The stars. A star is a luminous sphere of plasma held together by its own gravity. The nearest star to Eart is the sun. Many 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 constellation and asteried, the brightest of which gained proper names. Astronomers have assembled star catalogue that identify the known stars and provide standardized stellar designetion. However, most of the stars in the universe, including all stars outside our galaxi, the Milky way, are invisible to the naked eye from Earth. Indeed, most are invisible from Earth even through the most powerful telescopes.