The summer Milky Way
Despite the shortage of night hours, the middle of our galaxy takes centre stage for a spellbinding sight during the warmer months
If you can observe from somewhere dark, then the summertime Milky Way is one of the most spectacular sights you will ever see in the night sky. The further south you go the better, because the brightest parts of the Milky Way are found in southern constellations such as Sagittarius (the Archer) and Scorpius (the Scorpion). If you are able to travel to locations such as Florida or the Canary Islands on holiday in summer and venture out to a dark site with no light pollution, you’ll be stunned at how bright the Milky Way appears. It will look like shimmering clouds rising up from the horizon.
The first thing that you’ll notice is that there is structure in the Milky Way: parts that are brighter, and some parts that are dark with barely any stars at all. These are called dark nebulae. They may look like holes in space, but they’re not – they are huge clouds of cold gas and dust, cocoons inside which baby stars are being nurtured.
The very centre of our galaxy is in the direction of Sagittarius. We can’t see it because the stars, dust and gas of the Milky Way in front of it block our view. As it climbs north, the Milky Way enters the Summer Triangle, an asterism made up of three bright stars – Deneb of Cygnus (the Swan), Altair in Aquila (the Eagle) and Vega in Lyra (the Harp) – which mark the corners of the distinctive triangle.
1 North America Nebula (NGC 7000)
Constellation: Cygnus
Right Ascension: 20h 59m 17s Declination: +44° 31’ 44” Magnitude: +4.0
Minimum optical aid: 10x50 binoculars or a four-inch telescope
Most objects in the night sky only look tenuously like the things they’re named after, but the North America Nebula is the spitting image of the continent – it even has a curved gap that resembles the Gulf of Mexico. In reality it is an emission nebula approximately 2,200 light years away that is forming stars. It is bright, but large and diffuse, so despite being magnitude +4.0 it is very difficult to see with the naked eye, and ideally you need to view it through an instrument with a field of view of at least three degrees to encompass it all: 10x50 binoculars or a four-inch scope should do the trick.
2 Messier 26
Constellation: Scutum
Right Ascension: 18h 45m 18s Declination: -9° 24’ 00” Magnitude: +8.0
Minimum optical aid: Six-inch telescope
This is an open cluster, which is a loose grouping of young stars that formed together. It is 5,003 light years away, but can be difficult to spot amid the crowded star fields of the Milky Way. In a telescope at high-power magnification, you will be able to resolve up to 25 stars. Look closely and you may also be able to make out the long lanes of dark nebulae around the cluster.
3 The Swan Nebula (Messier 17)
Constellation: Sagittarius
Right Ascension: 18h 20m 26s Declination: -16° 10’ 36” Magnitude: +6.0
Minimum optical aid: Four-inch refractor or five-inch reflector
Near Sagittarius’ border with the constellation of Scutum (the Shield) lies this emission nebula, which is another star-forming zone and one of the best in the sky, but because it is so low when seen from the UK, it loses some of its splendour. It’s sometimes called the Omega Nebula because in a modest telescope at low magnification it looks a bit like a ghostly Greek letter Omega.
4 Trifid Nebula (Messier 20)
Constellation: Sagittarius
Right Ascension: 18h 02m 23s Declination: -23° 01’ 48” Magnitude: +6.3
Minimum optical aid: Five-inch telescope
The Trifid Nebula was named by Sir John Herschel, son of William, who saw the nebula divided into three lobes by dark dust lanes – but there are actually four lobes. The Trifid is a mixture of three types of nebulae: an emission nebula (the redder areas), a reflection nebula (the blue regions) and dark nebulae that divide the lobes. Emission nebulae glow when heated by hot stars, while reflection nebulae reflect the light of bright stars.
5 Barnard 86 and NGC 6520
Constellation: Sagittarius
Right Ascension: 18h 03m 48s
Declination: -27° 53’ 00”
Magnitude: +9.0 (NGC 6520)
Minimum optical aid: Four-inch refractor or five-inch reflector
Barnard 86 is a classic example of a dark nebula, made of gas clouds filled with impenetrable black dust. It lies next to the open cluster NGC 6520 to the east. Try observing the pair together through your telescope using a magnification of 100x.
“The further south you go the better; the brightest parts of the Milky Way are in southern constellations”