The massive planet’s most northerly opposition, in its twelve-year cycle through the twelve constellations of the zodiac, comes in January and in Gemini. This recurring pattern, which has a solemn elegance, is explained in the Jupiter pages of Astronomical Calendar 2026.
Here is the scene tomorrow evening as Jupiter climbs into view over the horizon opposite to the setting Sun. In company with the Twins – or half-twins.
According to the tangled story of Leda and the swan, and her offspring Castor, Pollux, Helen, Clytaemnestra – a story embedded in the legend of Troy – Castor was the son of her husband the king of Sparta, but Pollux was fathered by the god.
Which may be why Pollux is the brighter of the two stars (their magnitudes are 1.16 and 1.58) and why Jupiter visits his lovechild more closely – 6.5° from Pollux on December 14. Jupiter is in apprparent retrograde motion along the ecliptic as we pass nearest to it.
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The day *after* Jupiter’s most recent opposition I read this on the Sky and Telescope website:
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Paolo Molaro at the Osservatorio Astronomico di Trieste, Italy, writes us,
At 08:40 UT, there will be a perfect alignment of the Sun, Earth, and Jupiter. For an observer located in the Jovian system, the Earth will transit across the [tiny] solar disk, with a total duration of approximately three hours.
Although Earth and Jupiter reach opposition every ~12 years (the Jovian orbital period), perfect Sun–Earth–Jupiter alignments of this kind are exceptionally rare. They occur in a series of five events spaced by 12 years, followed by a long hiatus. The 2026 transit will be the final event of the current series; the next such series will not begin until 2109.
This alignment offers a particularly favorable opportunity to observe the Galilean moons of Jupiter. Owing to the opposition surge, the satellites are expected to undergo a noticeable increase in brightness—possibly approaching one magnitude (though this estimate is approximate). Under optimal conditions, this enhancement could make the moons significantly easier to observe and, potentially, even visible to the naked eye. Observations using a coronagraph to suppress Jupiter’s glare should be especially rewarding.
The transit occurs on 10 January 2026, peaking at 08:40 UT, and will be observable from North America, making it particularly relevant for your readership.
https://skyandtelescope.org/astronomy-news/observing-news/this-weeks-sky-at-a-glance-january-9-18/
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Seen through binoculars and a small refractor, the Galilean moons were noticeably brighter than usual for a few days around opposition.
Interesting