Ketu does not rule any zodiac
Ketu (South Lunar Node), just like Rahu, is also an imaginary planet, a node. It is positioned at the meeting point of the earth's trajectory around the Sun and the Moon's trajectory around the Earth meet. It is said according to Indian mythology that Ketu represents the tail of demon(just like Rahu represents the head). Both the planets are the parts of the same danava (demon) but are 180 degree apart from each other.
When the Ketu, the Sun and the Moon lie in the same zodiac longitude, lunar eclipse takes place. In certain ways Ketu resembles Mars but many times it activates only the negative side of Mars.
Rahu and Ketu are the two mysterious forces and show in the birth chart both karmic and spiritual influences. Ketu is also not a real luminary and therefore doesn't rule any zodiac sign.
Note : On Ketu Dasha or the position of Ketu depends the luck of a person.
