A project by California Institute of Technology and the Massachusetts Institute of Technology to construct a detector of gravitational waves in the USA. It will consist of detectors in Washington State and Louisiana. Each L-shaped installation will beam laser light down 4-kilometre-long 2.5-mile, evacuated tubes. Changes in the length of the light path caused by gravitational waves should register in the detectors.

satellite laser ranging.

The phase of the Moon when it is waning towards new Moon and appears as an illuminated semicircle. Last quarter is formally defined as the time when the Moon’s celestial longitude is 270° greater than the Sun’s. It occurs about seven days after full Moon.

A relatively cool star, such as one of spectral type K or M. The nomenclature is misleading, dating from a time when the main sequence of the Hertzsprung-Russell diagram was thought to be an evolutionary track. It is, nevertheless, still in widespread use. Hot stars are described as early in this nomenclature.

Angular distance north or south of the equator in a spherical coordinate system. In celestial equatorial coordinates, the counterpart of latitude is declination.

Abbreviation for Large Binocular Telescope.

Abbreviation for Long Duration Exposure Facility.

Universal Time.

A year containing 366 days instead of the normal 365. Leap years are a feature of the Julian calendar and the Gregorian calendar and were introduced to ensure that the calendar year keeps step with the seasons.

A small satellite of Jupiter number XIII, discovered by Charles Kowal in 1974. It is only about 15 kilometres across and belongs to a group of four satellites whose closely spaced orbits all lie between 11.1 and 11.7 million kilometres from Jupiter. The others are Himalia, Lysithea and Elara.

A model of the universe that begins with a Big Bang, has a static phase and then expands indefinitely. It is named after Georges Lemaître 1894-1966, who in 1927 published a major work on the expansion of the universe. He was the first to advocate expansion from a primeval atom, while Einstein was still propounding the merits of a static universe.

A transparent optical device that changes the directional properties of a beam of light passing through it. Different types of lens are designed for different purposes. Convex and biconvex lenses cause a parallel beam of light to converge at the focal point. Concave and biconcave lenses diverge a parallel beam. Lenses are frequently used in combination to achieve results unobtainable with a single lens, for example in a telescope eyepiece. Elements may be cemented together: doublets and triplets are lenses composed of two and three elements, respectively. Such combinations, made from lenses of different types of glass, are used to minimize chromatic aberration. The objective lens of a refracting telescope is its light-gathering element.

A galaxy of type S0 in the Hubble classification, intermediate between elliptical and spiral types, so named because the apparent shape of such galaxies resembles a convex lens.

One of the twelve zodiacal constellations, included by Ptolemy in his list of 48 c. AD 140. The pattern made by the brightest stars of this large and conspicuous constellation bear some resemblance to the outline of a lion in profile. The asterism outlining the head is known as the Sickle. There are ten stars brighter than fourth magnitude, the brightest being Regulus and Denebola. Leo also contains numerous galaxies, including five from the Messier Catalogue M65, M66, M95, M96 and M105.

A small and very inconspicuous constellation between Leo and Ursa Major. It was introduced by Johannes Hevelius in the late seventeenth century and contains only one star brighter than fourth magnitude.