Despite the onset of the much needed rainy season, the summer months in South Africa provide some absolute gems from an astronomical view. Admittedly the cloud cover can make this challenging but when clear skies are apparent, the next few months make for some impressive sights!
Here are my tips for what to look out for over the coming months
- The Square of Pegasus
The great square of Pegasus is one of the most recognizable constellations in the skies. As its name suggests, it is a massive square with the four corners highlighted by major stars. The area within the square is fairly devoid of other naked eye stars and thus should be simple to find above the northern horizon. Pegasus is named after the winged horse that, according to Greek mythology, sprang further from the neck of the Gorgon, Medusa, after she was beheaded by Perseus. The most famous myth involving Pegasus details its taming by Bellerophon in order to destroy the Chimaera, a fire breathing monster that was ravaging the lands.
- The Andromeda Galaxy (M31)
The Andromeda galaxy is our sister galaxy and can be located in the constellation of the same name. It is the furthest naked eye object visible in our skies and can be viewed as light smudge despite being around 2.5 million light years away! Similar in structure to our own Milky Way, Andromeda is far larger however and is home to an estimated 1 trillion stars! M31 is hurtling through space at around 100km/second and is expected to collide with the Milky Way in about 4 billion years… When this finally happens, it is expected that the 2 galaxies will merge into what has been dubbed ‘Milkdromeda’.
- Cygnus , The Swan
Cynus is a large cross-shaped constellation whose long axis follows the line of the Milky Way. It can be seen clearly in the northern skies and is marked by the bright star, Deneb, at its base. For amateur astronomers however, the most popular sight is Albireo, a double star located at the point of the cross. The 2 stars create a beautiful contrast in colours when viewed in a telescope with one member being brilliant yellow and the other a vivid blue. Due to its position in the Milky Way, Cygnus hosts a multitude of deep sky objects including NGC 7000, the North American Nebula.
- Delphinus, The Dolphin
Although one of the smallest constellations in the sky, Delphinus is one of the most recognizable as it is one of the few that actually resemble its namesake. The 5 main stars trace out the shape of a dolphin diving into the water and can be seen to the north of Pegasus. Delphinus is considered to be the messenger of Poseidon, the god of the seas.
- The Hyades
This open cluster is the closest of its kind to our solar system at a mere 150 light years away. It is found within the constellation of Taurus, the Bull, and represents the famous ‘V’ shape of the bull’s horns. It is easy to view even without binoculars and is marked by the orange giant, Aldebaran (although this famous star is not associated with the cluster itself.) Open clusters are groups of stars that are all related and thus borne from the same nebula. They are travelling through space together but will slowly disperse over the years as they are influenced by other celestial phenomena. Around 15 of its several hundred stars are visible with the naked eye and they are said to represent the daughters of Atlas.
- Orion, The Hunter
Without doubt, the most famous and recognizable constellation in the night sky is Orion. Orion is visible rising in the east and will soon dominate the night sky at peak viewing hours. There are various mythologies detailing the exploits of the great hunter, but all share one common theme and that is his relationship with the 2nd most well-known constellation, Scorpius. The 2 are located at opposites of the celestial sphere and thus Scorpius is sinking below the horizon in the west as Orion rises in the east. The most famous myth describes Orion as the great hunter whose arrogance caused him to kill with abandon. The gods were concerned by his skill and ruthlessness and thus sent a scorpion to confront him. The scorpion and Orion were both killed during the battle and honoured in the stars at opposites to one another. The effect of their location in the celestial sphere is that Orion is forever fleeing from his nemesis as they chase each other across the night sky.
This massive red supergiant star marks one of the shoulders of Orion and its colour is easily visible to the naked eye. Although named Alpha Orionis, Betelgeuse is fainter than Orion’s brightest star, Rigel. The Greek designations are usually assigned in order of magnitude and thus this label seems incorrect. However, due to is size and instability, Betelgeuse varies in brightness and when the stars were given their original designations, it may well have outshone Rigel. Red supergiants are nearing the end of their lives and Betelgeuse is expected to destroy itself in a supernova in the next few thousand years. When it does, the energy released will light up the skies, outshining the Moon and will even be visible during the day!
- The Orion Nebula (M42)
Despite the fact that M42 was discussed in the January to March edition of this series, it is impossible not to mention it again. The Orion Nebula is probably the most famous deep sky object in the sky and is clearly visible with the naked eye. Look for the line of stars that represent the sword of Orion and you will notice that the middle star is hazy. This is actually a massive area of dust and gas within which new stars are being born. Over 1000 recently formed stars reside there with another 700 or so in various stages of development. As the closest star forming region to Earth, the Orion Nebula has given astronomers a wealth of understanding of the origin of stars themselves.
Blog by Ben Coley