July is a month for late night owls. This year, patience and a cup or two of strong coffee can be rewarded by the sight of Jupiter and Saturn close to each other towards the south after midnight. They are not hard to find, especially given the brightness of Jupiter.
Use it to find Saturn to its left. Both planets are at “opposition” meaning they are at their closest approach to the Earth in 2020 and are fully illuminated by the Sun. Strictly speaking Jupiter is at opposition on 14th July and Saturn on 20th, but the actual dates make very little difference. The relative closeness of the two planets – Jupiter will be 620 million km away and Saturn 1.3 billion km – means they will look bigger in a pair of binoculars or small telescope than later in the year. So you can see more detail.
For Jupiter you should be able to observe up to four bright points of light which are its largest moons. Just like our own Moon these move as they orbit Jupiter, so their exact configuration will change from night to night and this can be fascinating to track. Indeed it was the observation by the Italian astronomer Galileo Galilei of repetitive movement of these four points of light that led him to conclude they were in orbit around Jupiter.
In its day this was a massive discovery which played a key role in challenging our understanding from one where we thought the Earth was at the centre of the Universe to one where we thought the Sun might take that pride of place.
Today, we know both models are incorrect and indeed there is no absolute agreement on how best to describe our Universe! This makes it a very exciting time for all of us as we strive to get a handle on our ultimate origins and our ultimate fate.
The defining feature of Saturn is, of course, its wonderful rings. They are formed from billions of icy particles, each with their individual orbit around the planet. They range in size from less than the width of a human hair to large boulders and everything in-between.
From a distance the rings might appear static, but up close they would be revealed to be a roaring sea of organised chaos punctuated by collisions as the particles and boulders are tossed about by the interplay of the gravity between Saturn and its moons.
The best way to observe Jupiter and Saturn is with a small telescope, but binoculars will reveal much also. If the skies are steady, for example after a good shower of rain, you will be able to see more detail. For example, the Great Red Spot on Jupiter is a huge storm big enough to cover the Earth entirely. It has been raging for hundreds of years. Along with this are bands of clouds with wind speeds ranging from 380 km/hr to over 700 km/hr. Yet just like the rings of Saturn, the scene from the Earth is one of apparent calm!
Turning our attention elsewhere in the sky in July, the Delta Aquarids meteor shower peaks on the night of 28th and morning of 29th July, with the brightest meteors appearing after midnight. Delta Aquarids are the result of debris from two comets, Marsden and Kracht, and while the shower is not normally spectacular it’s worth keeping in mind that meteor showers are unpredictable and this year could be anything from exceptional to a damp squib – the uncertainty adds to the enjoyment! The best way to observe meteors is with your unaided eyes, from as dark a location as possible.
And remember, put away your mobile phones as these destroy your night vision for up to 20 minutes. And if you’re worried about finding that warming cup of coffee in the dark, you’ll be surprised how much you can see when you let your eyes adapt. Truly remarkable – try it.