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Solar System

For other uses, see Solar System (disambiguation).

Solar System
The Sun, planets, moons and dwarf planets[a]
(true color, size to scale, distances not to scale)
Age4.568 billion years[b]
Location
Nearest star
Population
StarsSun
Planets
Known dwarf planets
Known natural satellites758[D 3]
Known minor planets1,368,528[D 4]
Known comets4,591[D 4]
Planetary system
Star spectral typeG2V
Frost line~5 AU[5]
Semi-major axis of outermost planet30.07 AU[D 5] (Neptune)
Kuiper cliff50–70 AU[3][4]
Heliopausedetected at 120 AU[6]
Hill sphere1.1 pc (230,000 AU)[7] – 0.865 pc (178,419 AU)[8]
Orbit about Galactic Center
Invariable-to-galactic plane inclination~60°, to the ecliptic[c]
Distance to
Galactic Center
24,000–28,000 ly
[9]
Orbital speed
720,000 km/h (450,000 mi/h)[10]
Orbital period~230 million years[10]

The Solar System[d] consists of the Sun and the objects that orbit it.[11] The name comes from Sōl, the Latin name for the Sun.[12] It formed about 4.6 billion years ago when a dense region of a molecular cloud collapsed, creating the Sun and a protoplanetary disc from which the orbiting bodies assembled. The fusion of hydrogen into helium inside the Sun's core releases energy, which is primarily emitted through its outer photosphere. This creates a decreasing temperature gradient across the system. Over 99.86% of the Solar System's mass is located within the Sun.

The most massive objects that orbit the Sun are the eight planets. Closest to the Sun in order of increasing distance are the four terrestrial planets – Mercury, Venus, Earth and Mars. Only the Earth and Mars orbit within the Sun's habitable zone, where liquid water can exist on the surface. Beyond the frost line at about five astronomical units (AU),[e] are two gas giants – Jupiter and Saturn – and two ice giants – Uranus and Neptune. Jupiter and Saturn possess nearly 90% of the non-stellar mass of the Solar System.

There are a vast number of less massive objects. There is a strong consensus among astronomers that the Solar System has at least nine dwarf planets: Ceres, Orcus, Pluto, Haumea, Quaoar, Makemake, Gonggong, Eris, and Sedna.[f] Six planets, seven dwarf planets, and other bodies have orbiting natural satellites, which are commonly called 'moons', and range from sizes of dwarf planets, like Earth's Moon, to moonlets. There are small Solar System bodies, such as asteroids, comets, centaurs, meteoroids, and interplanetary dust clouds. Some of these bodies are in the asteroid belt (between Mars's and Jupiter's orbit) and the Kuiper belt (just outside Neptune's orbit).[g]

Between the bodies of the Solar System is an interplanetary medium of dust and particles. The Solar System is constantly flooded by outflowing charged particles from the solar wind, forming the heliosphere. At around 70–90 AU from the Sun, the solar wind is halted by the interstellar medium, resulting in the heliopause. This is the boundary to interstellar space. The Solar System extends beyond this boundary with its outermost region, the theorized Oort cloud, the source for long-period comets, extending to a radius of 2,000–200,000 AU. The Solar System currently moves through a cloud of interstellar medium called the Local Cloud. The closest star to the Solar System, Proxima Centauri, is 4.25 light-years (269,000 AU) away. Both are within the Local Bubble, a relatively small 1,000 light-years wide region of the Milky Way.


Cite error: There are <ref group=lower-alpha> tags or {{efn}} templates on this page, but the references will not show without a {{reflist|group=lower-alpha}} template or {{notelist}} template (see the help page).

  1. ^ "Our Local Galactic Neighborhood". interstellar.jpl.nasa.gov. Interstellar Probe Project. NASA. 2000. Archived from the original on 21 November 2013. Retrieved 8 August 2012.
  2. ^ Hurt, R. (8 November 2017). "The Milky Way Galaxy". science.nasa.gov. Retrieved 19 April 2024.
  3. ^ Chiang, E. I.; Jordan, A. B.; Millis, R. L.; et al. (2003). "Resonance Occupation in the Kuiper Belt: Case Examples of the 5:2 and Trojan Resonances". The Astronomical Journal. 126 (1): 430–443. arXiv:astro-ph/0301458. Bibcode:2003AJ....126..430C. doi:10.1086/375207. S2CID 54079935.
  4. ^ de la Fuente Marcos, C.; de la Fuente Marcos, R. (January 2024). "Past the outer rim, into the unknown: structures beyond the Kuiper Cliff". Monthly Notices of the Royal Astronomical Society Letters. 527 (1) (published 20 September 2023): L110 – L114. arXiv:2309.03885. Bibcode:2024MNRAS.527L.110D. doi:10.1093/mnrasl/slad132. Archived from the original on 28 October 2023. Retrieved 28 September 2023.
  5. ^ Mumma, M. J.; Disanti, M. A.; Dello Russo, N.; et al. (2003). "Remote infrared observations of parent volatiles in comets: A window on the early solar system". Advances in Space Research. 31 (12): 2563–2575. Bibcode:2003AdSpR..31.2563M. CiteSeerX 10.1.1.575.5091. doi:10.1016/S0273-1177(03)00578-7.
  6. ^ Greicius, Tony (5 May 2015). "NASA Spacecraft Embarks on Historic Journey Into Interstellar Space". nasa.gov. Archived from the original on 11 June 2020. Retrieved 19 April 2024.
  7. ^ Chebotarev, G. A. (1 January 1963). "Gravitational Spheres of the Major Planets, Moon and Sun". Astronomicheskii Zhurnal. 40: 812. Bibcode:1964SvA.....7..618C. ISSN 0004-6299. Archived from the original on 7 May 2024. Retrieved 6 May 2024.
  8. ^ Souami, D; Cresson, J; Biernacki, C; Pierret, F (21 August 2020). "On the local and global properties of gravitational spheres of influence". Monthly Notices of the Royal Astronomical Society. 496 (4): 4287–4297. arXiv:2005.13059. doi:10.1093/mnras/staa1520.
  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. ^ a b "Sun: Facts". science.nasa.gov. 14 November 2017. Archived from the original on 19 April 2024. Retrieved 19 April 2024.
  11. ^ "IAU Office of Astronomy for Education". astro4edu.org. IAU Office of Astronomy for Education. Archived from the original on 11 December 2023. Retrieved 11 December 2023.
  12. ^ Cite error: The named reference k349 was invoked but never defined (see the help page).
  13. ^ Standish, E. M. (April 2005). "The Astronomical Unit now". Proceedings of the International Astronomical Union. 2004 (IAUC196): 163–179. Bibcode:2005tvnv.conf..163S. doi:10.1017/S1743921305001365. S2CID 55944238.


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