A meteorite discovered accidentally or fortuitously and recognized as such by its nature, as opposed to one actually seen to fall.

A small telescope attached to the tube of a larger instrument, used for locating the correct field of view. A finder usually incorporates a cross-wire and is aligned so that an object located on the cross-wire appears centrally in the smaller field of view of the main telescope.

A particularly bright meteor. There is no precise definition: magnitudes -3, -4 or -5 are variously quoted as the minimum for a meteor to be described as a fireball. The appearance of a fireball carries some likelihood that a meteorite fall may occur.

Alternative for primeval fireball.

Abbreviation for Far-Infrared and Sub-millimetric Space Telescope.

In an eclipse of the Sun, the point when the Moon’s disc first begins to move across the Sun’s photosphere. In a lunar eclipse, first contact occurs when the Moon enters the full shadow umbra of the Earth. The term may also be used to describe the similar stage in the progress of a transit or occultation. Also a somewhat theoretical term for humans meeting extraterrestrial intelligence for the first time, largely promoted by science fiction novels and movies but whose use is innevitable should the occasion arise.

One of the two points on the celestial sphere where the ecliptic and the celestial equator cross. It is used as the zero point for right ascension. Because of the effects of precession, the equator is slowly sliding around the ecliptic, taking about 25,800 years to make one revolution. Though the intersection point was in the constellation Aries several thousand years ago, it is now in Pisces, but the name has not been changed. The Sun is at the First Point of Aries on the northern vernal equinox, and the expression vernal equinox is also used to describe this place on the celestial sphere.

The phase of the Moon when half the visible disc is illuminated and the Moon is waxing towards full. First quarter occurs when the celestial longitude of the Moon is 90° greater than the Sun’s.

English name for the constellation Pisces.

Abbreviation for the series of fundamental star catalogues published in Germany since 1907. The current version is FK5, published in 1988. See also: fundamental catalogue.

Popular name for IC 405, a star cluster surrounded by nebulosity in Auriga.

Identification numbers assigned to stars listed in Historia coelestis Britannica by John Flamsteed 1646-1719. In the official version of the catalogue, published posthumously in 1725, the numbers are not included explicitly. However, they do appear in a preliminary version published by Edmond Halley and Isaac Newton in 1712 without Flamsteed’s approval. Few copies of this version survive because Flamsteed, greatly angered at the action of Halley and Newton, destroyed many of them. The numbers were allocated by constellation and in order of right ascension. They were subsequently used by other cataloguers, including John Bevis 1750 and J.-J. de Lalande 1783. The Flamsteed numbers are still commonly used for stars that do not also have a Greek Bayer letter designation.

A phenomenon in the solar chromosphere and corona, caused by a sudden release of energy that heats and accelerates matter in the Sun’s atmosphere. Flares are explosions lasting typically for a few minutes, during which matter reaches temperatures of hundreds of millions of degrees. Most of the radiation is emitted as X-rays but flares are more easily observed in visible light or radio waves. They are associated with active regions of the Sun. Charged particles ejected from the Sun by flares cause aurorae when they reach the Earth a few days later.

A dwarf M star that undergoes unpredictable outbursts lasting a few minutes, during which the brightness may increase by a magnitude or more. All flare stars have emission lines in their spectra and the flares are thought to be phenomena in the stellar chromosphere, similar to flares, but far more energetic. The nearest star to the Sun, Proxima Centauri, is a flare star. Flare stars are also known as UV Ceti stars.

The emission line spectrum of the solar chromosphere, observed fleetingly at the onset and conclusion of a total solar eclipse.