Multiple realities
(covers information from several alternate timelines)

Ceti Alpha was the primary of the Ceti Alpha system.

In 2165 in an alternate timeline where the Xindi destroyed Earth, Yerdrin Lek hid his ship just outside the chromosphere of Ceti Alpha, after he tailed Doctor Phlox to the system. Nevertheless, he was discovered when Enterprise NX-01 picked up an intermittent duranium signature. (ENT: "Twilight")

According to Star Trek: Star Charts ("United Federation of Planets II") and Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), Ceti Alpha was located in the Beta Quadrant. It was a K-class star.