Mars will pass less than a degree north of Jupiter on August 14.
Conjunctions of Planets 4 and 5 (in order of their distance outward from the Sun) happen at intervals of about 2.24 years. The reason is that Mars, after passing Jupiter, goes around the Sun in 1.89 years (its sidereal period) and then takes some more time to overtake Jupiter, which, in its slower orbit, has moved on by about 74°. The intervals between the heliocentric conjunctions (as seen from the Sun) are regular, but the moving viewpoint of Earth makes them less so.
Our page about the Mars cycle displays the patterns of Mars’s roughly alternating years.
Here is how the present situation looks from out in space.
The viewpoint is 15° north of the ecliptic plane. Shown are the paths of the planets in August, and sightlines from Earth on Aug. 14. The Sun is exaggerated 4 times in size, the four inner planets 300 times, the giant outer planets (mostly out of the picture) 50 times. The dashed line is toward the vernal equinox direction, the zero point for mapping positions in the sky.
Mars and Jupiter are 66° out on the west (“right”) or morning side of the Sun. So they do not come into view until after midnight.
The angular separation between the planets will be 0.31°. Their distances from us are 1.44 and 5.38 AU (astronomical units, Sun-Earth distances); their magnitudes 0.8 and -2.2; their apparent widths about 6 and 36 seconds. These numbers mean that Jupiter is nearly 8 times farther away, yet appears about 6 times as wide and 16 times as bright.
It is always amazing to see, in an eyepiece, the cherry in front of the pumpkin and realize that the pumpkin is so much farther away.
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Very beauteous, especially since flanked by Aldebaran and Nath
After a few overcast nights, before dawn this morning there were lots of breaks in the clouds. Mars and Jupiter were in good view, dramatically close to one another, and Mars looked very red in contrast with brighter Jupiter. I hope to get another look when they’re even closer together tomorrow morning.
Saturn was visible too, and I found Uranus and Neptune with binoculars.