The Night Sky in July 2012 An artist's impression of what all the water in the world would look like if it was squeezed into a ball. But like all the rocky planets, Earth has a tremendously dense core making such life impossible, perhaps made of molten iron. This is not true of all the solar system's moons. Jupiter's moon Europa, with only a quarter of Earth's diameter, is a body made largely of ice with an underground ocean thought to be 100 miles deep. The constellation of Andromeda, the Chained Woman, is now well in view in the north-east, with its most famous object the great spiral galaxy M31 - the only other galaxy apart from our own that is visible with the naked eye. M31 is vital in our history. Edwin Hubble showed in 1923 that it had its own stars, thus making it a galaxy independent of ours. And this had to be true of the other mysterious "nebulae" that dotted the sky. They had also to be at unimaginable distances. He thus, at a stroke, made the universe hundreds of millions of times larger. Cassiopeia, the constellation supposedly named after a vain and boastful queen, lies north of Andromeda. It is a spectacular star-filled region because, unlike Andromeda, it runs though the Milky Way. Its five brightest stars make a W-shaped formation. Last year four Israeli war planes went up to investigate the supposed "enemy aircraft" that it mistook for these stars. In neighbouring Cepheus, the most interesting object is the Garnet Star, Mu Cephei, that shines like a glowing coal. This is one of the three largest known stars in the galaxy. If the Sun was the size of a golf ball, the Garnet Star would be as big as Greater London. It may explode as a supernova but at 6,000 light-years cannot harm us. It needs imagination to recognise the objects represented by the constellations. Some of their names may be more than 5,000 years old. Forty-eight of the 88 constellations are believed to be extremely ancient. There are no crocodiles or hippopotami among them that the ancient Egyptians would have introduced; nor even any elephants or tigers that the earliest Indian civilisation might have imagined. There are only animals like bears from legends of unknown antiquity. This preoccupation with animals may stem from the same impulse that led to the cave paintings at Lascaux tens of thousands of years earlier. Saturn and Mars can be seen up until midnight. Please send comments to adrianspage@safe-mail.net Adrian Berry's Book Eureka: The Book of Scientific Anecdotes can be downloaded from Kindle The new Daily Telegraph Night Sky Chart is available for £9.95 plus 99p p&p. To order, please call Telegraph Books on 0844 871 1514, or visit www.books.telegraph.co.uk, or send a cheque to Telegraph Books, Orders Dept, PO Box 582, Norwich NR7 0GB.