Sun

"The Sun" redirects here. For other uses, see Sun (disambiguation) and The Sun (disambiguation).

Sun
White glowing ball with black sunspots
The Sun, viewed through a clear solar filter
NamesSun, Sol,[1] Sól, Helios[2]
AdjectivesSolar[3]
SymbolCircle with dot in the middle
Observation data
Mean distance from Earth1 AU
149,600,000 km
8 min 19 s, light speed[4]
−26.74 (V)[5]
4.83[5]
G2V[6]
MetallicityZ = 0.0122[7]
Angular size0.527–0.545°[8]
Orbital characteristics
Mean distance from Milky Way core
24,000 to 28,000 light-years[9]
Galactic period225–250 million years
Velocity
Obliquity
Right ascension North pole
286.13° (286° 7′ 48″)[5]
Declination of North pole
+63.87° (63° 52′ 12"N)[5]
  • 25.05 days (equator)
  • 34.4 days (poles)[5]
Equatorial rotation velocity
1.997 km/s[11]
Physical characteristics
Equatorial radius
6.957×108 m[12]
109 × Earth radii[11]
Flattening0.00005[5]
Surface area6.09×1012 km2
12,000 × Earth[11]
Volume
  • 1.412×1018 km3
  • 1,300,000 × Earth
Mass
Average density1.408 g/cm3
0.255 × Earth[5][11]
Age4.6 billion years[13][14]
Equatorial surface gravity
274 m/s2[5]
27.9 g0[11]
≈0.070[5]
617.7 km/s
55 × Earth[11]
Temperature
Luminosity
Color (B-V)0.656[15]
Mean radiance2.009×107 W·m−2·sr−1
Photosphere composition by mass

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. It is by far the most important source of energy for life on Earth. The Sun has been an object of veneration in many cultures. It has been a central subject for astronomical research since antiquity.

The Sun orbits the Galactic Center at a distance of 24,000 to 28,000 light-years. From Earth, it is 1 astronomical unit (1.496×108 km) or about 8 light-minutes away. Its diameter is about 1,391,400 km (864,600 mi), 109 times that of Earth. Its mass is about 330,000 times that of Earth, making up about 99.86% of the total mass of the Solar System. Roughly three-quarters of the Sun's mass consists of hydrogen (~73%); the rest is mostly helium (~25%), with much smaller quantities of heavier elements, including oxygen, carbon, neon, and iron.

The Sun is a G-type main-sequence star (G2V), informally called a yellow dwarf, though its light is actually white. It formed approximately 4.6 billion[a] years ago from the gravitational collapse of matter within a region of a large molecular cloud. Most of this matter gathered in the center, whereas the rest flattened into an orbiting disk that became the Solar System. The central mass became so hot and dense that it eventually initiated nuclear fusion in its core. Every second, the Sun's core fuses about 600 billion kilograms (kg) of hydrogen into helium and converts 4 billion kg of matter into energy.

About 4 to 7 billion years from now, when hydrogen fusion in the Sun's core diminishes to the point where the Sun is no longer in hydrostatic equilibrium, its core will undergo a marked increase in density and temperature which will cause its outer layers to expand, eventually transforming the Sun into a red giant. This process will make the Sun large enough to render Earth uninhabitable approximately five billion years from the present. After the red giant phase, models suggest the Sun will shed its outer layers and become a dense type of cooling star (a white dwarf), and no longer produce energy by fusion, but will still glow and give off heat from its previous fusion for perhaps trillions of years. After that, it is theorized to become a super dense black dwarf, giving off negligible energy.

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  2. ^ Cite error: The named reference Lexico was invoked but never defined (see the help page).
  3. ^ Cite error: The named reference OED2 was invoked but never defined (see the help page).
  4. ^ Pitjeva, E. V.; Standish, E. M. (2009). "Proposals for the masses of the three largest asteroids, the Moon–Earth mass ratio and the Astronomical Unit". Celestial Mechanics and Dynamical Astronomy. 103 (4): 365–372. Bibcode:2009CeMDA.103..365P. doi:10.1007/s10569-009-9203-8. ISSN 1572-9478. S2CID 121374703. Archived from the original on 9 July 2019. Retrieved 13 July 2019.
  5. ^ a b c d e f g h i j k l m n Williams, D. R. (1 July 2013). "Sun Fact Sheet". NASA Goddard Space Flight Center. Archived from the original on 15 July 2010. Retrieved 12 August 2013.
  6. ^ Zombeck, Martin V. (1990). Handbook of Space Astronomy and Astrophysics 2nd edition. Cambridge University Press. Archived from the original on 3 February 2021. Retrieved 13 January 2016.
  7. ^ Asplund, M.; Grevesse, N.; Sauval, A. J. (2006). "The new solar abundances – Part I: the observations". Communications in Asteroseismology. 147: 76–79. Bibcode:2006CoAst.147...76A. doi:10.1553/cia147s76. ISSN 1021-2043. S2CID 123824232.
  8. ^ "Eclipse 99: Frequently Asked Questions". NASA. Archived from the original on 27 May 2010. Retrieved 24 October 2010.
  9. ^ Francis, Charles; Anderson, Erik (June 2014). "Two estimates of the distance to the Galactic Centre". Monthly Notices of the Royal Astronomical Society. 441 (2): 1105–1114. arXiv:1309.2629. Bibcode:2014MNRAS.441.1105F. doi:10.1093/mnras/stu631. S2CID 119235554.
  10. ^ Hinshaw, G.; Weiland, J. L.; Hill, R. S.; Odegard, N.; Larson, D.; et al. (2009). "Five-year Wilkinson Microwave Anisotropy Probe observations: data processing, sky maps, and basic results". The Astrophysical Journal Supplement Series. 180 (2): 225–245. arXiv:0803.0732. Bibcode:2009ApJS..180..225H. doi:10.1088/0067-0049/180/2/225. S2CID 3629998.
  11. ^ a b c d e f "Solar System Exploration: Planets: Sun: Facts & Figures". NASA. Archived from the original on 2 January 2008.
  12. ^ a b Prša, Andrej; Harmanec, Petr; Torres, Guillermo; et al. (1 August 2016). "NOMINAL VALUES FOR SELECTED SOLAR AND PLANETARY QUANTITIES: IAU 2015 RESOLUTION B3 * †". The Astronomical Journal. 152 (2): 41. arXiv:1510.07674. doi:10.3847/0004-6256/152/2/41. ISSN 0004-6256.
  13. ^ Bonanno, A.; Schlattl, H.; Paternò, L. (2002). "The age of the Sun and the relativistic corrections in the EOS". Astronomy and Astrophysics. 390 (3): 1115–1118. arXiv:astro-ph/0204331. Bibcode:2002A&A...390.1115B. doi:10.1051/0004-6361:20020749. S2CID 119436299.
  14. ^ Connelly, J. N.; Bizzarro, M.; Krot, A. N.; Nordlund, Å.; Wielandt, D.; Ivanova, M. A. (2 November 2012). "The Absolute Chronology and Thermal Processing of Solids in the Solar Protoplanetary Disk". Science. 338 (6107): 651–655. Bibcode:2012Sci...338..651C. doi:10.1126/science.1226919. PMID 23118187. S2CID 21965292.(registration required)
  15. ^ Gray, David F. (November 1992). "The Inferred Color Index of the Sun". Publications of the Astronomical Society of the Pacific. 104 (681): 1035–1038. Bibcode:1992PASP..104.1035G. doi:10.1086/133086.
  16. ^ "The Sun's Vital Statistics". Stanford Solar Center. Archived from the original on 14 October 2012. Retrieved 29 July 2008. Citing Eddy, J. (1979). A New Sun: The Solar Results From Skylab. NASA. p. 37. NASA SP-402. Archived from the original on 30 July 2021. Retrieved 12 July 2017.


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