<P> A star is a luminous sphere of plasma held together by its own gravity . The nearest star to Earth 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 constellations and asterisms, the brightest of which gained proper names . Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations . However, most of the stars in the Universe, including all stars outside our galaxy, the Milky Way, are invisible to the naked eye from Earth . Indeed, most are invisible from Earth even through the most powerful telescopes . </P> <P> For at least a portion of its life, a star shines due to thermonuclear fusion of hydrogen into helium in its core, releasing energy that traverses the star's interior and then radiates into outer space . Almost all naturally occurring elements heavier than helium are created by stellar nucleosynthesis during the star's lifetime, and for some stars by supernova nucleosynthesis when it explodes . Near the end of its life, a star can also contain degenerate matter . Astronomers can determine the mass, age, metallicity (chemical composition), and many other properties of a star by observing its motion through space, its luminosity, and spectrum respectively . The total mass of a star is the main factor that determines its evolution and eventual fate . Other characteristics of a star, including diameter and temperature, change over its life, while the star's environment affects its rotation and movement . A plot of the temperature of many stars against their luminosities produces a plot known as a Hertzsprung--Russell diagram (H--R diagram). Plotting a particular star on that diagram allows the age and evolutionary state of that star to be determined . </P>

What is the typical composition of a star
find me the text answering this question