Astronomy Essentials

Jupiter: Closest to sun January 20, 2023

Jupiter with four moons and three shadows visible.
View at EarthSky Community Photos. | Sona Shahani Shukla in New Delhi, India, captured this photo of Jupiter during a triple transit on August 15, 2021. Sona wrote: “Super happy to have seen the rare event of triple shadow transit on Jupiter, though missed Callisto’s shadow transit (yeah the houses obstruct my views?). Io sprung a surprise entry into the frame and for a very brief moment casted it’s shadow!” Thank you, Sona!

Jupiter at perihelion in 2023

Jupiter’s September 26 opposition, when Earth in its orbit flies between Jupiter and the sun, places Jupiter opposite the sun in our sky. But Jupiter’s perihelion – its closest point to the sun – comes several months later on January 20, 2023 at 12 UTC. The distance between the sun and Jupiter that day will be 460 million miles (740 million km).

Simple diagram of orbits of Earth and a superior planet.
Opposition happens when Earth flies between an outer planet, like Jupiter, and the sun. Illustration via Heavens-Above.

A closer look at our orbits

Both Earth and Jupiter have orbits that are very nearly circular. They go around the sun on almost the same plane. But – in both cases – not quite.

Consider that, because Jupiter’s orbit is elliptical, not circular, Jupiter’s distance from the sun varies.

Likewise, Earth’s orbit is elliptical, not circular. Our distance from the sun varies, too.

Animated diagram, small black dot orbiting large blue object in elongated oval path.
This animation shows an orbit that’s vastly more elliptical than either Earth’s or Jupiter’s. Still, you get the idea. Perihelion = closest to sun. Aphelion = farthest from sun. Image via Brandir/ Wikipedia.

Jupiter’s orbit takes 11.9 Earth-years. Earth’s orbit takes one year.

Earth’s perihelion – or closest point to the sun – occurs every year around January 4th. For Jupiter, reaching perihelion isn’t so consistent.

The giant planet was farthest from the sun in 2017

Jupiter passed aphelion – its farthest point from the sun in its orbit – on February 18, 2017. Jupiter will reach perihelion – its closest point – on January 20, 2023.

So since 2017, Jupiter moves closer to the sun – bit by bit, closer and closer – every earthly day. And Earth’s change of distance (relative to the sun) is small compared to Jupiter’s. So while Jupiter was closest to Earth in September 2022, it will be closest to the sun in January 2023.

And that’s why Jupiter isn’t closest to the sun when our planet passes between Jupiter and the sun.

Geocentric ephemeris for Jupiter: 2022

Geocentric ephemeris for Jupiter: 2023

Geocentric ephemeris for sun: 2022

Geocentric ephemeris for sun: 2023

Bottom line: You’d think Jupiter would be closest to the sun on the day Earth passes between Jupiter and the sun. But, Jupiter’s 2022 opposition occurred months before its closest point to the sun.

January 20, 2023
Astronomy Essentials

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