Search results
Results From The WOW.Com Content Network
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.
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
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]
This core convection occurs in stars where the CNO cycle contributes more than 20% of the total energy. As the star ages and the core temperature increases, the region occupied by the convection zone slowly shrinks from 20% of the mass down to the inner 8% of the mass. [25] The Sun produces on the order of 1% of its energy from the CNO cycle.
Main-sequence stars vary in surface temperature from approximately 2,000 to 50,000 K, whereas more-evolved stars – in particular, newly-formed white dwarfs – can have surface temperatures above 100,000 K. [3] Physically, the classes indicate the temperature of the star's atmosphere and are normally listed from hottest to coldest.
The internal structure of a main sequence star depends upon the mass of the star. In stars with masses of 0.3–1.5 solar masses (M ☉), including the Sun, hydrogen-to-helium fusion occurs primarily via proton–proton chains, which do not establish a steep temperature gradient. Thus, radiation dominates in the inner portion of solar mass stars.
Cecilia Payne-Gaposchkin (born Cecilia Helena Payne; () May 10, 1900 – () December 7, 1979) was a British-American astronomer and astrophysicist.In her 1925 doctoral thesis she proposed that stars were composed primarily of hydrogen and helium. [1]
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