Field guide · Reading the sky

Circumpolar

Close enough to the celestial pole that it never sets from where you are. It circles the pole all night, every night of the year.

Rule of thumb

Within your latitude of the pole

From the equator

Nothing is circumpolar

From the poles

Everything is

The sky seems to turn once a day around a point above the Earth’s pole. Stars near that point circle it without ever dipping below the horizon; they are circumpolar. Stars farther away rise and set.

Which stars qualify depends on your latitude: anything closer to the pole than your latitude is. From London the whole of the Big Dipper and Cassiopeia never set. From the North Pole every visible star is circumpolar; from the equator, none is.

The ancient Egyptians called the northern circumpolar stars “the imperishable ones” — the stars that never die — and aligned passages in the pyramids towards them.

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