The Night Sky

by Chris Lawton

The Constellations

Looking up at the clear night sky there appears at first to be nothing but a random mass of dots. With a little experience these dots adopt patterns with individual characteristics and names. Perhaps the most famous of all constellations is Orion the Hunter locked into a heavenly battle against Taurus the Bull. Ursa Major and Minor point the way northwards whilst Cygnus, Aquilla and Lyra form the summer triangle.

There are in fact 88 constellations in total as defined by the International Astronomical Union (IAU) in 1922. Prior to this it was a general free for all approach - you could define what you wanted how you wanted. In AD 150 Ptolemy published a list of 48 some of which are still used today. The largest of all the constellations is Hydra, the water snake. It is 19 times larger than the smallest Crux, the southern cross.

If you click here then you can go direct to one of the pages supplied by Astronomy Now. This page lists some of the objects currently observable from Britain and the times to witness certain events. Astronomy Now is the only UK based astronomy magazine. It provides vital information to the amateur astronomical community.

The Planets

To the naked eye the planets are not particularly interesting. Knowledge of their position is, however, useful to know. The easiest to find are Jupiter and Venus due to their brightness. Mercury can be found but it is very difficult due to its proximity to the sun. Mars and Saturn are the only other two planets visible to the naked eye. A small pair of binoculars will reveal the Galilean moons of Jupiter and possibly show evidence for the rings of Saturn as a bulge in one direction. Uranus is technically visible to the naked eye but is very faint.

Neptune and Pluto require a telescope and no details will be seen. More details on all the planets are given in the The Planets section.

The Moon

The moon, when full, dominates the night sky. Because of its proximity features can be picked out even with low power devices. One feature to concentrate on is the terminator - the point where day night meet. More details on the moon and man's visits can be found in the moon section.

The Stars

Stars are generally uninteresting objects to view but there are, as always, exceptions. Many of the stars are in binary systems and telescopes often reveal fainter companion stars. One to look for is in Ursa Major. There are seven key defining stars known as the plough or big dipper. The handle of the dipper contains three stars in an arc. The middle star, also the uppermost, is known as Mizar. It has a companion Alcor which can be split by eye under good conditions. More detailed viewing will show a third star also in the same system.

Stars also appear in clusters. There are two types - open and globular. Open clusters contain very young stars. The most famous are the Pleiades - or seven sisters. It is found in the constellation of Taurus and to the naked eye appears as six or seven fuzzy stars. Again detailed observations show more than these seven bright stars but in fact there are some two hundred stars. Also in Taurus is the Hyades cluster. This cluster is centered around Alderbaran the brightest star in the constellation. It should be noted that Aldebaran is not part of the cluster but is actually closer to us.

Globular clusters are much older, more compact, objects existing on the edges of our galaxy. There are three fine examples - w Centauri, 47 Tucanae and M13. The first two are the finest examples but are, unfortunately, not viewable from Britain. M13 is to be found in the constellation of Hercules. To the unaided eye it can be seen as a fuzzy patch. Under a telescope it explodes into a body containing thousands of stars. These are believed to be some of the oldest objects in the universe.

Nebulae

Nebulae are the birth place of stars and also form the remnants of long gone stars. The most famous nebula in Orion. M42 is a vast birth place for stars and is a much studied object. The nebula can be discerned by the naked eye as a mist just below the sword of Orion. In a telescope and binoculars the true complexity of the nebula can be seen. Also in Orion is the Horsehead Nebula. A definitive black horsehead is seen by dust sitting in front of the nebulous gas behind it. Images of it are some of the most beautiful in astronomy.

Galaxies

Only one galaxy can be seen to the naked eye in the northern hemisphere. It is found in the constellation of Andromeda and represents one of our closest galactic neighbours. It appears as a large fuzzy blob and under binoculars the image doesn't really change all that much. With a telescope even of small size many other galaxies can be seen. The best examples are the Whirlpool Galaxy in M51, M81 in Ursa Major and NGC5128 in Centaurus.

Other Events

Finally the unexpected. Go out star gazing for any period of time and you will probably see at least one meteor cross the sky in an evening. These sporadic meteors are caused by dust and rocks burning up in the upper atmosphere as they are captured by the earth. A few times a year there are "displays" of these events. The best events to watch are the Perseids in August, Orionids in October, Geminids in December and the Quadrantids in January.

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