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Moving Day

March 24, 2017

Venus is losing its identity. After tonight, it will no longer be the “evening star.” Instead, it’ll be the “morning star,” as it crosses the line between Earth and the Sun.

This crossing is known as inferior conjunction, and it happens every 584 days — about 19 months. During that interval, the planet goes through a series of phases like the phases of the Moon.

At conjunction, Venus is “new” — the entire hemisphere that faces Earth is in the planet’s own shadow, so we’re looking at its nightside.

After conjunction, Venus becomes a thin crescent, which grows fatter as the weeks roll by. It’s during its crescent phase that Venus shines at its brightest. The planet is close to Earth then, so it forms a relatively large target in our sky. That proximity also means that more of the sunlight that Venus reflects into space reaches Earth. The combination makes the planet especially bright.

After that, Venus gets “fuller,” as sunlight illuminates more of its Earth-facing side. But it also moves farther away, so it doesn’t look as bright.

Venus is “full” at superior conjunction, when it lines up behind the Sun. After that, Venus begins to wane again as it once again prepares to cross between Earth and the Sun.

Venus is probably too close to the Sun for most of us to see it this evening. But it could be visible in the east shortly before sunrise tomorrow — and will definitely be putting in a great showing within a few days — as the “morning star.”


Script by Damond Benningfield

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