Opposition (planets)

As opposition is called in astronomy the aspect in which two celestial bodies of 180 degrees are from Earth viewed at an angular distance (elongation ) to each other. Interested in doing only the opposition of a celestial body to the sun in most cases ( as a second celestial body ), because the former then the night can be seen on the sky and is at its highest at midnight on the horizon.

Is about the Moon in opposition to the Sun, so we have a full moon. Celestial bodies that orbit as the inferior planets Mercury and Venus within the Earth's orbit the sun, however, can never be in opposition to the Sun and therefore always only in the evening or morning sky, but not visible during the whole night.

Time near to the opposition of a celestial body in relation to the sun the least Erdabstand is regularly achieved, which is for ground-based observations of course an advantage. Because of the eccentricity of the planetary orbits, however, this slightest Erdabstand is frequently not achieved exactly at opposition time point, the difference occurring a few days but is usually of no practical significance.

If two celestial bodies at almost the same time in opposition to the Sun, so it may be a so-called triple conjunction because of the apparent loop tracks ( opposition loop ) of the celestial bodies involved. Here, the two bodies meet three times at intervals of a few months.

Special forms of opposition

• Full moon
• Lunar eclipse