Heliacal rising

The heliacal rising (/hɪˈlaɪəkəl/ hih-LY-ə-kəl) or star rise of a star occurs annually, or the similar phenomenon of a planet, when it first becomes visible above the eastern horizon at dawn just before sunrise (thus becoming "the morning star"), after it has spent a season behind the sun rendering it invisible. Historically, the most important such rising is that of Sirius, which was an important feature of the Egyptian calendar and astronomical development. The rising of the Pleiades heralded the start of the Ancient Greek sailing season, using celestial navigation.

Heliacal rising

The heliacal rising (/hɪˈlaɪəkəl/ hih-LY-ə-kəl) or star rise of a star occurs annually, or the similar phenomenon of a planet, when it first becomes visible above the eastern horizon at dawn just before sunrise (thus becoming "the morning star"), after it has spent a season behind the sun rendering it invisible. Historically, the most important such rising is that of Sirius, which was an important feature of the Egyptian calendar and astronomical development. The rising of the Pleiades heralded the start of the Ancient Greek sailing season, using celestial navigation.