The Night Sky in August PETE LAWRENCE
At the start of 2022, the bright planets migrated into the morning sky and coupled with the decreasing length of night as moved towards this year’s summer, it meant they weren’t best place for viewing earlier in the year. Now however, this has started to change.
Saturn leads the way, shining against the stars of eastern Capricornus with an off-white hue. It is highest – roughly one-fifth the way up the sky, due south– around 1am BST mid-month and midnight BST on August 31.
Saturn reaches opposition on August 14, so-called because it marks a time when a planet or the Moon is opposite the Sun in the sky. For a planet it also marks a time when it is closest to Earth for the current period of observation, appearing brighter and larger through a telescope. The effect diminishes the further the planet is out from the Sun. For Mars opposition makes an enormous difference to its appearance. For Jupiter, less so and for the Ice Giants Uranus and Neptune, hardly any difference at all. Saturn however, is an exception thanks to its superb ring system.
Saturn’s rings are composed of a myriad of mostly water-ice particles ranging in size from millimetres to several metres. Each one casts a shadow that darkens the particles behind it. Seen from the side, the rings are subtly darkened by the visibility of these shadows. At opposition, the shadows line up behind the particles that cast them and become less pronounced. As a result, observing Saturn through a telescope in the week approaching opposition, the rings appear to brighten, reaching a peak on opposition day. After opposition, it takes about a week for the rings to dim back to normal brightness.
East of Saturn and higher in the sky, is the intensely bright dot of Jupiter. With roughly twice the peak altitude of Saturn when due south, Jupiter is in a much better place to view using a telescope as it’s higher position in the sky takes it out of the low level, turbulent atmospheric layer close to the horizon. A telescope will show the planet’s oblate disc, a consequence of its gaseous composition being subject to a rapid day rotation of less than 10 hours. A telescope also reveals atmospheric features such as dark bands and, with a 100mm or larger scope, the famous Great Red Spot. The four brightest moons, the so-called Galilean moons, are easily visible through any size of telescope and even binoculars if you can keep them steady.
Between Saturn and Jupiter lurks dim Neptune, the most distant main planet in the Solar System. It’s below naked eye visibility and requires at least binoculars to see.
Keep going from Saturn through Jupiter for roughly the same distance and you’ll arrive at orange-hued Mars. This planet is heading for opposition later in the year, so its appearance will improve dramatically over the coming months.
Uranus is near Mars at the start of August, the Red Planet rapidly moving east (left) during the rest of the month. Uranus is theoretically visible to the naked eye from a dark location, but binoculars are the best way to find it.
What of the inferior (closer to the Sun than Earth) planets, Mercury and Venus?
Mercury is badly placed in the evening sky and not easy to see after sunset. Venus is in the morning sky, creeping ever closer to the Sun. On August 26, if you can catch Venus low above the east-north-east horizon, say an hour before sunrise, look out for a very thin, 1pc-lit waning crescent Moon just left of the planet.