It's just a phase

By Phil Plait | March 17, 2009 2:30 pm

If you go outside just after sunset and look west, you’ll see a brilliant white star hanging over the horizon. But that’s no star, that’s Venus. Right now Venus is incredibly bright, even brighter than it has been the past few weeks. That’s because it’s getting closer to the Earth as it rounds the Sun, about to pass us like one racecar whooshing past another.

If you think about it, Venus is almost directly between us and the Sun right now. That means we’re looking mostly at its unlit half; the lit half is facing the Sun, and we can’t see it. Or more accurately, we only see a little sliver of it, making Venus crescent-shaped. When Venus is on the other side of the Sun from us, we’re looking at the lit half, so it looks full.

The funny thing is, even though it’s a thin crescent right now, it’s a lot closer to us so it looks bigger. That’s why it’s brighter now; we’re actually seeing it occupy more real estate in the sky, so it’s really bright.

Crescent Venus from Some Canadian Skeptic

In fact, it’s so big that I just saw the crescent easily in my binoculars. And Steve, aka Some Canadian Skeptic, got a great shot of it using nothing more than a camera with a telephoto, as you can see in this picture here (click to embiggen).

Because Venus is close to us right now (about 45 million km or 27 million miles) it appears to be moving rapidly across the sky; every day you’ll see it getting lower in the sky, and in a few days it’ll be so low after sunset it’ll be lost in the glare. So take the chance now! Go out and take a look, because it’ll be a couple of months before it’s visible again… as a morning star in the east.

CATEGORIZED UNDER: Astronomy, Pretty pictures

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