The angle between two planets, when it matches a measure held to be significant.
Two bodies 90° apart are in square, 120° apart in trine, and so on. Aspects are the heart of interpretation: they say how the parts of a person cooperate or obstruct one another. A chart with many tight aspects is more «loaded» than one with few and wide ones.
Where the aspect angles come from
The major aspects come from dividing the circle of the zodiac by small whole numbers. Divide it by two and you get the opposition, 180°; by three, the trine, 120°; by four, the square, 90°; by six, the sextile, 60°. Add the conjunction, 0°, where two planets overlap. These are known as the Ptolemaic aspects, after the ancient astronomer Ptolemy, and they are the five SideraMea calculates in your chart.
There are also minor aspects, such as the semi-sextile at 30° or the quincunx at 150°. Some astrologers use them and others leave them out: their influence is subtler, and they make the list much longer.
Flowing aspects and challenging aspects
Traditionally, trines and sextiles are seen as flowing aspects: the two planets work together without friction. Squares and oppositions are challenging aspects that ask for an adjustment, a choice, an effort. The conjunction is a case of its own, since its tone depends on the planets involved.
This is not a split between "good" and "bad". A chart full of trines can describe talents that are never put to the test, while a square handled well is often where real skill is built. When you look at an aspect, first ask which parts of you it brings into conversation, and only then what kind of conversation it is.
Frequently asked questions
How do you read aspects in a birth chart?
Start with the planets involved: each stands for a function, such as affection for Venus or drive for Mars. Then look at the type of aspect, which describes how those two functions meet. Finally check the orb, which shows how close the link is. Aspects with the smallest orbs are the ones to read first.
What does an unaspected planet mean?
A planet that forms no major aspect within orb is called unaspected. In astrology it is often read as a function that works on its own: it may stay in the background, or express itself in a pure, slightly detached way, apart from the rest of the personality. Whether a planet counts as unaspected also depends on the orbs used.
What is the difference between natal aspects and transit aspects?
Natal aspects are the ones between the planets in your own chart, fixed at the moment of birth. Transit aspects form between today's planets and those in your chart: they come and go, and are read as the periods when a part of your natal chart is switched on. That is why they use tighter orbs.
See it in your own chart
Calculating your birth chart is free: wheel, planets, houses, aspects and a first reading. All you need is your date, time and place of birth.