Overtaking the King

This is what the opposition of Jupiter means.

Planets’ space paths in March and April, with sightlines from Earth at April 7.  The view is from 15° north of the ecliptic plane.  The dashed line is the vernal equinox direction.  The planets are exaggerated 300 times in size; Jupiter, 50 times; the Sun, 5.

Earth overtakes Jupiter on the inside, so that Jupiter is directly outward from – opposite to – the Sun.  Around this time, Earth itself is being overtaken on the inside by Venus (the moment of this “inferior conjunction” was March 25) and Mercury (the moment will be April 20).

The more exact moment when Jupiter is at opposition is April 7, 21h Universal Time, which is 4 PM by Central U.S. summertime clocks.  So the nearest you can get to it is the evening that follows.

Far out beyond Jupiter shine the stars of Virgo.

 

4 thoughts on “Overtaking the King”

  1. Hi, Guy,

    My planetarium program shows Jupiter being closest to Earth about 24 hours AFTER opposition. Is that correct?

    1. That’s correct. Planets’ nearest approaches to Earth would coincide exactly with their oppositions only if their orbits were circular. Jupiter was at aphelion on Feb. 17, so it’s now in a part of its orbit that is curving slightly inward. You can figure out the result of that bit of geometry more quickly than I could describe it. The nearest-to-Earth moment comes almost exactly 24 hours after opposition, this time. It’s also shown in the side-by-side lists of Jupiter’s oppositions and nearest approaches in Jean Meeus’s “Astronomical Tables”, page 25. I mention these nearest approaches separately in my calendar only for Mars, which has the most eccentric orbit of the outer major planets, so that the difference can be a matter of days.

  2. Your 3-D description is enriching. As obvious as it is, I never thought of being as physically close to Jupiter as possible at the midnight hour closest to opposition. Your wording of the stars shining far beyond Jupiter further enhanced my sense of the 3-D view.

    I had a similar epiphany as a teenager. I was gazing at the moon when it dawned on me that I was looking at a sphere rather than a flat disc.

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