This piece was originally broadcast on Radio Scilly in June 2019.
Hello from the Observatory on St Martin’s. I’ve been wowed by the Moon rising a glorious shade of orange this week – it’s rising late at the moment, just before and now just after midnight. If you’ve been awake to catch it, you might well be awestruck – as I was – by its vivid orange colour. This isn’t what we call a blood moon, but a result of the Earth’s atmosphere. The colour occurs when the Moon is low in the horizon, because you’re looking at it through more of the Earth’s atmosphere.
That atmosphere is filled with particles that absorb and scatter light. In short, the longer the lightwaves, the redder they appear. So when the light from the Moon travels through more atmosphere, the Moon appears redder in the sky. It’s the same reason – in principle – why sunsets appear red and orange.
To other glowing wonders in the sky. You can’t miss glorious Jupiter at the moment, fairly low in the Southern sky. It might be hard to spot in a built up city but not here on Scilly with our long, low horizons. You’ll be able to see it with the naked eye anytime from 10 o’clock – even when the sky isn’t fully dark. At magnitude -2.5 or thereabouts it’s the brightest thing in the sky after the sun sets. And well after that.
When you look at it with the naked eye, or at least when I do, it seems a little orangey and very bright! Remember it’s much, much closer to us than any of the stars we can see, so its light isn’t having to travel so far. And that’s even light reflected by the Sun – Jupiter doesn’t emit any of its own.
A telescope even of modest proportions will show the planet as a flattened disc, and you’ll be able to see two of its darker bands of clouds. The Southern band of cloud is home to the famous Great Red Spot. Bear in mind that you might not see it as Jupiter’s always on the move – spinning once on its axis every 9.8 hours.
Jupiter’s the undisputed king of the planets. It’s a whopper, weighing in at 318 times the mass of the Earth. It also has some 60 moons, compared to our 1. Its sheer mass and gravitational pull are also thought to have helped bring the planets into the positions we see today. Mentally it can be quite hard to visualise the sheer scale of our solar system. So I’ll very scientifically use St Martin’s single road to help us out.
Imagine this: If the Sun was the size of a beach ball, balanced on the end of Higher Town Quay, the Earth would be the size of a pea, roughly at the top of the quay. Walking on, we’ll pass Mars (outside Higher Town waiting room, and the size of a peppercorn). We’ll then keep walking up until we reach the top of Par Hill as the road turns a corner – and there we’ll find Jupiter, the size of an orange. (If you’re interested in going further, Saturn’s outside St Martin’s stores, the size of a lime…. But I’ll stop there)
However you do it, or choose to understand it, enjoy gazing at Jupiter – it’s currently at its best viewing all year. Now… to fix those clouds…