The band of sky along the ecliptic where the Sun, Moon and planets move. The ecliptic actually crosses 13 constellations, including Ophiuchus. Astrology’s “signs” no longer match the constellations, shifted by precession: astrology is not a science.
Related terms
- Ecliptic
The Sun’s apparent path among the stars over the year, mirroring the plane of the Earth’s orbit. It is tilted by 23.4° to the celestial equator. The Moon and planets always stay close to it, which helps to recognise them.
- Constellation
One of the 88 regions that have officially divided the sky since 1922–1930, each with its own borders, like counties on a map. The stars of a constellation are often unrelated, at very different distances. Their Latin names are used to label stars, such as Alpha Lyrae for Vega.
- Precession
The Earth’s axis slowly sweeps out a cone, like a spinning top, in about 26,000 years. The celestial poles therefore wander among the stars: in about 12,000 years Vega will be near the north pole. Star coordinates slowly change, which is why an epoch such as J2000 is given.
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