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| Names | Sun, Sol (/ˈsɒl/),[1] Sól, Helios (/ˈhiːliəs/)[2] |
|---|---|
| Adjectives | Solar (/ˈsoʊlər/)[3] |
| Symbol | .svg){kind=small} |
| Observation data | |
| Mean distance from Earth | 1 AU ≈ 1.496×108 km[4] 8 min 19 s at light speed |
| Visual brightness (V) | −26.74[5] |
| Absolute magnitude | 4.83[5] |
| Spectral classification | G2V[6] |
| Metallicity | Z = 0.0122[7] |
| Angular size | 31.6–32.7 minutes of arc[8] 0.527–0.545 degrees |
| Orbital characteristics | |
| Mean distance from Milky Way core | ≈26,660 light-years |
| Galactic period | (2.25–2.50)×108 yr |
| Velocity | ≈251 km/s (orbit around the center of the Milky Way) ≈ 20 km/s (relative to average velocity of other stars in stellar neighborhood) ≈ 370 km/s[9] (relative to the cosmic microwave background) |
| Physical characteristics | |
| Equatorial radius | 695,700 km,[10] 696,342 km[11] 109 × Earth radii[12] |
| Equatorial circumference | 4.379×106 km[12] 109 × Earth[12] |
| Flattening | 9×10−6 |
| Surface area | 6.09×1012 km2[12] 12,000 × Earth[12] |
| Volume | 1.41×1018 km3[12] 1,300,000 × Earth |
| Mass | 1.9885×1030 kg[5] 332,950 Earths[5] |
| Average density | 1.408 g/cm3[5][12][13] 0.255 × Earth[5][12] |
| Center density (modeled) | 162.2 g/cm3[5] 12.4 × Earth |
| Equatorial surface gravity | 274 m/s2[5] 28 × Earth[12] |
| Moment of inertia factor | 0.070[5] (estimate) |
| Escape velocity (from the surface) | 617.7 km/s[12] 55 × Earth[12] |
| Temperature | Center (modeled): 1.57×107 K[5] Photosphere (effective): 5,772 K[5] Corona: ≈ 5×106 K |
| Luminosity (Lsol) | 3.828×1026 W[5] ≈ 3.75×1028 lm ≈ 98 lm/W efficacy |
| Color (B-V) | 0.63 |
| Mean radiance (Isol) | 2.009×107 W·m−2·sr−1 |
| Age | ≈4.6 billion years (4.6×109 years)[14][15] |
| Photospheric composition (by mass) | |
| Rotation characteristics | |
| Obliquity | 7.25°[5] (to the ecliptic) 67.23° (to the galactic plane) |
| Right ascension of North pole[17] | 286.13° 19 h 4 min 30 s |
| Declination of North pole | +63.87° 63° 52' North |
| Sidereal rotation period | 25.05 days at equator 25.38 days at 16° latitude 34.4 days at poles[5] |
| Rotation velocity (at equator) | 1.997 km/s[12] |
The Sun is the star at the center of the Solar System. It is a massive, hot ball of plasma, inflated and heated by energy produced by nuclear fusion reactions at its core. Part of this internal energy is emitted from its surface as light, ultraviolet, and infrared radiation, providing most of the energy for life on Earth.
The Sun moves around the Galactic Center of the Milky Way, at a distance of 26,660 light-years. From Earth, it is on average 1 AU (1.496×108 km) or about 8 light-minutes away. Its diameter is about 1,391,400 km (864,600 mi; 4.64 ls), 109 times that of Earth or 4 lunar distances. Its mass is about 330,000 times that of Earth, making up about 99.86% of the total mass of the Solar System.[18] 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.[19]
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][14][20] 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. It is thought that almost all stars form by this process.
Every second, the Sun's core fuses about 600 million tons of hydrogen into helium, and in the process converts 4 million tons of matter into energy. This energy, which can take between 10,000 and 170,000 years to escape the core, is the source of the Sun's light and heat. Far in the future, 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 push 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 this, 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 still glow and give off heat from its previous fusion for trillions of years. After that it might become a super dense hypothetical black dwarf, giving off no more energy.
The enormous effect of the Sun on Earth has been recognized since prehistoric times; the Sun was thought of by some cultures as a deity. The synodic rotation of Earth and its orbit around the Sun are the basis of some solar calendars. The predominant calendar in use today is the Gregorian calendar, which is based upon the standard 16th-century interpretation of the Sun's observed movement as actual movement.[21]
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OED2was invoked but never defined (see the help page). - ^ 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.
- ^ 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.
- ^ 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.
- ^ 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. S2CID 123824232.
- ^ "Eclipse 99: Frequently Asked Questions". NASA. Archived from the original on 27 May 2010. Retrieved 24 October 2010.
- ^ Hinshaw, G.; 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.
- ^ Mamajek, E.E.; Prsa, A.; Torres, G.; et, al. (2015), "IAU 2015 Resolution B3 on Recommended Nominal Conversion Constants for Selected Solar and Planetary Properties", arXiv:1510.07674 [astro-ph.SR]
- ^ Emilio, Marcelo; Kuhn, Jeff R.; Bush, Rock I.; Scholl, Isabelle F. (2012), "Measuring the Solar Radius from Space during the 2003 and 2006 Mercury Transits", The Astrophysical Journal, 750 (2): 135, arXiv:1203.4898, Bibcode:2012ApJ...750..135E, doi:10.1088/0004-637X/750/2/135, S2CID 119255559
- ^ a b c d e f g h i j k l "Solar System Exploration: Planets: Sun: Facts & Figures". NASA. Archived from the original on 2 January 2008.
- ^ Ko, M. (1999). Elert, G. (ed.). "Density of the Sun". The Physics Factbook. Archived from the original on 13 July 2019. Retrieved 14 July 2014.
- ^ a b 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.
- ^ Connelly, JN; Bizzarro, M; Krot, AN; Nordlund, Å; Wielandt, D; Ivanova, MA (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)
- ^ "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.
- ^ Seidelmann, P.K.; et al. (2000). "Report Of The IAU/IAG Working Group On Cartographic Coordinates And Rotational Elements Of The Planets And Satellites: 2000". Archived from the original on 12 May 2020. Retrieved 22 March 2006.
- ^ Woolfson, M. (2000). "The origin and evolution of the solar system" (PDF). Astronomy & Geophysics. 41 (1): 12. Bibcode:2000A&G....41a..12W. doi:10.1046/j.1468-4004.2000.00012.x. Archived (PDF) from the original on 11 July 2020. Retrieved 12 April 2020.
- ^ Basu, S.; Antia, H.M. (2008). "Helioseismology and Solar Abundances". Physics Reports. 457 (5–6): 217–283. arXiv:0711.4590. Bibcode:2008PhR...457..217B. doi:10.1016/j.physrep.2007.12.002. S2CID 119302796.
- ^ Connelly, James N.; Bizzarro, Martin; Krot, Alexander N.; Nordlund, Åke; Wielandt, Daniel; Ivanova, Marina 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.
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