Star trek: the wonders of the night sky
Do yourself a favour and wrap up, go outside and take a closer look at the celestial wonders of the winter sky
A nebula in the constellation Orion, photographed in 1999. Photograph courtesy of Nasa
As I write this column, the incessant rain is wreaking havoc across the country and depressing the overall mood of the entire population. While I recognise the seriousness of the consequences of flooding and wind damage for many people, another, more trivial outcome that irritates me is the chronic obliteration of the night sky at a time when the winter constellations shine in all their glory, unseen above the cloud banks.
On January 27th, the International Dark Sky Association presented its Gold Standard award to the Kerry Dark Sky Reserve, a 700sq km area of the Iveragh Peninsula. The views of the sky there on a clear night must be truly spectacular. However, most of us can locate relatively dark areas of sky close to where we live. When the skies eventually clear, it will pay an enormous psychological dividend to wrap up, go outside and take a closer look at what’s been missing.
Perhaps the most obvious of the winter constellations is Orion, located at present in the southwestern sky. It forms a large rectangle of four bright stars, with a diagonal three-star “belt” at its centre, and a fuzzy luminosity below the belt, which is the great Orion nebula. Orion is depicted in Greek mythology as the hunter, with the four stars of the rectangle forming his body, the three centre stars his belt, and the nebula his sword.
The Orion nebula consists of clouds of dust and gas, young stars and stars in the process of formation. The Hubble Space Telescope has revealed protoplanetary discs in this region also, which indicate an early stage of solar system evolution. The nebula is an impressive sight through a pair of binoculars. It lies at a distance of approximately 1,350 light years, a light year being the distance light travels in one year as it travels at 186,000 miles per second.
The constellations are, in fact, visual illusions, created by our tendency to construct patterns from disparate information. When we view Orion against the blackness of space it appears to be
two-dimensional, and it seems as if the constituent stars are closely related. This is not the case. They are separated by vast distances in three dimensions.
As you view the constellation, the star at the top left is Betelgeuse, which lies at a distance of 640 light years. At the top right is Bellatrix at a distance of 250 light years; Rigel is at the bottom right, 850 light years away; while Saiph, at the bottom left, is 900 light years away. The three stars in the belt lie between 800 and 1,340 light years away.
It is obvious from this that astrological statements such as “Saturn moves through Aquarius” are meaningless. Constellations are psychological constructions, not actual entities. In a million years’ time, the constellations will look radically different due to relative motion of the stars.
Astronomy has become a very popular pastime, as indicated by the growing popularity of Astronomy Ireland (astronomy.ie). It was set up in 1990 by David Moore, and now has more than 1,300 members and engages in a wide range of activities around promoting astronomy.
This increasing interest is likely fuelled by some of the immense achievements of major astronomical instruments such as the Hubble Telescope, which has given us a plethora of wonderful images of deep space objects; the Very Large Telescope in Chile, which detected the first planet in orbit around another star; and the European Extremely Large Telescope, which will be constructed in the near future and will open up even wider horizons.
The recent achievement of the successful wake-up call to the comet-chasing spacecraft Rosetta will have captured the imaginations of more nascent astronomy buffs. The task assigned to this craft also indicates the precision of prediction inherent in science. Launched almost a decade ago, Rosetta will jettison a landing craft on to the surface of comet 67P/Churyumov-Gerasimenko, which is more than 500 million miles from Earth and has a nucleus that measures 5km by 3km. This is due to take place in November.
The wonders of the night sky are many, and they are easily and cheaply accessible. A basic guide to the night sky, such as Philip’s Stargazing 2014 , will get you started. It contains excellent sky maps, highlights the locations of the planets, and special astronomical events for each month, and discusses a particular object of interest. This month’s object is the star Rigel in Orion.
I think I see a break in the clouds.
Paul O’Donoghue, Irish Skeptics Society, email@example.com