Conjunctions, Oppositions and Elongation Planets Conjunctions, Oppositions and Elongation

Planets without a telescope look just like stars Except, they move relative to the stars

Conjunctions and Oppositions In a Conjunction the celestial objects appear near each other in the sky In an Opposition the objects appear in opposite directions, (If only one object is mentioned the other is assumed to be the Sun!) These occur because the earth and the celestial objects line up (Please copy all diagrams)

Superior Planets Superior Planets orbit farther from the Sun than Earth. They can be in conjunction or opposition. They are in Conjunction when they are on the other side of the Sun. As far away as they can be from Earth. They are in Opposition when the Earth is between the Superior Planet and the Sun. It is then that they are nearest to the Earth, and thus are the brightest.

Inferior planets are never in opposition! Mercury and Venus are inferior planets, they orbit closer to the Sun than Earth Inferior Planets can have 2 kinds of Conjunctions with the Sun An Inferior Conjunction is when it is between the Earth and the Sun. This is when the planet is closest to the Earth, and thus is brightest A Superior Conjunction is when it is directly on the other side of the Sun Inferior planets are never in opposition!

Elongation The elongation of a planet is its distance from the sun in degrees Superior planets can have any elongation from 0 to 180° Inferior planets cannot. The maximum elongation of Venus is 46° The maximum elongation of Mercury is 28°

Morning and Evening Stars Sometimes an inferior planet will rise and set before the Sun. You can only see it in the morning before Sunrise …A “morning star” At other times it will rise and set later than the Sun. It can then be seen only in the evening for a short time after sunset … an “evening star”

Synodic Period The Synodic Period of a planet is the time between two oppositions or conjunctions of the same type. This is not the same as the planet’s year… Because the Earth is moving too!