Sunday, April 11, 2010

Lonely Venus

If you look to the west around the time the Sun sets, you might have noticed something very bright and very alone.

It isn't the ISS, a meteor coming to destroy our planet (I hope) or a UFO. It's the planet Venus.
Venus is incredibly bright with an apparent magnitude of −3.8 to −4.6 (-3.92 right now) and it easily outshines all the stars. When at its brightest it is even visible during the day.
Venus follows the Sun a bit closer than we do (at around 0.7 AU or 100 million kilometres) and so it is mostly visible around sunrise/sunset (depending on it's position relative to the Sun and the Earth).

If we turn up the brightness a bit (the pictures were taken about about 2115 CET) you can really see how alone Venus it at dusk. No stars become visible.

But you might notice something else close to Venus (I've circled it below).

Later in the evening (around 2145 CET) as the sky darkens further, the companion becomes more easily visible in the sky (you might need to click the picture to see the bigger version)

So what might that be? It's faint, but doesn't twinkle like a star (you obviously can't see it in the pictures). It doesn't move either.

It's Mercury of course. The smallest planet in the solar system and the one closest to our star.
Mercury can be hard to find as it follows the Sun around very closely (at around 0.3-0.45 AU or 45-70 million kilometres) and the light from the Sun usually drowns out the light from the small planet.

But you can see it now. Go outside at dusk and find Venus (the next picture was taken around 2200 CET). Bring a pair of binoculars or similar equipment and have a look at the sky. Once you've found Venus, search a bit to the right and you might find Mercury (click the picture to see it more clearly).

According to the Bad Astronomer, Mercury is fading fast so you will have to hurry if you want a good look at it.