Editing Solar System (section)

===The Present-day Conditions of the Solar System===
[[File:Solar System graphic by NASA (wide).png|thumb|The Solar System]]
At the very center of the Solar System is the [[Sun]], which is a middle-aged [[star]] called a [[G-type main-sequence star]]. The Sun is very massive, it holds more than 99.8% of all the [[mass]] in the Solar System. The Sun gives off [[light]] and [[heat]], which make [[life]] on [[Earth]] possible. It also creates the [[gravity]] that keeps all the [[planet]]s, [[Natural satellite|moon]]s, [[asteroid]]s, and [[comet]]s moving in their [[orbit]]s.<ref name=":10" /> Even though the Sun looks calm in the sky, it is actually very active. It gives off [[radiation]] and sends out a stream of charged particles called the [[solar wind]].<ref name=":11" /> This wind stretches far out into space and helps create the edge of a giant bubble called the [[heliosphere]], which surrounds the entire Solar System.<ref name=":7" />

Surrounding the Sun are the eight major planets, which are split into two main groups. The first group is the terrestrial planets, [[Mercury (planet)|Mercury]], [[Venus]], [[Earth]], and [[Mars]]. These are small, [[Terrestrial planet|rocky planet]]s made mostly of [[rock]] and [[metal]].<ref name=":1" /> The second group includes the [[Gas giant|gas]] and [[ice giant]]s, [[Jupiter]], [[Saturn]], [[Uranus]], and [[Neptune]]. These planets are much bigger and made mostly of gases like [[hydrogen]] and [[helium]], and ices such as [[water]], [[ammonia]], and [[methane]].<ref name=":2" /><ref name=":3" /> All the planets move in oval-shaped orbits (called [[elliptical orbit]]s) around the Sun, and they mostly stay in the same flat area called the [[Ecliptic|ecliptic plane]].<ref name=":4" /><ref name=":5" /> Most of them spin in the same direction as the Sun, but there are a couple of exceptions. Venus spins backward, and Uranus spins on its side.<ref>{{Cite web|last=Franzen|first=Harald|title=Why Venus Spins the Wrong Way|url=https://www.scientificamerican.com/article/why-venus-spins-the-wrong/|access-date=2025-07-05|website=Scientific American|language=en}}</ref><ref>{{Cite web|date=2017-11-10|title=Uranus: Facts - NASA Science|url=https://science.nasa.gov/uranus/facts/|access-date=2025-07-05|language=en-US}}</ref> Besides the planets, the Solar System also has lots of smaller objects. Between Mars and Jupiter is the [[asteroid belt]], which contains millions of space rocks. Some as small as dust, and others as big as the [[dwarf planet]] [[Ceres]].<ref name=":19">{{Cite web|date=2025-05-14|title=Asteroid Belt: what is it and how did it form?|url=https://www.skyatnightmagazine.com/space-science/asteroid-belt-facts-formation|access-date=2025-07-05|website=BBC Sky at Night Magazine|language=en}}</ref> Even farther out is the Kuiper Belt, which is full of icy objects like [[Pluto]], [[Haumea (dwarf planet)|Haumea]], and [[Makemake (dwarf planet)|Makemake]]. These are called [[Trans-Neptunian object|trans-Neptunian objects (TNOs)]], and they are leftovers from the Solar System's early days. They never became [[planet]]s because the gravity from the big planets, like Jupiter, kept pulling things around and disturbing them.<ref>{{Cite web|title=Trans-Neptunian object {{!}} EBSCO Research Starters|url=https://www.ebsco.com/research-starters/astronomy-and-astrophysics/trans-neptunian-object|access-date=2025-07-05|website=www.ebsco.com|language=en}}</ref> Way beyond that, scientists think there is something called the [[Oort cloud|Oort Cloud]]. It is a giant, round shell of icy objects that surrounds the Solar System. Scientists have not seen it directly, but they think it is there because it is likely the home of long-period comets. The ones that take hundreds or thousands of years to orbit the Sun. The Oort Cloud is believed to be the very edge of the Sun’s gravitational reach.<ref name=":6" />

The Solar System is always changing. It is not just made of planets and moons, there are lots of smaller objects moving around too, like [[comet]]s, [[meteoroid]]s, and [[Centaur (planetoid)|centaur]]s. Centaurs are unusual because they have features of both asteroids and comets.<ref name=":12">{{Cite web|last=Metcalfe|first=Tom|date=2021-10-07|title=Our solar system's centaurs are half-asteroid, half-comet|url=https://www.astronomy.com/science/our-solar-systems-centaurs-are-half-asteroid-half-comet/|access-date=2025-07-05|website=Astronomy Magazine|language=en-US}}</ref> Sometimes, comets from faraway places like the Kuiper Belt or the Oort Cloud travel into the inner part of the Solar System. As they get closer to the Sun, the heat causes their ice to melt, creating bright tails of gas and dust. These tails can be really beautiful and are often visible from [[Earth]].<ref name=":8" /> [[Meteoroid]]s are small rocks that sometimes enter Earth’s atmosphere. When they burn up in the sky, we see them as [[meteor]]s or "shooting stars." If a bigger piece makes it all the way to the ground, it is called a [[meteorite]].<ref name=":9" /> While big impacts are rare, scientists still keep an eye on [[Near-Earth object|near-Earth objects (NEOs)]] just in case.<ref>{{Cite web|title=Near-Earth Object Program - NASA|url=https://www.nasa.gov/stem-content/near-earth-object-program/|access-date=2025-07-05|language=en-US}}</ref> Centaurs are icy objects with unstable orbits between Jupiter and Neptune.<ref name=":12" /> They might one day become short-period comets that visit the inner Solar System more often.<ref>{{Citation|last1=Peixinho|first1=Nuno|title=Chapter 14 - From Centaurs to comets: 40 Years|date=2020-01-01|url=https://www.sciencedirect.com/science/article/pii/B978012816490700014X|work=The Trans-Neptunian Solar System|pages=307–329|editor-last=Prialnik|editor-first=Dina|publisher=Elsevier|doi=10.1016/b978-0-12-816490-7.00014-x|isbn=978-0-12-816490-7|access-date=2025-07-05|last2=Thirouin|first2=Audrey|last3=Tegler|first3=Stephen C.|last4=Di Sisto|first4=Romina P.|last5=Delsanti|first5=Audrey|last6=Guilbert-Lepoutre|first6=Aurélie|last7=Bauer|first7=James G.|arxiv=1905.08892 |editor2-last=Barucci|editor2-first=M. Antonietta|editor3-last=Young|editor3-first=Leslie A.}}</ref> In recent years, astronomers even discovered objects from outside our Solar System, like ‘[[Oumuamua]] and Comet [[2I/Borisov]]. These interstellar visitors came from far beyond the Sun’s reach, giving us clues about how other star systems might form.<ref>{{Cite web|date=2017-11-29|title='Oumuamua - NASA Science|url=https://science.nasa.gov/solar-system/comets/oumuamua/|access-date=2025-07-05|language=en-US}}</ref><ref>{{Cite web|date=2020-04-17|title=Comet 2I/Borisov - NASA Science|url=https://science.nasa.gov/solar-system/comets/2i-borisov/|access-date=2025-07-05|language=en-US}}</ref>

There are over 800 known [[Natural satellite|moon]]s in our Solar System, and they come in all shapes and sizes.<ref>{{Cite web|date=2023-05-31|title=Moons|url=https://science.nasa.gov/solar-system/moons/|access-date=2025-07-05|language=en-US}}</ref> Some moons are fiery and active, like [[Io (moon)|Io]], which has [[volcano]]es constantly erupting.<ref>{{Cite web|date=2017-11-17|title=Io|url=https://science.nasa.gov/jupiter/jupiter-moons/io/|access-date=2025-07-05|language=en-US}}</ref> Others, like [[Europa (moon)|Europa]] and [[Enceladus (moon)|Enceladus]], are covered in ice but may have liquid [[ocean]]s hidden underneath.<ref>{{Cite web|last=US Department of Commerce|first=National Oceanic and Atmospheric Administration|title=Are there oceans on other planets?|url=https://oceanservice.noaa.gov/facts/et-oceans.html|access-date=2025-07-05|website=oceanservice.noaa.gov|language=EN-US}}</ref> These icy moons are interesting because they might even have the right conditions for [[life]].<ref>{{Cite web|last=Barbuzano|first=Javier|date=2023-08-14|title=Subsurface Oceans Could Boost Exoplanet Habitability|url=https://eos.org/articles/subsurface-oceans-could-boost-exoplanet-habitability|access-date=2025-07-05|website=Eos|language=en-US}}</ref> Some planets, like Saturn and Neptune, have lots of moons, creating huge moon systems that scientists are still exploring and learning about.<ref>{{Cite web|date=2025-03-17|title=Which planet has the most moons?|url=https://www.skyatnightmagazine.com/space-science/which-planet-has-most-moons|access-date=2025-07-05|website=BBC Sky at Night Magazine|language=en}}</ref> Besides natural moons, the Solar System also has many [[spacecraft]] and [[Satellite (artificial)|satellite]]s that humans have sent into space to learn more about our Solar System. Some of these orbit Earth, while others go much farther.<ref>{{Cite web|date=2025-06-18|title=Space exploration - Solar System, Probes, Missions {{!}} Britannica|url=https://www.britannica.com/science/space-exploration/Solar-system-exploration|access-date=2025-07-05|website=www.britannica.com|language=en}}</ref> For example, [[Voyager 1]] has traveled so far that it has entered interstellar space, beyond the edge of the Solar System.<ref>{{Cite web|date=2024-03-10|title=Where Are Voyager 1 and 2 Now? - NASA Science|url=https://science.nasa.gov/mission/voyager/where-are-voyager-1-and-voyager-2-now/|access-date=2025-07-05|language=en-US}}</ref> Other missions like [[Juno (spacecraft)|Juno]] (orbiting Jupiter), [[Perseverance (rover)|Perseverance]] (exploring Mars), the [[James Webb Space Telescope]], and [[New Horizons]] (which flew past Pluto) are helping us study planets, moons, and stars in detail.<ref>{{Cite web|date=2023-06-15|title=Juno - NASA Science|url=https://science.nasa.gov/mission/juno/|access-date=2025-07-05|language=en-US}}</ref><ref>{{Cite web|date=2017-12-05|title=Mars 2020: Perseverance Rover - NASA Science|url=https://science.nasa.gov/mission/mars-2020-perseverance/|access-date=2025-07-05|language=en-US}}</ref><ref>{{Cite web|title=Mission Timeline|url=https://webbtelescope.org/home/news/milestones/mission-timeline|access-date=2025-07-05|website=Webb|language=en}}</ref><ref>{{Cite web|date=2017-12-05|title=New Horizons|url=https://science.nasa.gov/mission/new-horizons/|access-date=2025-07-05|language=en-US}}</ref>

Over billions of years, the planets in our Solar System have settled into stable orbits. This means that even though their paths can slowly change, they mostly stay the same over time. These changes happen very slowly and are caused by [[gravity]] pulling on the planets from other planets and the [[Sun]]. The way the planets are arranged now is called the [[Epoch (astronomy)|current epoch]], and it is expected to stay stable for billions more years. The [[orbit]]s might change a little in shape or tilt, but not in a way that causes big problems. This stability is really important because it means we can predict how [[planet]]s move far into the future. It also helps keep [[Earth]] safe and habitable, making [[life]] possible for a long time.<ref>{{Citation|last=Laskar|first=Jacques|title=Solar system: Stability|date=1997|url=https://link.springer.com/rwe/10.1007/1-4020-4520-4_382|encyclopedia=Encyclopedia of Planetary Science|series=Encyclopedia of Earth Science |pages=762–766|publisher=Springer, Dordrecht|language=en|doi=10.1007/1-4020-4520-4_382|isbn=978-1-4020-4520-2|access-date=2025-07-05}}</ref>