Stellium in astrology: a cluster of planets in one sign or house

A stellium is a cluster of several planets in one sign of the zodiac or in one house of the chart. Strictly speaking it is not an aspect and not a figure drawn with lines, like a T-square or a yod. It is a matter of density: many functions of the chart gathered on a short stretch of the circle. That is why it is discussed alongside configurations even though it works differently. There is no single definition, and that is the main difficulty: the same group of planets is a stellium for one astrologer and not for another.

What a stellium is and where the word comes from

The word comes from the Latin stella, star. Older books also use the term satellitium for the same thing. The idea is simple. When three or four planets gather in one sign, that sign speaks louder in the chart than it could through the Sun or the Ascendant alone. When they gather in one house, that area of life takes a disproportionate share of attention.

On the wheel a stellium is obvious at a glance: one part of the chart is packed with glyphs while the rest is empty. Even a beginner notices it before any aspect.

How many planets count

This is where astrologers disagree most.

• Three planets. The most common modern threshold. Three planets in one sign already shift the balance of elements and modalities in a chart.
• Four planets. A stricter threshold that some authors prefer. Their argument: three planets in one sign are common, especially when Mercury and Venus are among them, since neither ever strays far from the Sun. A real cluster, in this view, starts at four.

The Sun and Moon are normally counted as full members of a stellium. The lunar Nodes, Chiron, Lilith, asteroids and other points are left out by most astrologers: they are not planets, and the chart's balance does not change without them. The Ascendant or Midheaven inside a group adds weight to it, but on their own they do not make a stellium either. If a group reaches three only thanks to the Node, it is more honest to call it two planets and the Node than to call it a stellium.

Sign stellium and house stellium

A stellium in a sign amplifies the qualities of the sign itself: its element, its modality, its style of acting. With three planets in Virgo, the person's thinking, feelings and will all pass through attention to detail and practical checking. The whole chart takes on a Virgo tone even if the Sun is elsewhere.

A stellium in a house speaks about an area of life rather than a style. Three planets in the 10th house focus energy on career and public role; in the 4th, on family and home. A house stellium requires an accurate birth time, since without it the house cusps are unknown.

Sign and house stelliums often coincide, but not always. A group in one sign can stretch across two houses, and a group in one house can span two signs. In that case each picture is described separately.

Out-of-sign stelliums

Imagine planets at 27° Aries, 2° Taurus and 5° Taurus. Only 8° separate the outer two, they are tightly linked by conjunctions, and yet they sit in two signs. By the sign-based definition this is not a stellium: one planet in Aries, two in Taurus. By the conjunction-based definition it is a tight cluster of three planets.

Most astrologers accept such a group but read it as mixed: part of its energy carries the fiery tone of Aries, part the earthy tone of Taurus. It is sometimes called an out-of-sign stellium, by analogy with an out-of-sign aspect.

How a stellium differs from a conjunction

A conjunction is an aspect between two planets with a specific orb. A stellium is a group, and there are two ways to define it.

• Strict definition. All the planets in the group are linked by conjunctions, either directly or as a chain: the first conjunct the second, the second conjunct the third. A stellium is then an extended conjunction, and its planets merge into one shared impulse.
• Loose definition. It is enough for three or more planets to stand in one sign (or one house), whatever the distance between them. A stellium is then mainly an emphasis on a sign, not a fusion of functions.

The difference matters. Planets at 1° and 28° of the same sign belong together under the loose definition, yet almost 30° separate them and they form no aspect at all.

How to read a stellium

• Sign and house. What is amplified: the style (sign) and the area of life (house).
• The ruler of the sign. The planet that rules the stellium's sign becomes important for the whole chart, because the entire group works through it. Its position shows where the cluster's energy is directed.
• The tightest pair. Inside the group, look for real conjunctions. They form the core; the other planets add to it.
• What is empty. A stellium means fewer planets elsewhere. An element or modality with no planets at all is part of the picture too.

Example: the Cancer group in Donald Trump's chart

In Donald Trump's chart three planets stand in Cancer: Mercury at 8°51′, Saturn at 23°48′ and Venus at 25°44′. In the Placidus calculation all three fall in the 11th house. Under the loose definition this is a stellium both by sign and by house.

Under the strict definition the picture changes. Venus and Saturn form a conjunction with an orb of 1°55′. Mercury sits almost 15° from Saturn and almost 17° from Venus, and forms no conjunction with either. By the strict standard, then, this is one conjunction of two planets plus a third planet in the same sign: a group in a sign rather than a stellium. It is a good illustration of how far the two definitions can drift apart on the same chart.

How tradition reads the group: Cancer is a cardinal water sign, so the emphasis falls on protecting one's own circle, loyalty and memory of the past. The core of the group is Venus with Saturn: attachment that looks for reliability and holds on for a long time. The ruler of Cancer, the Moon, is in Sagittarius, and it is through the Moon that this energy finds its way out.

The same chart has another cluster that shows the question of the Node in practice. In Gemini stand Uranus at 17°53′, the North Node at 20°48′ and the Sun at 22°55′. Without the Node these are two planets about 5° apart; with it, three points within about 5°. Those who count the Node see a cluster here, those who do not see a pair. For more on how wide a conjunction can be before it stops counting, see the page on orbs.

In celebrity charts

Three or more planets in one sign.

• Andriy Shevchenko: Sun, Mars and Pluto in Libra
• Angela Merkel: Sun, Mercury, Jupiter and Uranus in Cancer
• Barack Obama: Sun, Mercury and Uranus in Leo

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