supposed linear features on Mars. The Italian word canale, meaning simply channel, was used in the nineteenth century by Angelo Secchi to describe linear features he perceived during observations of Mars, and later by Giovanni Schiaparelli. The word was translated into English as canal with the connotation that what had been observed were artificial structures. The notion was elaborated by Percival Lowell, who built an observatory at Flagstaff, Arizona, with the main purpose of observing Mars. His drawings of the planet showed extensive networks of linear canals, and he proposed that a civilization of intelligent beings on Mars was responsible for constructing them. Later observers have found little evidence of such markedly linear features, and Mariner and Viking images show no trace of them; they are now dismissed as optical effects.

A Spanish national facility, planned for construction at the Observatorio del Roque de los Muchachos in the Canary Islands, with completion early in the 21st century. The design is for an optical/infrared reflector, with a segmented mirror of 36 hexagonal components equivalent to a 10-metre 33-foot single mirror similar to the telescopes of the Keck Observatory.

A zodiacal constellation, among those listed by Ptolemy c. AD 140. It is said to represent the crab crushed under the foot of Hercules when he was fighting the Hydra. None of the stars is brighter than fourth magnitude, though the star cluster Praesepe at the constellation’s centre can be seen with the unaided eye.

A small constellation of the northern sky, lying between Boötes and Ursa Major. It was introduced by Johannes Hevelius in the late seventeenth century and is supposed to represent the dogs Asterion and Chara held on a leash by Boötes. Though small, the constellation contains several interesting objects including the bright star Cor Caroli, the fine globular cluster M3 and the Whirlpool Galaxy.

A small constellation, just south of the celestial equator and next to Orion, containing the brightest star in the sky, Sirius. It is said to represent one of the dogs following the hunter, Orion, and was listed by Ptolemy c. AD 140.

A small constellation bordering the celestial equator and close to Orion. With Canis Major, it is supposed to represent one of the dogs following Orion, and was listed by Ptolemy c. AD 140. It contains only two bright stars, the brightest being Procyon.

An informal description sometimes applied to the phenomena of a small galaxy being absorbed by a larger companion galaxy, or a star being merged into another.

The brightest star in the constellation Carina and the second-brightest star in the sky. Canopus is a supergiant F star of magnitude -0.7. The name is that of the pilot of the fleet of King Menelaos of Greek mythology.

The location in Florida, USA, of the Kennedy Space Center, from where most of NASA’s space missions are launched.

The name by which Cape Canaveral was known between 1963 and 1973.

A general catalogue of 455,000 southern stars down to tenth magnitude, compiled at the Cape of Good Hope by J. C. Kapteyn 1851-1922 from photographic plates taken by Sir David Gill 1843-1914. The catalogue covers declinations from -19° to the south celestial pole and was produced between 1896 and 1900.

The brightest star in the constellation Auriga. It is a spectroscopic binary, the primary being a giant G star of magnitude 0.1. The name, of Latin origin, means little she-goat.

One of the zodiacal constellations recorded by Ptolemy c. AD 140. Its brightest stars are third magnitude.

A planetary atmosphere that was created by accretion as part of the planetary formation process and subsequently retained.

synchronous rotation.