Why can’t we continually see Venus?
It’s our next door neighbour, so why can’t we see it every night?
The crescent Moon and, to its left, planet Venus, make for beautiful scenery alongside the dome of one of the VLT’s Auxiliary Telescopes seen in the foreground.
The main reason we don’t see as much of Venus as we do of the outer planets is due to the fact that Venus orbits so closely to the Sun and, when it sets, Venus will set shortly afterwards. However its proximity to the Sun does mean we can often see it in daylight!
In addition, in order to see a planet, we rely on light from the Sun reflecting off the planet and back towards us. Since at night observers are on the side of the Earth facing away from the Sun, they are generally looking in the opposite direction to the inner planets. There is only a limited set of positions in which the Sun, Venus and the Earth can line up allowing reflected light from Venus to reach an observer on the night side.
Image courtesy of ESO
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