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The superior planets, orbiting outside the Earth's orbit, do not exhibit a full range of phases since their maximum phase angles are smaller than 90°. Mars often appears significantly gibbous, it has a maximum phase angle of 45°. Jupiter has a maximum phase angle of 11.1° and Saturn of 6°, [1] so their phases are almost always full.
Diagram showing the eastern and western quadratures of a superior planet like Mars. In spherical astronomy, quadrature is the configuration of a celestial object in which its elongation is a right angle (90 degrees), i.e., the direction of the object as viewed from Earth is perpendicular to the position of the Sun relative to Earth.
For some objects, such as the Moon (see lunar phases), Venus and Mercury the phase angle (as seen from the Earth) covers the full 0–180° range. The superior planets cover shorter ranges. For example, for Mars the maximum phase angle is about 45°. For Jupiter, the maximum is 11.1° and for Saturn 6°. [1]
Animation of the Moon as it cycles through its phases. The apparent wobbling of the Moon is known as libration. The Moon is in synchronous rotation, meaning that it keeps the same face toward Earth at all times. This synchronous rotation is only true on average because the Moon's orbit has a definite eccentricity.
In the reference frame of the Earth, where the terms were originally used, the inferior planets are Mercury and Venus, while the superior planets are Mars, Jupiter, Saturn, Uranus and Neptune. Dwarf planets like Ceres or Pluto and most asteroids are 'superior' in the sense that they almost all orbit outside the orbit of Earth.
The Moon then wanes as it passes through the gibbous moon, third-quarter moon, and crescent moon phases, before returning back to new moon. The terms old moon and new moon are not interchangeable. The "old moon" is a waning sliver (which eventually becomes undetectable to the naked eye) until the moment it aligns with the Sun and begins to wax ...
The Moon is Earth's only natural satellite. It orbits at an average distance of 384,400 km (238,900 mi), about 30 times the diameter of Earth. Tidal forces between Earth and the Moon have synchronized the Moon's orbital period (lunar month) with its rotation period at 29.5 Earth days, causing the same side of the Moon to always face Earth.
The apparent brightness of Mercury as seen from Earth is greatest at phase angle 0° (superior conjunction with the Sun) when it can reach magnitude −2.6. [14] At phase angles approaching 180° ( inferior conjunction ) the planet fades to about magnitude +5 [ 14 ] with the exact brightness depending on the phase angle at that particular ...