Syzygy (astronomy)
Encyclopedia
In astronomy
, a syzygy is a straight line configuration of three celestial bodies in a gravitational system. The word is usually used in reference to the Sun
, the Earth
and either the Moon
or a planet
, where the latter is in conjunction or opposition. Solar
and lunar
eclipse
s occur at times of syzygy, as do transits
and occultation
s. The term is also applied to each instance of new moon
or full moon
when the Sun and Moon are in conjunction or opposition, even though they are not precisely on one line with the Earth.
The word syzygy is often loosely used to describe interesting configurations of planets in general. For example, one such case occurred on March 21, 1894 at around 23:00 GMT, when Mercury
transited the Sun as seen from Venus
, and Mercury and Venus both simultaneously transited the Sun as seen from Saturn
. It is also used to describe situations when all the planets are on the same side of the Sun although they are not necessarily found along a straight line, such as on March 10, 1982.
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...
, a syzygy is a straight line configuration of three celestial bodies in a gravitational system. The word is usually used in reference to the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
, the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
and either the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
or a planet
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...
, where the latter is in conjunction or opposition. Solar
Solar eclipse
As seen from the Earth, a solar eclipse occurs when the Moon passes between the Sun and the Earth, and the Moon fully or partially blocks the Sun as viewed from a location on Earth. This can happen only during a new moon, when the Sun and the Moon are in conjunction as seen from Earth. At least...
and lunar
Lunar eclipse
A lunar eclipse occurs when the Moon passes behind the Earth so that the Earth blocks the Sun's rays from striking the Moon. This can occur only when the Sun, Earth, and Moon are aligned exactly, or very closely so, with the Earth in the middle. Hence, a lunar eclipse can only occur the night of a...
eclipse
Eclipse
An eclipse is an astronomical event that occurs when an astronomical object is temporarily obscured, either by passing into the shadow of another body or by having another body pass between it and the viewer...
s occur at times of syzygy, as do transits
Astronomical transit
The term transit or astronomical transit has three meanings in astronomy:* A transit is the astronomical event that occurs when one celestial body appears to move across the face of another celestial body, hiding a small part of it, as seen by an observer at some particular vantage point...
and occultation
Occultation
An occultation is an event that occurs when one object is hidden by another object that passes between it and the observer. The word is used in astronomy . It can also refer to any situation wherein an object in the foreground blocks from view an object in the background...
s. The term is also applied to each instance of new moon
New moon
In astronomical terminology, the new moon is the lunar phase that occurs when the Moon, in its monthly orbital motion around Earth, lies between Earth and the Sun, and is therefore in conjunction with the Sun as seen from Earth...
or full moon
Full moon
Full moon lunar phase that occurs when the Moon is on the opposite side of the Earth from the Sun. More precisely, a full moon occurs when the geocentric apparent longitudes of the Sun and Moon differ by 180 degrees; the Moon is then in opposition with the Sun.Lunar eclipses can only occur at...
when the Sun and Moon are in conjunction or opposition, even though they are not precisely on one line with the Earth.
The word syzygy is often loosely used to describe interesting configurations of planets in general. For example, one such case occurred on March 21, 1894 at around 23:00 GMT, when Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
transited the Sun as seen from Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...
, and Mercury and Venus both simultaneously transited the Sun as seen from Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...
. It is also used to describe situations when all the planets are on the same side of the Sun although they are not necessarily found along a straight line, such as on March 10, 1982.