Sky Matters - Take the opportunity to look for the summer Milky Way

Although the summer nights are gradually getting longer, they remain short in July and even away from city lights there is a faint glow in the night sky, writes Niall Smith.

At this time of year the sun never dips very far below the horizon and so particles high up in the Earth’s atmosphere scatter some of light down towards the ground. Similar particles are responsible for the blue colour of our daytime sky. By contrast, the sky on Mars in a Martian day is a salmon-pink colour.

This is because the particles in the atmosphere are smaller than their Earthly counterparts and they scatter red light more than blue light. The particles themselves get high up into the Martian atmosphere thanks to dust storms which can sometimes grow to cover almost the entire planet. Martian particles are composed largely of iron oxide which covers the surface of the planet giving it its characteristic red colour.

The rust on Mars is evidence that the planet was much wetter in the past. After all, the easiest way to make lots of rust is to allow iron and water to interact, and that has fuelled speculation about the possibility of life on what was once considered a barren world devoid of any life-support system. Not surprising then that Mars is the most studied planet beyond our own.

You can still see Mars by turning your gaze due south after dark. It’s hard to miss its red colour. To the “upper left” of Mars is Saturn, somewhat unremarkable at present because of its distance from the Earth. On July 16, the moon, Saturn and Mars are in a straight line, in that order, and if you’re unsure of how to find Saturn then this should help you. Of course if you have even a small telescope, Saturn’s rings are a dead giveaway. If you imagine a line from Saturn to Mars and up to your right across the sky you will come to the planet Jupiter, the largest in the Solar System. Like all planets, you can only see Jupiter because it reflects the light from the Sun.

On July 4, Nasa’s Juno spacecraft will arrive at Jupiter after a five-year journey which has seen the spacecraft plunged into the freezing depths of space, and at the same time bombarded by high-energy particles ejected by both our own sun and bizarre objects like exploding stars or colliding black holes, or all manners of exotic objects out in distant space.

Juno will orbit Jupiter from pole-to-pole and help us understand how this majestic planet evolved. July 4 is also auspicious as the date when the Earth is farthest from the sun.

The Delta Aquarids meteor shower peaks on July 28 and 29. This is a moderate shower with about 20 meteors, or shooting stars, per hour. Look generally east, but be aware that Delta Aquarids can appear anywhere in the sky. The best time to observe them is after midnight. The quarter moon will not generally interfere, rising about 2am on July 29.

Take the opportunity to look for the summer Milky Way appearing as a faint band of light that starts around Mars, passes pretty much overhead, working its way through the Summer Triangle stars of Altair, Vega and Deneb and ending up almost due north at the horizon where Capella, the brightest star in the constellation Auriga and sixth brightest star in the sky, can be found in July. 


The sunsets and sunrises on Mars are blue, not red like our own. A case perhaps of “Blue skies at night, Martian shepherds delight”?


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