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Solar radius is a unit of distance used to express the size of stars in astronomy relative to the Sun. The solar radius is usually defined as the radius to the layer in the Sun 's photosphere where the optical depth equals 2/3: [1] 695,700 kilometres (432,300 miles) is approximately 10 times the average radius of Jupiter, 109 times the radius ...
The Sun is the star at the center of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light and infrared radiation with 10% at ultraviolet energies.
The nominal solar mass parameter can be combined with the most recent (2014) CODATA estimate of the Newtonian constant of gravitation G to derive the solar mass to be approximately 1.9885 × 10 30 kg. Although the exact values for the luminosity, radius, mass parameter, and mass may vary slightly in the future due to observational uncertainties ...
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
Heat Death As expansion continues, the universe becomes larger, colder, and more dilute; in time, all structures eventually decompose to subatomic particles and photons. In the case of indefinitely continuing cosmic expansion, the energy density in the universe will decrease until, after an estimated time of 10 1000 years, it reaches ...
The closest encounter to the Sun so far predicted is the low-mass orange dwarf star Gliese 710 / HIP 89825 with roughly 60% the mass of the Sun. [4] It is currently predicted to pass 0.1696 ± 0.0065 ly (10 635 ± 500 au) from the Sun in 1.290 ± 0.04 million years from the present, close enough to significantly disturb the Solar System's Oort ...
Solar core. The core of the Sun is considered to extend from the center to about 0.2 of the solar radius (139,000 km; 86,000 mi). [1] It is the hottest part of the Sun and of the Solar System. It has a density of 150,000 kg/m 3 (150 g/cm 3) at the center, and a temperature of 15 million kelvins (15 million degrees Celsius; 27 million degrees ...
Image of Sirius A and Sirius B taken by the Hubble Space Telescope. Sirius B, which is a white dwarf, can be seen as a faint point of light to the lower left of the much brighter Sirius A. A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun 's ...