for those objects in both catalogues, light curves and characteristics for about 3000 variable stars, and positions and magnitudes for more than 2000 extragalactic sources used to define the celestial reference frame. The second data release (DR2), which occurred on 25 April 2018, is based on 22 months of observations made between 25 July 2014 and 23 May 2016. It includes positions, parallaxes and proper motions for about 1.3 billion stars and positions of an additional 300 million stars, red and blue photometric data for about 1.1 billion stars and single colour photometry for an additional 400 million stars, and median radial velocities for about 7 million stars between magnitude 4 and 13. It also contains data for over 14,000 selected Solar System objects. The first part of the third data release, EDR3 (Early Data Release 3) was released on 3 December 2020. It is based on 34 months of observations and consists of improved positions, parallaxes and proper motions of over 1.8 billion objects The full DR3, published in June 2022, includes the EDR3 data plus Solar System data; variability information; results for non-single stars, for quasars, and for extended objects; astrophysical parameters; and a special data set, the Gaia Andromeda Photometric Survey (GAPS). The final Gaia catalogue is expected to be released three years after the end of the Gaia mission. Specialized catalogues Specialized catalogues make no effort to list all the stars in the sky, working instead to highlight a particular type of star, such as variables or nearby stars. ADS Aitken's double star catalogue (1932) lists 17,180 double stars north of declination −30 degrees. Carbon stars Stephenson's General Catalogue of galactic Carbon stars is a catalogue of 7000+ carbon stars. Gl, GJ, Wo The Gliese (later Gliese-Jahreiß) catalogue attempts to list all star systems within of Earth ordered by right ascension (see the List of nearest stars and brown dwarfs). Later editions expanded the coverage to . Numbers in the range 1.0–915.0 (Gl numbers) are from the second edition, which was Catalogue of Nearby Stars (1969, W. Gliese). The integers up to 915 represent systems which were in the first edition. Numbers with a decimal point were used to insert new star systems for the second edition without destroying the desired order (by right ascension). This catalogue is referred to as CNS2, although this name is never used in catalogue numbers. Numbers in the range 9001–9850