Starwatch: Mars and Saturn line up with the moon in the southern sky

This week the waxing Moon glides between Saturn and Mars in the low southern sky. Mars is the brighter and redder of the two planets. The chart shows the sky at 20:00 BST on 16 October 2018 when the Moon is roughly halfway between the two visible planets. The Moon will be at first quarter phase, when half the illuminated surface will be visible from Earth. While Mars and Saturn are the planetary stars of this show, on the 16th the Moon is actually aligned most closely with the dwarf planet Pluto, which sits in the sky just to the right of the Moon, in the direction of Saturn. But the far-off world is invisible to the naked eye, being thousands of times too faint to trigger our retina. Pluto itself is just two-thirds the diameter of the Moon, meaning that its surface area is just larger than that of Russia. The planet Saturn is 9.5 times wider than Earth, but 21 times wider when measured from one side of its expansive ring system to another. Mars, on the other hand, is just over half the diameter of Earth.