Starwatch: Jupiter joins the half-moon in a sunset display

Starwatch chart 13 August 2018

There is a pretty pairing of celestial objects to be seen this Friday at sunset. The Moon will draw close to the bright planet Jupiter. The chart shows the view on 17 August, looking south-west at 21:00 BST. Giant Jupiter is the fifth planet from the Sun, and the first of the gas giants. It is around twelve times the diameter of the Earth and has a dense atmosphere, with storms as large as our entire planet. The Moon will be one day away from first quarter, and so half will appear to be illuminated. In another week’s time, the Moon will be nearing full. The conjunction happens in the faint constellation of Libra. If you keep watching that evening for another hour, you will see that Jupiter approaches the horizon and the sky gets noticeably darker. Those with a clear horizon may also be able to spot Zubenelgenubi, one of the brightest stars in Libra. Jupiter will be close to it that evening but much brighter. The star’s name means “southern claw” in Arabic, and indicates that it was once thought to be part of the neighbouring constellation Scorpius, rather than in Libra.