The brightest "star" at dusk: why is it never out at midnight?

Venus circles the Sun at about 0.7 times the Earth–Sun distance. Seen from Earth, it only swings back and forth to the left or right of the Sun, and even at its farthest it is only about 47 degrees away from it. To be high in the sky at midnight, a planet has to sit on the opposite side of the sky from the Sun, and Venus can never get there.

So when Venus sets later than the Sun, you see it in the western sky in the evening, and when it rises earlier than the Sun, you see it in the eastern sky at dawn. Either way, you can watch it for three or four hours at most after sunset or before sunrise. Mercury also orbits inside Earth's orbit and behaves the same way, but it stays within about 28 degrees of the Sun, so it is much harder to find than Venus.

Korean has separate names for Venus: "saetbyeol" (샛별) for Venus in the dawn sky, and "gaebap-baragi" (개밥바라기) for Venus in the evening. Gaebap-baragi means roughly "the star that comes out when the dog waits for its supper." The ancient Greeks also thought the morning star and the evening star were two different stars and gave them separate names. In fact, it is the same Venus moving between dawn and dusk over time, which is how it earned two names.

Venus stands out so much because its thick clouds reflect sunlight very well and because it is the planet that comes closest to Earth. After the Sun and the Moon, it is the brightest thing in the night sky, appearing roughly ten to twenty times brighter than Sirius, the brightest star.

Because it is so bright and twinkles so little, people often mistake it for an airplane or even a UFO. But if it stays in place for several minutes and slowly sinks along with the sky where the Sun went down, it is very likely Venus.

To find it, look low in the western sky about 30 minutes after sunset, or in the eastern sky about an hour before sunrise. For a few weeks when Venus lines up almost in the same direction as the Sun, though, it is lost in sunlight and can't be seen at all. This arrangement repeats about every 584 days.