Any two planets are at an angle from each other, as well as from the Midheaven, Ascendant, or Moon’s Node. Let’s say that Venus is at 2 degrees Aries and Pluto is at 22 degrees Gemini. The planets are 80 degrees apart.
When two planets are at specific angles from each other, like 60, 90, 120, or 180 degrees, these are known as aspects. I mention these particular angles because they are the most commonly used aspects:
60 degrees is a sextile, in other words 1/6 of the circle.
90 degrees is a square, in other words 1/4 of the circle.
120 degrees is a trine, or 1/3 of the circle.
180 degrees is an opposition — two planets are on opposite sides from each other.
There is also the conjuction, where two planets are approximately in the same place.
How close do these angles have to be to be valid? Astrology uses areas of leeway called orbs, where, if a aspect is within the orb it has a level of validity. Of course, the closer the better — like a 61-degree sextile is stronger than a 63-degree sextile, but even the 63-degree sextile is generally (barely) within the orb, depending on any given astrologers’ opinion. It’s common for orbs for sextiles and squares to be 3 or 4 degrees.
Trines, oppositions, and conjuctions, on the other hand, might have allowable orbs of 6 degrees. David Cochrane, a harmonic and vibrational astrologer, believes that the conjuction’s orb is 16 degrees!
(Vibrational astrology is a fascinating and keenly accurate branch of astrology, so feel free to look at Cochrane’s many videos on that and other subjects).
So, what does a sextile, square, trine, opposition, or conjuction really mean?
In classical astrology, sextiles, oppositions and trines are favorable, while squares and oppositions are challenging. How so? I’ll attempt to distill some astrological knowledge here:
Conjuction — two or more planets in the same place are the strongest of the aspects. These are planets in unity, operating as one. Say, someone has Moon and Mercury both conjunct in Capricorn. This tends to conjoin both their mental and emotional sides together, in one of the most disciplined and practical sides. Arguably Mercury would be more compatible with Capricorn, so perhaps their head rules their heart in some cases. This lends it also to good intuition and understanding.
Trine — planets 120 degrees apart. This generally lends itself to a great ease or support of any issue that has to do with the two planets. A grand trine are three planets, each 120 degrees from each other — creating the image of a triangle in the chart wheel! These are very favorable communications pertaining to the three planets involved. Favorable, yes, but too many trines can lead to a certain laziness. Trines are also notable as the two planets are almost always in the same element (example: having Mars at 26 degrees Aquarius, an air sign, and Jupiter at 29 degrees Libra, also an air sign.)
Sextile — planets 60 degrees apart. These are also favorable, harmonious and offer opportunity, though unlike the trine they require some work to realize their benefits. They are almost always either yang (like Libra and Sagittarius), or yin (like Taurus and Cancer).
I say “almost always” in these two situations because with orbs, the two planets may be in dissimilar elements. Imagine Jupiter being 29 degrees Libra and Mercury being 1 degree Capricorn. This counts as a sextile but notice, the signs are three apart. This aspect is real, but not as powerful as one that’s two apart, like Pluto being 27 degrees Virgo and Neptune being 29 degrees Scorpio, even though the orb in both cases is two degrees. Orbs can create this situation when the planets are close to cusps in any of the types of aspects, but it is uncommon.
Square — planets 90 degrees apart. These are challenging, some astrologers will say extremely challenging. They signify issues of tension between the two planets. If the tension between the two planets is resolved, it can offer great benefits — adding character. There is a pattern called a T-square, with two planets 180 degrees apart (thus an opposition), and a planet 90 degrees from both. If resolved, these are quite powerful, although it’s the “missing planet” (the point opposite the planet in between) that often is the focus of the challenge. So, having Midheaven at 28 degrees Leo, Mars at 26 degrees Aquarius, and Neptune at 29 degrees Scorpio has “issues” with the point of the chart as 28 degrees Taurus, where there is no planet in this case.
Opposition — planets that are 180 degrees apart. These pertain to two energies opposite each other, that pull on each other. Imagine having Jupiter opposite Saturn in a chart. The expansion and fortune of Jupiter is countered by the contraction and difficulty of Saturn. Sometimes the person can go back and forth between both. These are best handled through conscious awareness. Four planets, all at 90 degree intervals, create four squares and two oppositions and are known as a “grand cross,” which is quite challenging but if resolved can be very powerful.
There are more minor aspects, including:
Semi-Sextile — two planets 30 degrees apart. Favorable, but not as much so as a sextile.
Quincunx — two planets 150 degrees apart. Usually mildly challenging A planet with two quincunxes creates an additional sextile and is known as a Yod.
Quintile and BiQuintile — this is when one separates a circle into 5 parts, each 72 degrees apart. A quintile is 72 degrees and a biquintile is 144 degrees. Both are favorable, genuinely lending to special talents. A quintile pattern can take the whole circle, like Venus at 7 degrees Sagittarius, Pluto at 27 degrees Virgo, and Saturn at 2 degrees Taurus. Saturn is biquintile both Venus and Pluto, who are quintile each other.
Semi-Square (45 degrees) and Sesquiquadrate (135 degrees). These tend to be somewhat challenging like a square but are not as strong.
Other aspects are the Septile (about 51 degrees, 1/7 of the circle), the Novile (40 degrees), and really any division of the circle. Dividing the circle into more portions gets us into the realm of Vibrational, or Harmonic, astrology.
Most of these minor aspects have smaller orbs — the Quintile’s being 3 degrees, and others being slightly less.
You can see examples of the aspects on the Birth Chart page.