A version of this piece was originally broadcast on Radio Scilly in August 2019.

We’ve had some delightful evenings stargazing in the last couple of weeks, with relatively cloudfree skies – and a late-rising Moon – meaning that between 9.30pm and 11.30pm (ish) there’s been a nice window for observing. By that I mean before the very bright Moon pops up and wipes out all but the brighter stars up there.
 
At this time of year the Milky Way arcs brightly across our sky. It’s something many visitors to Scilly come to marvel at and appreciate, thanks to our naturally dark skies here. It must be stressed that you need dark minimal light pollution to stand a chance of seeing it clearly, which wipes out much of the mainland! Indeed a recent report by the Campaign for Rural England warned that many children in the UK risk growing up never seeing the Milky Way, because of the damaging effect of artificial light on the night sky. Unless they live in rural areas, and that’s a real deprivation.
 
One sad fact is that England has only 21.7% of pristine, unpolluted sky left (even sadder is that most of these areas are sparsely or unpopulated – so go figure what the cause is).
 
Anyway, we treasure our dark sky here in Scilly and long may our nights gazing at the Milky Way continue. But what is the Milky Way and what are we seeing when we look at it?
 
The Milky Way is the galaxy that our Sun, and therefore our solar system, belongs to. In fact, all the individual stars we can see in our night sky are part of the same galaxy, the same Milky Way.
 
A galaxy is a group of stars, gas, dust, remains of stars, and dark matter, bound together by gravity. There are several different types of galaxy, named by shape. The Milky Way is a spiral galaxy, which means it resembles…a spiral. Following so far? Our Milky Way is somewhere between 150,000 and 200,000 light years across. So, very big then. You might at this stage be wondering how on earth we know all this. And the answer is, very clever guess work, scientific estimations – based on other spiral galaxies in space and observations of patterns of behaviour of the stars we can see. If you’re still doubting, you’ll have to take my word for it.
 
We are inside the galaxy, and as such we’ll never be able to see ALL of the stars in it. What we can see is a disk of stars that forms the Milky Way from inside the disk, which tells us that our galaxy is basically flat… but not much more.
 
Several telescopes have taken detailed images of the bar of the Milky Way, from different directions, and all have found a concentration of stars in a band in the middle, which adds evidence that we’re a spiral galaxy. Put it this way, if we were an elliptical galaxy, we’d see stars of our galaxy spread around the sky, not just in a single band.
 
At the centre of our galaxy is a dense bar-shaped cluster of stars, a veritable bulge, where most of the activity happens. And all the stars in our galaxy revolve around this galactic centre. It takes our Sun about 250 million years to do one full orbit so in terms of whether we notice the difference in our position, I’d say the answer is no.
 
Even though all the stars we can see in the sky are part of the Milky Way, the galaxy gets its name – no, not from the chocolate bar, the stars came first – but from how it appears as a milky band of light in the sky. So what are we looking at?
 
In short, that bright, milky streak in the sky, is what I’ve talked about: the bright, star-packed centre of our galaxy. Are we alone in it? Who knows. Give it a wave next time we get a clear night, and most of all appreciate how lucky we are to be able to see this wonder at all.

A version of this piece was originally broadcast on Radio Scilly in August 2019.

We’ve had lots of lovely visitors to our observatory over the last couple of weeks, and thankfully the skies are getting just that little bit darker, so that now by 10pm you’ve got a good selection of stars and planets to ogle at. This week we enjoyed a great session looking at the first-quarter Moon through our two biggest telescopes and spotting Jupiter and Saturn along the ecliptic.
 
Remember that it’s the busiest time of year here on Scilly and our sessions have proven to be very popular, so we do recommend you booking in advance, particularly for evenings, if you’d like to visit us in person.
 
The star event this week is not a star but the Perseids. The annual Perseid meteor shower reaches its peak on the night of the 12th August this year. If the weather plays fair with us, you should be able to see up to 70 shooting stars per hour, streaking across our skies. However we will be subject to a bright Moon causing us some light pollution, which will drown out the fainter ones. Don’t let this put you off though – the Perseid meteor shower is one of the best and most loved meteor showers in the northern hemisphere, for good reason. These meteors can be spectacular.
 
You don’t have to wait until Monday night to spot Perseids. We tend to focus on the peak of activity, entirely reasonable, but actually Perseids have been streaking across our sky since about the 17th July, and activity has ramped up from the beginning of August. You might have even seen some already! The Perseids tend to take a while to build up to a peak before falling off sharply – though we’ll still see them up to 10 days after the peak of activity on the 12th.

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 So what do they look like and why are they so special?
Perseid meteors are particularly bright and fast with lovely long trails. It’s one of the most active meteor showers of the whole year. There’s a particularly high chance of seeing fireballs – very bright meteors – as well. While they can be seen streaking across any part of the sky, they seem to radiate – or come from – within the constellation of Perseus, or, to my mind and somewhat easier to spot, below the wonky W of Cassiopeia.
 
Meteors in these annual showers come from streams of debris left behind in space, by comets. In this case, that’s Comet Swift Tuttle. As our planet Earth crosses the orbital path of Comet Swift Tuttle, bits of the comet’s debris slam into our Earth’s upper atmosphere at an average speed of 36 miles per second, burning up on impact. This force of energy causes quite the night-time light show from these fast-moving meteors.
 
And how best to view the Perseids?
The good news is that you don’t need any special equipment or knowledge of the constellations! Get yourself to a spot where you’ve got dark, open sky. Open sky is essential because these meteors fly across the sky in many directions and in front of lots of different constellations. On Scilly, finding dark and open sky is an easy one, but you’ll still want to take yourself away from any outdoor lighting or glare from house lights. You might want to lie on the grass - or beach - or get yourself a nice reclining deck chair with a blanket!
 
The weather for the peak of the activity this year is looking variable, though we may be lucky enough to snatch some cloud-free moments. The best time to look is towards midnight and after, when the chances of seeing increase. However, meteors are part of nature and there’s no way to predict how many you’ll see during any given period. Be patient. In any case, to get the best of it, give yourself at least an hour of observing time – and remember your eyes can take up to 20 minutes to adjust to the dark. Perseids can come in fits and starts and good things come to those who wait. Find yourself a good spot and relax – you’ll see some.
 
Let us know how you get on – and remember you can share any photos on our COSMOS Facebook group or email them to me at [email protected]. Enjoy those shooting stars!