Perseid nights
August’s peak of the Perseid meteor shower is likely to be affected by the Moon this year, so Stuart Atkinson selects some other targets to look out for
Enjoy the peak of this year’s Perseid meteor shower and take a tour of the night sky in August
There’s something of an annual stargazing ritual. In the same way that many of us go through the Christmas Radio Times, circling the films and TV specials we want to watch, at the start of every year amateur astronomers check the observing prospects for eclipses, comets and the planets during the months to follow. They also want to know how the major meteor showers will be affected by the Moon, especially the best shower of the year, the Perseids, which peaks in mid-August.
Guides to 2020 advised us that this would be a challenging year for Perseid watchers, when a last quarter Moon will be close to the shower radiant over the peak period. This means that fainter Perseids won’t be seen, and we’ll have to wait longer between meteors that are bright enough to see. It doesn’t have to be a bad thing however, as it means there’ll be plenty of time to enjoy observing other things.
Although the Moon will affect this year’s Perseid meteor shower, that doesn’t mean you should just forget about it and stay in bed. There will still be more shooting stars than usual skipping across the sky,
some of them very bright and colourful, and some could leave ghostly glowing trails behind them too. The Perseid peak is on 12 August, but estimated to be between 14:00–17:00 BST (13:00–16:00 UT). This means heightened activity will be on the night of 11/12 August (the rise to the peak) and 12/13 August (the fall from the peak).
You’ll be able to see some Perseids from your garden on the night of the 12 August, but to enjoy the shower at its best you’ll need to find a more favourable observing location, somewhere not affected by light pollution. It’s a good idea to scout about in advance for such a location, so you’re not driving about on the night.
Before heading out to watch the Perseids, make sure you’re dressed for a long night – with a warm jacket, gloves, hat and scarf – and have a hot drink and snacks to sustain you. If you don’t have any other meteor watchers for company, take a radio to keep you awake. Don’t sit on a wall, you’ll feel cold and damp creeping through you in no time; a deck chair or reclining chair will be much more comfortable. Be at your site by 22:30 BST (21:30 UT) and allow your eyes time to adapt to the darkness. Once you’ve achieved dark adaptation, don’t look right at Perseus; you’ll see more meteors if you look away from the radiant, off to either side of it or above it instead. Then… look up and wait.
How many meteors can you expect to see? Well, theoretically, one every minute or so, but realistically you’ll spot one perhaps every five minutes. Some will be very bright, others just glimpsed out of the corner of your eye. Don’t expect a steady stream of shooting stars; there’ll be long periods when you see none, followed by exciting flurries of activity. The trick is to just settle down and wait. And when you start yawning and that voice starts whispering in your ear, “Go home… the best is over… you need to sleep…” don’t give in. Stay out as long as you possibly can, because activity will be at its greatest in the hours before dawn.
While waiting for Perseids it’s the ideal time to enjoy looking at other things in the sky – and this year there will be a lot of fascinating ones to see. Here are some suggestions for other targets to search out, in between shooting stars.
A parade of planets
If your Perseid observing site has a flat, low horizon from the northeast to the south, you’ll be able to enjoy looking at a planetary parade while you wait for meteors to skim across the sky. On the evening of 12 August the show starts with Mars rising in the east around 22:45 BST (21:45 UT). Shining
impressively at around mag. –1.3 it will be very obvious to the naked eye, looking like a bright orange spark. Binoculars will enhance both its brightness and its glorious colour, and a telescope will show you its ochre disc, perhaps even its bright, icy south pole and dark features on its surface. It will dominate the evening sky in a couple of months.
Having found Mars, turn right until you are facing south, where you’ll see what look like two bright stars in the sky. These stars are actually two more planets. The brighter of the two will be Jupiter, with fainter Saturn just to its left. Binoculars won’t show you Saturn’s famous rings but you might make out its largest moon, Mercury-sized Titan, as a tiny star close on its right. Binoculars can also show you Jupiter’s four largest moons and, if you have a telescope with you, Jupiter’s yellow-white disc, crossed by bands of toffee-hued cloud, will be a lovely distraction during lulls in meteor activity.
Planets spotted, what else can you look at during the quiet periods of the meteor shower? How about a trip along the Milky Way? To begin, look towards the northeast where you’ll see a bright, yellow-white star twinkling away down near the horizon; this is Capella. A giant star, Capella is almost 43 lightyears away and is the closest first magnitude star to the celestial north pole: at mag. +0.08 it’s the sixth brightest star in the sky.
To Capella’s upper right you’ll see a pattern of stars that might remind you of a wishbone from a cooked chicken or even a pair of garden shears. This is the constellation of Perseus. The Perseid meteor shower is named after this constellation because its shooting stars appear to zip away from it during peak activity. You might recognise heroic Perseus from fantasy films, hacking the serpent-haired head off Medusa and riding his winged horse, Pegasus, across the sky.
Double beauty
Directly above Perseus you’ll see a very distinctive pattern of five stars in the shape of a W. We’ll come back to that. For now look roughly halfway between that W and Perseus: you’re looking for a misty smudge, more obvious if you look slightly to one side of it. This is a famous deep-sky object called the Double Cluster, a pair of beautiful, glittering star clusters, each containing thousands of stars. Although they appear to be side by side, the clusters are hundreds of lightyears apart.
Back to that W of stars. This is the constellation of Cassiopeia – representing a vain queen who was tossed into the heavens by the Greek gods for foolishly declaring she was more beautiful than any of them – and it can guide you to one of the best-loved deep-sky objects of all. If you split the W into two Vs the highest one points like an arrowhead to a small smudge. This is M31, the Andromeda Galaxy, a spiral galaxy around 2.5 million lightyears away that’s roughly twice the size of our Milky Way. It’s the most distant object the naked eye can see. Under a dark sky a pair of binoculars transforms that smudge into a misty oval, glowing with the combined light of a trillion distant suns.
Next, look almost overhead for what looks like a long, oval-shaped cloud there, almost as if someone has smudged chalk dust on the sky with their fingertip. This is the Cygnus Star Cloud, a region in the Milky Way so densely packed with stars that it looks like a cloud of smoke to the naked eye, but is resolved into countless stars through binoculars.
To the southeast of the Cygnus Star Cloud is a dark area, which looks as if someone has plucked all the stars out of the Milky Way. This is the Cygnus Dark Rift and it appears dark because clouds of dense interstellar dust are blocking our view of the stars in that direction.
Spotting the Summer Triangle
Neatly framing that bright star cloud and the dark rift running down along its side is a triangle of three bright stars. Deneb, Altair and Vega are known collectively as the Summer Triangle and are three of the brightest stars in the sky, shining at mag. +1.3, mag. +0.93 and mag. 0.0 respectively. Altair and Vega are both less than 30 lightyears distant, but Deneb is an incredible 2,600 lightyears away. About 200,000 times more luminous than our own Sun, Deneb is a true giant of a star and was the Pole Star 18,000 years ago. Due to the precession or wobbling of Earth’s axis it will be an approximate Pole Star again around the year 9800 AD.
Although the Summer Triangle is very distinctive, it’s not equilateral. If you look to Vega’s lower right you’ll see another star, Rasalhague, which is only second magnitude and this can be connected with Vega and Altair to form an equilateral triangle shape.
Below Rasalhague, down towards the horizon the Milky Way grows thicker and more clotted behind a pattern of stars that looks like a teapot or even a genie’s lamp. This is part of the constellation of Sagittarius, and it is crowded with fascinating deep-sky objects. Unfortunately, this part of the Milky Way never climbs very high in the northern sky, but if you sweep it with
binoculars you’ll see a subtle brightening if under dark skies. It’s a region that contains nebulae, glittering star clusters and simply too many background stars to count. This is the location of famous deep-sky objects such as the Omega Nebula, M17, the Lagoon Nebula, M8, the Trifid Nebula, M20 and the Wild Duck Cluster, M11. Use our chart (above) to find them – and imagine how stunning they would look from the Southern Hemisphere, where they’d be much higher in the sky.
Our fascinating tour concluded, turn your gaze east and you’ll see the sky brightening in that direction in advance of the Moon rising – at 23.50 BST (22:50 UT) on the night of the 11/12 August and 00:10 BST (23:10 UT) on the night after. There’s lots to see on the Moon through binoculars, but on these nights the brilliance of its last quarter phase will ruin your dark adaptation. For now, just be content to stand there in the dark and wait for shooting stars to start skipping across the sky. Even with the Moon there you’ll be in for a treat – and almost certainly a few jaw-dropping moments too.
► For more on the Perseids see pages 42, 64 and 68