Moon and Venus in western dusk October 2
Image Credit: Pitel. Some rights reserved.
October 2, 2008.
Look westward after sunset today – in the general direction of the sunset – to catch the waxing crescent moon and dazzling planet Venus in evening twilight.
These are nighttime’s two brightest lights, and they can be seen this early evening from everywhere on Earth except far northern latitudes. But even for us at mid-northern latitudes – here in the U.S. – you’ll need an unobstructed western horizon to catch the moon and Venus after sunset. They’re both bright so should be easy to see. But they’re not because, from our part of the world, the moon and Venus appear close to the western horizon at dusk. They set soon after the sun.
From the southern hemisphere, the moon and Venus stay out longer after the sun goes down. This is a seasonal difference. It’s early fall now in this hemisphere, when evening planets near the sunset are likely to be buried in the haze along the western horizon. Meanwhile, in the southern hemisphere now, it’s early spring. And springtime planets in the sun’s direction at dusk tend to stay out longer after dark.
It’s all because we live on a world that tilts on its axis. And by the way, the planet Mars is in the west after sunset too, but it’s far across the solar system now – faint – and not very noticeable from anywhere on Earth.
At latitudes close to the Arctic Circle, the ecliptic – or path of the sun, moon and planets – encircles the horizon at sunset. As the early autumn sun sets over the Arctic Circle, the waxing crescent moon and Venus pretty much set with the sun.
At mid-southern latitudes – like in Australia – these early spring sunsets find the ecliptic at a steep angle to the western horizon. There, the lunar crescent, Venus – and even the planet Mars – stay out till after dark.
