A.U

Definition

A.U. most commonly stands for astronomical unit, a standard measure equal to the average distance between Earth and the Sun—about 149.6 million kilometers or 93 million miles. Astronomers use it to express distances within a planetary system more conveniently than miles or kilometers.

Astrological Meaning

In astrology, A.U. belongs mainly to the astronomical framework behind chart calculation rather than to symbolic interpretation. It can describe the scale of planetary distances, but astrologers generally interpret a planet through its zodiacal position, house placement, aspects, motion, and relationship to the chart as a whole. A planet’s distance in astronomical units does not usually receive a separate natal meaning. The abbreviation should also be read in context, especially in older tables or specialized reference works, where conventions may differ.

Why It Matters

Understanding A.U. helps distinguish measurable astronomy from astrology’s symbolic methods. Accurate knowledge of planetary positions and cycles supports the construction of natal charts, transits, and other astrological techniques, even when the physical distance itself is not interpreted. Recognizing the term can also make ephemerides, technical notes, and discussions of planetary motion easier to follow. When A.U. appears in an unfamiliar historical source, checking that source’s abbreviations is preferable to assuming a universal astrological definition.

Related Encyclopedia Entries

• Traditional Astrology
• Astrological Terminology
• Natal Chart