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| Age | 4.568 billion years[a] |
|---|---|
| Location | |
| Nearest star |
|
| Population | |
| Stars | Sun |
| Planets | |
| Known dwarf planets | |
| Known natural satellites | 758[D 3] |
| Known minor planets | 1,358,412[D 4] |
| Known comets | 4,591[D 4] |
| Planetary system | |
| Star spectral type | G2V |
| Frost line | ~5 AU[5] |
| Semi-major axis of outermost planet | 30.07 AU[D 5] (Neptune) |
| Kuiper cliff | 50–70 AU[3][4] |
| Heliopause | detected at 120 AU[6] |
| Hill sphere | ~1–3 ly[citation needed] |
| Orbit about Galactic Center | |
| Invariable-to-galactic plane inclination | 60.19° (ecliptic)[citation needed] |
| Distance to Galactic Center | 24,000–28,000 ly [7] |
| Orbital speed | 720,000 km/h (450,000 mi/h)[8] |
| Orbital period | ~230 million years[8] |
The Solar System[b] is the gravitationally bound system of the Sun and the objects that orbit it.[9] It was formed 4.6 billion years ago when a dense region of a molecular cloud collapsed, forming the Sun and a protoplanetary disc. The Sun is an ordinary main sequence star that maintains a balanced equilibrium by the fusion of hydrogen into helium at its core, releasing this energy from its outer photosphere.
The largest objects that orbit the Sun are the eight planets. In order from the Sun, they are four terrestrial planets (Mercury, Venus, Earth and Mars); two gas giants (Jupiter and Saturn); and two ice giants (Uranus and Neptune). All terrestrial planets have solid surfaces. Inversely, all giant planets do not have a definite surface, as they are mainly composed of gases and liquids. Over 99.86% of the Solar System's mass is in the Sun and nearly 90% of the remaining mass is in Jupiter and Saturn.
There is a strong consensus among astronomers[c] that the Solar System has at least eight dwarf planets: Ceres, Pluto, Haumea, Quaoar, Makemake, Gonggong, Eris, and Sedna. There are a vast number of 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).[d] Six planets, six dwarf planets, and other bodies have orbiting natural satellites, which are commonly called 'moons'.
The Solar System is constantly flooded by the Sun's charged particles, the solar wind, forming the heliosphere. Around 75–90 astronomical units, the solar wind is halted, resulting in the heliopause. This is the boundary of the Solar System to interstellar space. The outermost region of the Solar System is the theorized Oort cloud, the source for long-period comets, extending 2,000–200,000 astronomical units (0.032–3.2 light-years). The closest star to the Solar System, Proxima Centauri, is 4.25 light-years away. Both stars belong to the Milky Way galaxy.
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).
- ^ "Our Local Galactic Neighborhood". Interstellar Probe Project. NASA. 2000. Archived from the original on 21 November 2013. Retrieved 8 August 2012.
- ^ Hurt, R. (8 November 2017). "The Milky Way Galaxy". science.nasa.gov. Retrieved 19 April 2024.
- ^ Chiang; Jordan, A. B.; Millis, R. L.; Buie, M. W.; Wasserman, L. H.; Elliot, J. 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.
- ^ C. de la Fuente Marcos & R. de la Fuente Marcos (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.
- ^ Mumma, M. J.; Disanti, M. A.; Dello Russo, N.; Magee-Sauer, K.; Gibb, E.; Novak, R. (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.
- ^ Greicius, Tony (5 May 2015). "NASA Spacecraft Embarks on Historic Journey Into Interstellar Space".
- ^ 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.
- ^ a b "Sun: Facts - NASA Science". science.nasa.gov. Retrieved 19 April 2024.
- ^ "IAU Office of Astronomy for Education". IAU Office of Astronomy for Education. Retrieved 11 December 2023.
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