{"id":4129,"date":"2022-10-16T08:58:59","date_gmt":"2022-10-16T12:58:59","guid":{"rendered":"https:\/\/www.fas37.org\/wp\/?p=4129"},"modified":"2025-05-03T09:32:24","modified_gmt":"2025-05-03T13:32:24","slug":"planetary-opposition-and-conjunction","status":"publish","type":"post","link":"https:\/\/www.fas37.org\/wp\/planetary-opposition-and-conjunction\/","title":{"rendered":"Planetary Opposition and Conjunction"},"content":{"rendered":"\n

FAS Astronomers Blog, Volume 30, Number 13.<\/strong><\/p>\n\n\n\n

You might have seen some articles recently (September 2022) about Jupiter\u2019s bright opposition. You also might remember Mars\u2019 opposition of 2018, which was the closest since 2003. But, what you ask, is an opposition? Let\u2019s find out.<\/p>\n\n\n\n

The eight (or maybe nine?) planets of our solar system orbit the Sun in a counterclockwise direction when viewed from the north. They all have very predictable orbits ranging from Mercury, the fastest at 88 days, out to Neptune at 165 years. A planet\u2019s orbit is referred to as its sidereal period<\/strong>, which is the time required to complete one orbit about the Sun.<\/p>\n\n\n\n

However, the perceived motion of the planets when viewed from the Earth is a bit more complicated because both the planets and the Earth are simultaneously moving about the Sun. The position of the planets relative the Earth and in our night sky depends on both motions.<\/p>\n\n\n\n

Elongation<\/strong> is a term that describes the observed angle between a planet and the Sun when viewed from the Earth. It can range from 0o<\/sup> when the planet is in the same direction as the Sun to 180o<\/sup> when the planet is opposite the Sun.<\/p>\n\n\n\n

Planets also have a synodic period<\/strong>, which is the time required to complete one full cycle in the night sky and return to the same position relative to the Earth. It is technically the time between any two successive oppositions or similar conjunctions (as defined below).<\/p>\n\n\n\n

Superior Planets<\/strong><\/u><\/p>\n\n\n\n

The superior planets are those farther from the Sun than the Earth (Mars, Jupiter, Saturn, Uranus, and Neptune). Astronomers describe the position of these planets relative to the Earth using the following terms.<\/p>\n\n\n\n