Starwatch: Venus, Mars, Jupiter and Saturn reveal the ecliptic

Four naked-eye planets will appear in line, showing solar system's plane

This week we can observe four of the five naked-eye planets (Venus, Mars, Jupiter and Saturn, but not Mercury) with the added bonus of a young moon, too. In doing so, we will be able to discern the ecliptic: the plane of the solar system, which defines the path in the sky that the sun, moon and planets all follow.

The chart shows a wide swathe of the sky, stretching from the south-east to south-west, as it will appear above London on 31 January at 6.45pm GMT. Starting at the western end of the panorama, a beautifully slender waxing crescent moon will be visible. Just 2.4 days old, only 6.2% of its visible surface will be illuminated.