Which planets can two Sun signs actually share?

Each row is one pairing of Sun signs, such as Taurus and Leo. The shares answer one question: if you take a person born with the first Sun sign and a person born with the second, how often does a given fact hold? 42 of the 78 pairings can never share a Mercury sign, because the two Suns are too far apart for Mercury to reach a common sign, and 18 can never share a Venus sign. At the other end, two Sagittarians share a Mercury sign in 42.9% of pairs, the highest figure in the table.

Some quantities barely move between pairings. Mars keeps its own timetable, so a shared Mars sign runs from 6.4% to 11.5% across all 78. A close Venus–Mars contact between the two charts (conjunction, trine or opposition within 6 degrees, either way round) runs from 20.7% to 28.5%. The Moon moves through every sign each month, so two people share a Moon element in 25.0% of pairs whatever their Sun signs. Those flat results are findings too: a Sun-sign pairing tells you very little about Mars or the Moon.

Apparent geocentric ecliptic longitudes of date for the Sun, Moon, Mercury, Venus, Mars, Saturn, Uranus and Neptune were taken from NASA JPL's DE442 ephemeris through Skyfield 1.53, every 6 hours from 1 January 1950 to 31 December 2009 (87,660 instants). Each instant stands for one possible birth. Signs are tropical, 30 degrees each from 0 Aries, which is the zodiac Shymea uses throughout (methodology).

A pair is one birth with the first Sun sign and one with the second, drawn independently. Every share is taken over all such combinations rather than a random sample: sign and element matches are products of the two per-sign distributions, and angular quantities (how far apart the Suns are, whether one person's Venus aspects the other's Mars) come from cross-correlating 0.1-degree longitude histograms. The only approximation is that 0.1-degree binning. Nothing else goes in, so anyone with the DE442 file can recompute every figure on this page.

• Same Mercury, Venus or Mars sign: both people have that planet in the same zodiac sign.
• Same Mercury element: both Mercury signs share an element (Fire, Earth, Air or Water) even if the signs differ.
• Venus–Mars link: one person's Venus within 6 degrees of a conjunction, trine or opposition to the other person's Mars, in either direction.
• The CSV adds more: Sun separation ranges, the share of pairs within 3 and 8 degrees of the exact angle between the signs, out-of-sign aspects, each planet in the other person's Sun sign, and Mercury–Sun and Venus–Sun contacts.

Births are treated as spread evenly through 1950–2009, with no allowance for birth seasons or for the age gap between partners, so the shares describe the sky, not any real population of couples. Saturn, Uranus and Neptune are used only in the page-specific extras, because whether two people share them depends on how far apart in age they are. No compatibility score is computed and none should be read into these numbers: they say how often a placement occurs, not whether a relationship works. The byline is Shymea Editorial.