Our Night Sky: August 2021

It’s now August and a few weeks since the Summer Solstice, so you should be noticing it getting dark earlier at night. Because the Summer Triangle is still in the sky, you can continue to use it to find your way around the constellations. There’s lots to see with the cloudy core of the Milky Way being visible for about three hours after sunset and meteor showers returning with the peak of the Perseids on 12-13 August. The planets are also making a good show with Jupiter and Saturn being at their closest approach to Earth this year and this month.

Even under the light of an almost full moon, it was possible to see meteors as they flashed across the sky above Loch Sunart at Resipole during the August 2017 Perseid Meteor Shower

The Constellations

With sunset now at around 9:00 pm, the stars and the constellations will become visible from about 10:00 pm onwards. As with July, the best way to navigate your way around the night sky is to still use the Summer Triangle. The Triangle is made up of the three bright stars of Vega, Altair and Deneb. Start off by finding Vega, a really bright white star which will be directly overhead. Next is Altair, which you will find halfway between Vega and the southern horizon. Finally, there is Deneb, which will be almost directly above Altair and across from Vega.

Once you have found the Summer Triangle, you can now start to look for some constellations. There’s Cygnus the Swan, which is also known as the Northern Cross. It is a large cross-shape with Deneb at the top, marking the tail of a swan which flies down the Milky Way with outstretched wings towards Sagittarius (the Archer) which is low down on the southern horizon. It’s not a particularly bright constellation, so you’ll need a good clear night and to be far away from any light pollution to see it. As you trace a line between these two constellations, you should be able to make out the Milky Way’s cloudy core, which will be visible up until about three hours after sunset. 

Sagittarius makes a teapot shape low down on the southern horizon. It is rich in star clusters and nebulae, some of which you can see with binoculars on a night when the southern horizon is really clear. Above the spout is the Lagoon Nebula, a giant interstellar cloud that’s visible to the naked eye. Near to it and visible with a telescope is the three-lobed Trifid Nebula, while above Sagittarius and in the Milky Way, you will find a bright patch of stars called the Sagittarius Star Cloud (M24). Above this, is the Omega Nebula, which is one of the brightest and most massive star-forming regions of our galaxy.

​Off to the right of Vega, you can still see the spring constellations of Hercules, Corona Borealis (the Northern Crown) and Boötes (the Herdsman) and you can also pick out the constellation of Lyra (the Lyre), of which Vega is its brightest star. Below Vega, you will see Lyra’s 4 other main stars, which all form a small parallelogram. 

The Constellation of Cygnus
Image Credit: Till Credner [CC Share Alike 3]

​Although most of what to see is in the southern night sky, there are a few notable things to see if you look north. In the north-west, you will find the familiar shape of The Plough and you can use its two right hand stars to point towards Polaris (the Pole Star or North Star), which is always in the same position in the sky.

Southern Night Sky - August 2021
Created using SkyPortal Mobile App

Northern Night Sky - August 2021
Created using SkyPortal Mobile App

To the right of Polaris, you’ll see the W-shape of Cassiopeia, the constellation that represents the fabled vain queen of the same name. At this time of year her husband, king Cepheus, is high in the sky, though his stars are nothing like as bright as those of his beautiful wife. Below Cassiopeia are the stars of Perseus, after which the Perseid meteors are named. These meteors will peak on the night of 12-13 August, and you can find out more about them below. Finally, low down and below Perseus is Capella, the brightest star in the constellation of Auriga (the Charioteer) and the sixth-brightest star in the night sky. ​

The Moon

​At the very start of the month, we just miss the last quarter Moon as it was on 31 July, while there is a new Moon (no Moon) on 8 August. So, if it’s clear on the evening of 9 August, you will find the slightest of crescent Moons setting in the west at around 9:00 pm with a bright Venus to its left. 

However, it will be difficult to see the moon on 9 August as it will be lying close to where the sun has set, so you'll probably find it easier to see it on the following evening, 10 August, as it will have moved slightly to the left and will be sitting further from the sun and closer to Venus. Try again on 11 August and you may see the moon lying to the left of Venus.

The first quarter Moon (a half moon) is on 15 August while the full moon is on the night of 21-22 August, when it will rise in the south-east at around 9:30pm, with Saturn above and to the right of it and Jupiter above and to the left of it. August’s full moon was called the Sturgeon Moon by North American fishing tribes because this species of fish appeared in large numbers during this month. It's also been called the green corn moon, the grain moon, and the red moon for the reddish hue it often takes on in the summer haze.

The Planets

​When it is getting dark, the first thing you spot will be Venus. It will be low down on the western horizon in the dusk twilight, just before it sets at around 9:30 pm. Mars will be close to it, but this planet will be difficult to see because it is almost 200 times fainter than the “Evening Star”.  
 
If looking for planets, you will have more success when looking to the south-east at dusk because two of our Solar System’s gas giants, Jupiter and Saturn will rise from there at about 9:00 pm and will be at their closest approach to Earth this year and this month. First there is Saturn, reaching ‘just’ 831 million miles away on 2 August, while Jupiter passes its closest to us on 20 August, at 373 million miles away.
 
Jupiter is the brighter of the two planets. It will be sitting to the left of Saturn and if you look at it through binoculars, you’ll see its four largest moons. They are Io, Europa, Ganymede, and Callisto and are known as the Galilean moons. With a telescope, you’ll also be able to see the dark belts of Jupiter crossing its disc, and maybe, if you are lucky, the storm known as the Great Red Spot.
 
If your binoculars or telescope magnify by about 40 or 50 times, you be able to see Saturn’s famous rings and its biggest moons when you look at it. The largest, Titan, is enormous. In fact, it’s 40% more massive than the planet Mercury and 80% more massive than our own moon.

Meteor Showers 

​After a few months’ absence, you’ll be able to see some shooting starts because the number of meteor showers is now on the increase. In fact, this August will be a great month for watching shooting stars because the annual Perseid Meteor Shower will peak on a night when the Moon is only a crescent and sets soon after the Sun. This is the night of 12-13 August and with no moon to drown out the shooting stars, you are likely to see them from the hour or so after sunset.
 
They are called Perseids because the radiant (the area of the sky where the meteors seem to originate) is located near the constellation of Perseus and although you’ll be able to see them throughout the night, you will see more if you wait until this radiant is high in the night sky. This will be from about midnight and if you watch until dawn, the shooting stars will be raining down from overhead.
 
When watching for shooting stars, give yourself at least an hour of observing time, because they will come in spurts, interspersed with lulls. Also remember that your eyes can take as long as 20 minutes to adapt to the darkness of night, so don’t rush the process. If you are patient, you may see up to 60 meteors per hour at the shower’s peak.