Nebulae

The Summer Triangle

During the early evenings of September the Summer Triangle lies high in the south. In October it is to the south-west and by November it is in the west. To find it first look for the brightest star in the sky. That is Vega in the constellation of Lyra. Next look to it’s left to find Deneb in Cygnus. Finally look below Deneb to find Altair in the constellation of Aquila. These three stars form the summer triangle.

Aquila – The Eagle

Altair is the brightest star in the constellation of Aquila. In Greek mythology, Aquila was the eagle that carried Zeus’ thunderbolts.

Barnard’s “E”

On a clear moonless night look just above and to the right of Altair in Aquila using binoculars. You should be able to spot a mysterious dark “E” silhouetted against the faint background glow of the Milky Way.

This strange shape is a dark nebula; a cold cloud of interstellar gas and dust, so dense that it obscures the light from the stars behind it. These dark nebulae are where new stars will eventually be born.

Barnard’s “E” is named after Edward Barnard (1857 – 1923), a Victorian astronomer who compiled a list of dark markings in the sky.

The Arrow and the Fox

The constellation of Sagitta (the Arrow) can be found just above Aquila. Although small, it was recognised as an arrow by several ancient civilisations including the Persians, Hebrews, Greeks and Romans.

Vulpecula (The Fox) lies just above Sagitta. Unlike many other constellations it has no mythology associated with it. Vulpecula was introduced by the Polish astronomer Johannes Hevelius during the late 17^th century.

The Coathanger (Brocchi’s Cluster)

The eye and brain are excellent at seeing meaningful patterns in random collections of stars. Asterisms are obvious groupings of stars that are not one of the traditional constellations

The Coathanger is an unmistakable asterism despite being upside down! Find it about one binocular field to the north west of the western end of Sagitta. Although it’s stars appear to be close together, they are a chance alignment at very different distances from us.

The Dumbbell Nebula

A short distance to the east lies the Dumbbell Nebula. It is the biggest and brightest planetary nebula in the northern sky. Find it about half a binocular field north of the eastern end of Sagitta. It looks like a small faint planet just below the central star of a distinctive “M” shaped asterism.

A planetary nebula consists of an expanding shell of gas ejected from an old red giant star late in it’s life. They are relatively short- lived, lasting only a few tens of thousands of years, compared to a typical stellar lifetime of several billion years. They are called planetary nebulae because William Herschel thought that they resembled planets when viewed through his telescope in the 1780’s. The name has stuck although it is misleading.

Images by Jon Marcus and Petr Novak are licensed under a Creative Commons Attribution 4.0 International License.

Orion is one of the most recognizable constellations in the winter sky.

The easiest way to find Orion is to go outside in the evening this winter and look to the south east. You are looking for three bright stars close together in almost a straight line. These three stars represent Orion’s belt. The two bright stars to the north are his shoulders and the two to the south are his feet.

Orion the Hunter could walk on water because he was the son of the sea-god Poseidon. After many adventures Orion walked to the island of Crete where he hunted with the goddess Artemis. During the hunt, he threatened to kill every beast on Earth. But Mother Earth objected and sent a giant scorpion to kill him. After Orion’s death, Zeus placed him among the constellations adding the Scorpion as well, to commemorate the hero’s death.

One of the show pieces of Orion is the Great Nebula. To find it first locate Orion’s Belt, which contains the row of three bright stars. Next, look below his belt for a vertical row of fainter stars marking the Hunter’s Sword. Look for the fuzzy “star” in the middle of the Sword. That’s the Orion Nebula. Binoculars will give you a better view.

The Orion Nebula is a stellar nursery where new stars are being born. Stars form when clumps of hydrogen and other gases contract under their own gravity. As the gas collapses, the central clump grows stronger and the gas heats to extreme temperatures. When the temperature gets high enough, nuclear fusion ignites the gas to form a star. The star is ‘born’ when it begins to emit enough radiative energy to halt it’s gravitational collapse. Detailed observations have revealed approximately 700 stars in various stages of formation within this nebula.

The Pleiades – The Seven Sisters

Start by looking for the three stars in a diagonal row that make up Orion’s belt. Draw an imaginary line between those stars up and to the right. Continue your line, and you should come to a group of stars that looks like the letter “V”. That is the face of Taurus – The Bull. A little to the right of Taurus is a small clump of stars. They are the Pleiades, looking almost like a tiny dipper. Once again binoculars will give you a better view.

The Pleiades were the seven daughters of Atlas and the sea-nymph Pleione. After Atlas was forced to carry the heavens on his shoulders, Orion began to pursue all of the Pleiades. To comfort their father, Zeus transformed them first into doves, and then into stars. The constellation of Orion is said to still pursue The Pleiades across the night sky.

The Pleiades is an open star cluster containing hot middle-aged stars. It is one of the nearest star clusters to Earth. Probably formed from a nebula similar to the Orion Nebula around 100 million years ago, the cluster is dominated by hot blue and extremely luminous stars.

The faint reflection nebulosity around the brightest stars was at first thought to be left over from the formation of the cluster, but is now known to be an unrelated dust cloud in interstellar space, through which the stars are currently passing. Astronomers estimate that the cluster will survive for about another 250 million years, after which it’s stars will disperse.

Getting the best view

Discovering a dark place shouldn’t be too difficult on the Glenlivet Estate. I find my garden is as good a place as any. Switch off any outdoor lights and allow your eyes to acclimatise to the dark. In the dark your sensitive night time black and white vision will allow to you see more in the night sky, but it does take a while to kick in.

Avoid looking directly at any visible lighting. That will destroy your night vision almost instantly and you will have to wait another ten minutes before your dark adapted eyes are beginning to work again.

Because you are using your night vision you will only be seeing in black and white so don’t expect to see the Orion Nebula in full colour. Colour images can only be produced with long photographic exposures. Nevertheless witnessing the wonders of the night sky for yourself is an altogether different level of experience compared to admiring pictures by the Hubble space telescope from the comfort of your armchair.

Get out there and look up at our glorious dark skies!