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A star is a luminous spheroid of plasma held together by self-gravity. [1] The nearest star to Earth is the Sun.Many other stars are visible to the naked eye at night; their immense distances from Earth make them appear as fixed points of light.
Later in its life, a low-mass star will slowly eject its atmosphere via stellar wind, forming a planetary nebula, while a higher–mass star will eject mass via a sudden catastrophic event called a supernova. The term supernova nucleosynthesis is used to describe the creation of elements during the explosion of a massive star or white dwarf.
Although the Sun is a star, its photosphere has a low enough temperature of 6,000 K (5,730 °C; 10,340 °F), and therefore molecules can form. Water has been found on the Sun, and there is evidence of H 2 in white dwarf stellar atmospheres. [2] [4] Cooler stars include absorption band spectra that are
Stellar structure models describe the internal structure of a star in detail and make predictions about the luminosity, the color and the future evolution of the star. Different classes and ages of stars have different internal structures, reflecting their elemental makeup and energy transport mechanisms.
Representative lifetimes of stars as a function of their masses The change in size with time of a Sun-like star Artist's depiction of the life cycle of a Sun-like star, starting as a main-sequence star at lower left then expanding through the subgiant and giant phases, until its outer envelope is expelled to form a planetary nebula at upper right Chart of stellar evolution
The Sun is a G-type main-sequence star that makes up about 99.86% of the mass of the Solar System. [26] It has an absolute magnitude of +4.83, estimated to be brighter than about 85% of the stars in the Milky Way, most of which are red dwarfs. [27] [28] It is more massive than 95% of the stars within 7 pc (23 ly). [29]
Starlight is the light emitted by stars. [1] It typically refers to visible electromagnetic radiation from stars other than the Sun, observable from Earth at night, although a component of starlight is observable from Earth during daytime. Sunlight is the term used for the Sun's starlight observed during daytime.
The W51 nebula in Aquila - one of the largest star factories in the Milky Way (August 25, 2020). Star formation is the process by which dense regions within molecular clouds in interstellar space, sometimes referred to as "stellar nurseries" or "star-forming regions", collapse and form stars. [1]