Close Conjunctions Make Us Wonder: Do Planets Occult Planets?

The Mars-Jupiter conjunction (with the star Zubenelgenubi nearby) plays out over my neighbor’s house — lit by moonlight — about 6:30 this morning. Bob King

If there’s such a thing as a pleasant 18 below zero morning, today was it. Mars and Jupiter mesmerized. The two were so close they looked identical to a double star viewed in a telescope. How fun to just look up and split them with eyes alone.

(Top) Even through a 150mm telephoto lens, several of Jupiter’s moons were visible this morning.
(Below) Jupiter and Mars photographed with an iPhone at 76x in my scope. Bob King

My friend Greg, who lives in northern Wisconsin, also had clear skies. The sight made him wonder if planets ever got so close that they occulted (covered up) one another. Yes! This can happen but it’s exceedingly rare because the orbits of all the planets are slightly tilted with respect to each other. For a planet to occult another, each planet must arrive at the point where their orbits cross at the exact same time — as seen from Earth. That’s a tall order! If the planets appeared as big as the moon or sun, it would happen more frequently, but they’re so very far away and tiny, the alignment must be precise.

Here’s a list of “upcoming” events:

  • Venus occults Jupiter on Nov. 22, 2065. This will be visible shortly before sunrise and in broad daylight from the eastern half of the United States. Venus will pass directly in front of the southern edge of the planet.
  • Mercury occults Neptune on July 15, 2067. Occurs only at the North Pole but with nearly 24 hours of daylight, Neptune would be invisible. Sorry 🙁
  • Mars occults Jupiter on Dec. 2, 2223. Visible in Europe (in daylight) and other eastern hemisphere locales.
My children will see the 2065 occultation (better not be cloudy!), but we’ll have to leave the next one to our future descendants. Stellarium

There are no occultations of Saturn by Jupiter until sometime after the year 6000, but there will be a close conjunction on Dec. 21, 2020 visible during evening twilight from many locations. Minimum separation of 6 arc minutes (one-fifth a moon diameter) happens at noon Central time.

The very close conjunction of Jupiter and Saturn will be a spectacular sight at dusk sight on Dec. 21, 2020. This is the view from the Midwest after sunset through a small telescope. Stellarium

Lots of us will be around for the Saturn-Jupiter event but far fewer for that first occultation in 2065. The predictability of future events is one of the joys of the astronomy hobby. I just wish it didn’t remind us so matter-of-factly of our mortality.

5 Responses

  1. crocodilebomb

    Stay warm out there AB, also extra points for Zubenelgenubi. I remember someone saying the Zubens of Libra are among the few Babylonian words still in use? You would be the person to ask.

    1. astrobob

      Hey crocodile,

      The name Zubenelgenubi is actually Arabic and means “southern claw.” It’s possible however that the claw reference goes back even farther.

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