Sothis

Sirius (Sothis in Greek, Sopdet in Egyptian) is the brightest star in the sky. It is identified with Isis in many Egyptian texts. The first appearance of Sirius in the sky announces the annual flooding of the river Nile.

Sirius is called The Dog Star; it is the eye of the dog in the constellation Canis Major (Latin for the greater dog).

The Wikipedia article about Sothis contains astronomical and mythological information.

Sirius has its fearsome side. Its rising is also associated with seasons of illness, heat, and destruction..

It is not a single star, but a binary star system.

The Tour Egypt website also has a good article; so does Crystalinks.