A type of telescopic eyepiece with a planoconvex field lens and an achromatic doublet as an eyelens. It is generally regarded as a good all-purpose eyepiece and is widely used.

The SI unit in which temperature is measured. It is defined formally as the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. One kelvin corresponds to an interval of one degree on the Celsius scale. The kelvin temperature scale starts from absolute zero, which is -273.16°C.

The primary space launch facility of the US National Aeronautics and Space Administration NASA, located at Cape Canaveral on the Atlantic coast of Florida. It is the sole location from which the Space Shuttle has been launched, and is one of the few facilities at which a Shuttle has landed. In the past, all the manned launches in the Mercury, Gemini, Apollo and Skylab programmes took place as KSC. Many unmanned expendable vehicles, such as Delta rockets, are also launched from KSC. It was named after the late US President John F. Kennedy.

A lunar crater, 32 kilometres 20 miles in diameter, in the Oceanus Procellarum. It has terraced walls and a central peak, and is the centre of a large, bright ray system.

Kepler is a space observatory planned by NASA that will search for extrasolar planets. For this purpose, it will observe the brightness of about 100,000 stars over four years to detect periodical transits of a star by one of its planets. Kepler will not be in an Earth orbit but in an Earth-trailing solar orbit so that Earth will not hide the stars which are to be observed and the photometer will not be influenced by stray light from Earth. The observatory is currently scheduled for launch in November 2008, though there is a high probability of change in the launch date as it has already changed a number of times.

The probe is estimated to weigh 995 kg, have a 0.95 meter photometer, have a field of view of roughly two hands held at arm's length, will take un-focused "pictures" every three seconds, and will cost an estimated $467 million.

anomaly.

Three fundamental statements about planetary motion, derived empirically by Johannes Kepler 1571-1630 on the basis of detailed observations of the planets made by Tycho Brahe 1546-1601: 1. The orbit of each planet is an ellipse with the Sun at one of the foci. 2. Each planet orbits the Sun such that the radius vector connecting the planet and the Sun sweeps out equal areas in equal times. 3. The squares of the sidereal periods of any two planets are proportional to the cubes of their mean distances from the Sun. The first two were published in 1609 in Astronomia Nova and the third in 1619 in Harmonice mundi. The physical basis for the laws was not understood until Isaac Newton 1642-1727 formulated his law of gravity.

A supernova in the constellation Ophiuchus in October 1604. It was observed and its position determined by Johannes Kepler. It reached a maximum magnitude of about -2.5 and the light curve shows it to have been a Type I supernova. The remnant is a source of radio emission, and a faint optical remnant has also been identified.

A simple telescope in which convex lenses are used as both objective and eyepiece. This gives a larger field of view and higher magnification than the Galilean telescope, but the image is inverted.

A solution discovered by Roy Kerr in 1963 of Einstein’s equations for the spacetime of a rotating black hole. The Kerr metric shows that about half the mass of a black hole can theoretically be extracted as rotational energy. This is of significant importance in models of quasars and active galactic nuclei that invoke rotating black holes as the central engine. See also: metric.

A dark dust nebula near the centre of the Eta Carinae Nebula. The name comes from the shape. The eye of the keyhole is a bubble expanding at 40 km/s.

An asterism formed by the four stars ε Epsilon, ζ Zeta, η Eta and π Pi in the constellation Hercules.

The group of three stars ε Epsilon, ζ Zeta and η Eta in the constellation Auriga.

A unit of distance equal to one thousand parsecs, which is 3,261.61 light years.

The mathematical analysis of movement, without reference to mass or force.