Heliacal rising

The heliacal rising (/hɪˈlaɪəkəl/, hi-LY-ə-kəl) of a star occurs annually when it first becomes visible above the eastern horizon for a brief moment just before sunrise, after a period of time when it had not been visible. Some stars, when viewed from a particular latitude on Earth, do not rise or set. These are circumpolar stars, which are either always in the sky, or never. For example, the North Star is not visible in Australia and the Southern Cross is not seen in Europe, because they always stay below the respective horizons.

Heliacal rising

The heliacal rising (/hɪˈlaɪəkəl/, hi-LY-ə-kəl) of a star occurs annually when it first becomes visible above the eastern horizon for a brief moment just before sunrise, after a period of time when it had not been visible. Some stars, when viewed from a particular latitude on Earth, do not rise or set. These are circumpolar stars, which are either always in the sky, or never. For example, the North Star is not visible in Australia and the Southern Cross is not seen in Europe, because they always stay below the respective horizons.