A mathematical formula that gives approximations to the distances of the planets from the Sun starting with only the number in order of sequence. The relationship takes the form: D = 0.4 + 0.3×N where D is the distance in astronomical units AU and N takes the VALUES (0, 1, 2, 4, 8..., doubling for each successive planet. The relationship holds to within a few per cent for the seven innermost major planets as long as the value N=8 is taken to represent the largest asteroid, Ceres. However, it breaks down seriously for Neptune and Pluto. The formula was devised in 1766 by J. Titius and copied a few years later by J. E. Bode, who published it. At that time none of the asteroids had been discovered, and the gap at 2.8 AU, where the formula predicted that there should be a planet, convinced astronomers that a small planet would be found there, which indeed proved to be the case.

Abbreviation for transient lunar phenomenon.

The former name of a research institute of the University of Tokyo, which, in a reorganization in 1988, was largely incorporated into the new National Astronomical Observatory of Japan, funded by the Ministry of Education, Science and Culture. The new body has its headquarters at the address of the former Tokyo Astronomical Observatory and also incorporates the Okayama Astrophysical Observatory, Dodaira Observatory, Norikura Corona Observing Station and Nobeyama Radio Observatory. Its 8-metre 300-inch optical/infrared instrument, the Subaru telescope at the Mauna Kea Observatories in Hawaii, is due to be opened in 1999.

A type of telescope eyepiece constructed from a single solid cylinder of glass.

The coordinates of a celestial body measured from the Earth’s surface in contrast with geocentric coordinates, which are corrected to correspond to hypothetical observation from the Earth’s centre.

A radio source in the direction of the galactic centre, the nature of which remains unknown. The name is derived from the appearance of the radiograph of the source.

Asteroid 1685, diameter 7.6 km, discovered in 1948 by A. Wirtanen. It is a member of the Apollo group of asteroids and periodically makes exceptionally close approaches to Earth.

A three-dimensional ring shape, such as that of a ring doughnut or quoit; the orbit of Io around Jupiter is enclosed in a plasma torus.

The phase in the course of a solar or lunar eclipse during which the Sun is totally obscured or the Moon totally in the Earth’s shadow.

English name for the constellation Tucana.

Asteroid 4179, an Earth-crossing asteroid discovered in 1989. Radar studies have shown it be irregular, measuring 4.7 by 2.4 by 1.9 km 2.9 by 1.5 by 1.2 miles and have revealed the presence of craters and ridges on the surface. There is some suggestion that it may in fact be two bodies in close proximity. It rotates in a very complex manner. Both its shape and rotation are thought to be the result of collisions with other bodies. The plane of Toutatis’s orbit is closer to the plane of Earth’s orbit than that of any other known Earth-crossing asteroid. It makes a close approach to Earth in 2004, passing at about four times the Moon’s distance.

A network of four satellites, launched from Space Shuttles in 1983, 1986, 1988 and 1989, used to track NASA spacecraft and relay their data and commands more efficiently than is possible with a ground-based tracking network. It is the first space-based global tracking system.

A phenomenon of brief duration.

Alleged temporary appearance of coloured patches or obscuration on the surface of the Moon. Reported observations are associated particularly with the regions of the craters Aristarchus, Gassendi and Alphonsus. It remains unclear whether real physical phenomena have been observed.

The passage of a star or other celestial object across the observer’s meridian in the course of the daily apparent motion of the celestial sphere.