The Milky Way, above Uluru in Australia
Stefan Liebermann/mauritius images GmbH/Alamy
Because I’m based in the northern hemisphere, my suggestions of what to look for in the skies can sometimes be skewed towards what we can see from that half of the planet. So, in this month’s column I’ll focus on a feature of our skies that is undoubtedly best when viewed from the southern hemisphere, and particularly at this time of year: the Milky Way.
Every star you can see with the naked eye belongs to our galaxy, which means whenever you see stars, you are seeing within the Milky Way. So when stargazers refer to the Milky Way, they mean the bulge teeming with stars and dust that sit towards the centre of the spiral galaxy. The plane of the Milky Way is offset from the plane of our solar system by about 60 degrees, giving us a side-on view of the inner edge of our spiral arm from where we sit. It looks like an arc when we see it in the sky because we are seeing it on a three-dimensional, curved “surface”.
That view is even better from the southern hemisphere, thanks to Earth’s tilt. Stargazers in the southern half of the planet are tilted towards the centre of the galaxy, whereas in the north, we are facing away from the galaxy’s middle, towards a comparable desert of stars. This means that from the south you can see more of the constellations around the centre of the galaxy, like Centaurus and Sagittarius.
Wherever you live in the world, Milky Way viewing is at its best this time of year because we are on the same side of the sun as it is. But down south, stargazers always see more of the Milky Way because of Earth’s tilt, as well as having the bonus of dark nights at the moment.
According to a decade-old study, a third of the world’s population cannot see the Milky Way. It seems likely that the number has only gone up since then, thanks to increased light pollution. I urge you to find a clear evening with little moonlight. Around 25 June will be perfect, when we’ll have a new moon. Get away from light pollution and allow at least 40 minutes for your eyes adjust to the dark. If you are in the northern hemisphere, you might have to wait until at least midnight for it to be dark enough.
Two of the most memorable stargazing nights of my life happened in the southern hemisphere. The first was at Mount Cook in New Zealand in early June; the second was in Warrumbungle National Park in Australia in April. Both times, I was absolutely blown away by the view of the Milky Way, pictured here above Uluru in Australia.
If you ever get to stargaze in the southern hemisphere, do look for the Milky Way. You might even get to see beyond it to two of our satellite galaxies – the Large Magellanic Cloud and the Small Magellanic Cloud. Neither is visible from the northern hemisphere, but can be spotted near the southern celestial pole.
Abigail Beall is a features editor at New Scientist and author of The Art of Urban Astronomy. Follow her @abbybeall
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