The beautiful ringed planet Saturn made its closest approach to Earth of the year. On August 14, Saturn is 8.86 AU from Earth. An astronomical unit is the radius of the Earth’s orbit around the sun. Equal to about 150m km, which places Saturn 1.3 billion km away at this time. Traveling at an average speed of 9.69 km per second, Saturn takes about 29.5 years to complete a single orbit around the sun. Moving almost three times as fast, Earth takes on Saturn every 378 days, passing directly between it and the sun. Seen from Earth, Saturn is in the center of the opposite side of the sky from the sun, so astronomers call this close pass “opposition.” As Earth approaches and slips past Saturn, our perspective makes the distant planet appear to temporarily recede against the starry background. For a few months, instead of its usual eastward movement through the constellations, the planet moves westward. This apparent “retrograde” movement began on June 4th and will last until October 23rd. The chart shows the view to the south at 0100 BST on 16 August. From Sydney, Australia, the planet appears due north at about midnight.
