Astronomy Essentials

Helioconjunction of Jupiter and Neptune on June 6

Helioconjunction: Circles indicating planet orbits and lines extending from the sun to 2 planets.
What is a helioconjunction? It’s a heliocentric, or sun-centered, conjunction. This space view, from 15 degrees north of the ecliptic plane, tries to clarify what will happen on June 6, 2022. The paths of Earth, Jupiter and Neptune are drawn for April, May and June 2022. The orange line is from the sun to Jupiter and Neptune at the time of the conjunction. The other lines are sight-lines from Earth to the 2 planets at the times of their geocentric conjunction (pink) and heliocentric conjunction (yellow). Earth is exaggerated 300 times in size, Jupiter and Neptune 50, the sun 4. Image via Guy Ottewell. Used with permission.

Originally published on June 2, 2022, at Guy Ottewell’s blog. Reprinted with permission. Jupiter will overtake Neptune on Monday, June 6, in the race of the planets around the sun. This event takes place once every 12.7 years.

Helioconjunction: Jupiter passes Neptune

Jupiter goes around the sun in just under 12 years. This is its sidereal period, the period in relation to the stars, or space in general. But when it comes around to where it last overtook Neptune, the more distant planet has moved slowly on. So Jupiter overtakes Neptune about 8.5 months later. The last heliocentric conjunction of these two planets was September 19, 2009. The next one will be tomorrow, Monday, June 6, 2022. The following one will be February 18, 2035.

The conjunctions as seen from Earth are called geocentric conjunctions. They are more irregular. As seen from Earth, the Jupiter-Neptune conjunction has already happened – in April 2022 – when we were out west of the sun and had a premature view of the planets’ lineup.

During that April 2022 event, Earth’s relatively rapid orbit made the planets appear to go into retrograde motion or move from side to side in the sky.

Triple conjunctions

If conjunctions of Jupiter and Neptune happen near the times of the planets’ oppositions – Earth passing both of them on the inside track – then we have a triple conjunction. So Jupiter appears to overtake Neptune, then falls back past it, then passes it again.

The last triple conjunction of Jupiter and Neptune was in 2009. The conjunction dates were May 2, July 10 and December 21.

Circles for planet orbits around the sun with lines from orbits to Jupiter and Neptune.
On this chart for 2009, the paths of the planets are drawn for the months from May to December. The orange lines are the conjunctions of the 2 types, heliocentric and geocentric, in the middle of this compound performance. In 2009, Jupiter was retrograding between June 15 and October 15, Neptune between May 28 and November 4, and their oppositions were on August 14 and 17. Image via Guy Ottewell. Used with permission.

Bottom line: On June 6, 2022 – as seen from the sun – Jupiter will overtake Neptune in the race of the planets around the sun. This is a heliocentric (sun-centered) conjunction, or helioconjunction.

June 5, 2022
Astronomy Essentials

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