The constellation Sagittarius, 1603.
© Science Museum / Science & Society Picture Library
Illustration taken from 'Uranometria' (1603) by Johann Bayer, showing the zodiacal constellation of Sagittarius (the Archer). German astronomer and lawyer Johann Bayer (1572-1625) invented the system for naming stars using letters from the Greek alphabet, a system still used today for the brighter stars - those visible to the human eye without the aid of a telescope. 'Uranometria' depicts the positions of nearly 1000 stars in addition to those identified by Tycho Brahe. Sagittarius contains more of the nebulae and star clusters catalogued by French astronomer Charles Mesier (1730-1817) than any other constellation. 30,000 light years distant from Earth in the direction of Sagittarius is the centre of our galaxy, detectable as a radio source.