Starwatch: Venus and Jupiter to shine side-by-side at dusk

The two brightest planets meet this week in the western twilight sky. The chart shows the view looking west-northwest at 21:45 BST. No stars will yet be visible, but Venus and Jupiter will be brilliant against the darkening sky.The planets will be separated by about 1.5 degrees – about the width of three full moons. They will be low to the horizon, so you will need a clear sightline in their direction. If you can find a hill, that will help too.Venus is the easier of the two to spot. It is the brilliant “evening star”, blazing at a magnitude of about –4.0. Jupiter is fainter, but still bright at about magnitude –1.9. Both planets are currently situated in Gemini, the twins, although the stars of the constellation will only become visible as the sky darkens and the tableau slips even closer to the horizon. The constellation’s two brightest stars, Castor and Pollux, will be the first stars to shine through.Those with an excellent view of the western horizon stand a chance of seeing the inner planet Mercury too. It lies midway down the bodies of the twins. But it will be a race for the sky to darken enough before it disappears below the horizon.