A star is a form of a celestial object made up of a shining spheroid of plasma held together by its own gravity. The nearby star to Earth is the Sun. Several other stars are visible to the naked eye from Earth during the night time, looking at a multitude of fixed luminous points in the sky due to their enormous distance from Earth. Historically, the most noticeable stars were grouped into constellations and asterisms, the brightest of which gained proper tags. Astronomers have drawn together star catalogues that identify the known stars and deliver standardized stellar designations. However, it is estimated that there are over 300 sextillions (3×1023) stars in the Universe, including all-stars outside our galaxy (the Milky Way), are invisible to the naked eye from Earth.A star's life stat with the gravitational collapse of a gaseous nebula of material composed mostly of hydrogen, along with helium and small amounts of heavier elements. When the lunar core is sufficiently thick, hydrogen becomes gradually converted into helium through nuclear fusion, liberating energy in the process. The rest of the interior of the star transfers energy away from the core through a mixture of the radiative and convective heat transfer process. The interior pressure prevents it from collapsing further under its own gravity. A star with mass bigger than 0.4 times the Sun's mass will expand to become a red hulk when the hydrogen fuel in its core is exhausted.