The assignments of the ruling planets appear to be based upon the Northern Hemisphere seasons, as the sun (Sol) and the moon, the principal bearers of light and heat, were awarded to Leo and Cancer, respectively, since the months the sun passed through these signs (in ancient times) were the warmest and had the longest days.
Conversely, Saturn, the most distant (and hence the "coldest") of the planets known to ancients, was accorded the rulership of Aquarius and Capricorn, the signs opposite Leo and Cancer, respectively.
Jupiter, being next farthest away, was given the signs on either side of Aquarius and Capricorn (Pisces and Sagittarius), and Mars, next in order, received the next two (Aries and Scorpio).
provided a dilemma for astrologers, which most eventually resolved by a consensus declaring Uranus to be Aquarius' ruling planet while assigning Neptune to Pisces and later, Pluto, considered the higher octave of Mars, was given to Scorpio.
Although the status of Ceres has not been conclusively decided at the moment in astrology, it has been suggested as the ruler of Virgo or Taurus.
Some modern astrologers assign what is called "natural" rulership of each house of the horoscope to a different planet, in the same way as the zodiac signs are said to have rulers.
Ultimately, intercepted Aquarius and Uranus will express itself but be mediated strongly through Capricorn and its ruler, Saturn.
Significant disagreement exists within the Western astrological community about some of the signs that are often still said to share rulers which is a problem that is taking time to resolve.
This process continues until there is a final disposition (sign in its rulership) or it circles in a never-ending chain of command.