A
star is a luminous sphere of
plasma held together by its own
gravity. The nearest star to
Earth is the
Sun. Other stars are visible to the naked eye from Earth during the night, appearing as a multitude of fixed luminous points in the sky due to their immense distance from Earth. Historically, the most prominent stars were grouped into
constellations and
asterisms, and the brightest stars gained proper names. Extensive
catalogues of stars have been assembled by astronomers, which provide standardized
star designations.