Venus is our Christmas Star

The planet Venus is making its way into the evening sky. Throughout December it is quite low in the south-western sky just after sunset, though getting higher every night. To begin with you’ll need a good low horizon in that direction, but by the end of December it’s already about 14º altitude at the end of civil twilight and easy to spot as the brightest object in the twilight.

On 28 and 29 December the crescent Moon is nearby, providing two good chances to try out that new camera you got for Christmas!

Venus over the rooftops, 4 December 2019. Photo: Robin Scagell

Keep an eye on what’s happening, because Venus is going to become a spectacular evening star, much higher in the evening twilight, throughout the spring of 2020, and many non-astronomers will spot it and ask what it is.

Currently the planet is on the far side of the Sun, moving around its orbit, which lies inside that of Earth. Through a telescope it appears as a small disc, 12 arc seconds across. Because of its low elevation above the horizon, the image will appear blurry and unstable as a result being viewed through a long path of our atmosphere. This will also cause the light from Venus to be split into rainbow colours – pretty, but with no detail on the planet itself.

During the first part of 2020 the planet gets closer, moving away from the Sun as it does so, and will appear higher in the sky. By March it will be twice its current diameter and will show a distinct phase, and by May it will be very close and bright, but again low down in the twilight.