see Jupiter in Scorpio. For Venus, if you saw it at Greatest Eastern Elongation 5 months ago in the constellation Virgo then in 585 x 5/365 = 8 years you will again see it at Greatest Eastern Elongation towards Virgo.
The next most complicated conjunction involves two other planets as viewed from the Earth. To figure out when two of these planets will have their next conjunction, you have to use this formula:
1 1 1
------ = -------- - ---------
Time S1 S2
so that for the very pretty Jupiter-Saturn conjunctions you have to wait
1 1 1
------ = ------- - ------- = 0.00013
Time 378 398
or Time = 7692 days or 21 years.
For more complex groupings you need a digital planetarium!
"When was the last time the five planets plus Sun and Moon were as close as the May 5, 2000 conjunction"
The answer is 1962 -- when there was a solar eclipse at the same time!
Minimum separation of 5 planets + Moon:
Event Date Separation
last February 5, 1962 15.8°
present May 17, 2000 19.5°
next September 8, 2040 8.3°
Minimum separation of 5 planets + Moon + Sun:
Event Date Separation
last February 5, 1962 15.8°
present May 5, 2000 25.9°
next March 20, 2675 22.6°
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