Editing Solar System (section)

===Future of the Solar System===
[[File:Sun red giant.svg|thumb|The current Sun compared to its peak size in the red-giant phase]]
The future of the Solar System depends a lot on what happens to the [[Sun]], since it is the [[star]] at the center and controls everything with its [[gravity]] and [[energy]]. Right now, the Sun is in the main part of its life, called the main sequence. During this time, it is turning [[hydrogen]] into [[helium]] through a process called [[nuclear fusion]], which creates the [[light]] and [[heat]] [[Earth]] gets. But this would not last forever. In about 5 billion years, the Sun will start to run out of hydrogen fuel. When that happens, the core will shrink, and the outer layers will puff up, making the Sun grow much bigger. This next stage is called the red giant phase. As a [[red giant]], the Sun will become so large that it might swallow up [[Mercury (planet)|Mercury]] and [[Venus]], and it could even reach [[Earth]], depending on how much it expands.<ref name=":13">{{Cite journal|last1=SchrÃ¶der|first1=K.-P.|last2=Connon Smith|first2=Robert|date=2008-05-01|title=Distant future of the Sun and Earth revisited|journal=Monthly Notices of the Royal Astronomical Society|language=en|volume=386|issue=1|pages=155–163|doi=10.1111/j.1365-2966.2008.13022.x |doi-access=free }}</ref>

When the Sun becomes a red giant, it will also start to lose a lot of its [[mass]]. This happens because strong [[solar wind]]s will blow material off the Sun and into space. As the Sun gets lighter, its gravity will weaken, and the planets that survive will slowly move into wider [[orbit]]s. Even if Earth is not swallowed by the Sun, it will still be in big trouble. The intense [[heat]] and [[radiation]] will likely destroy [[Atmosphere of Earth|Earth's atmosphere]] and [[ocean]]s, making it impossible for [[life]] to survive. Earth will become dry and lifeless. The inner Solar System will turn into a very dangerous and hostile place. The outer planets, like [[Jupiter]], [[Saturn]], [[Uranus]], and [[Neptune]], will probably survive, but their [[Natural satellite|moon]]s and [[Ring system|ring]]s might change.<ref name=":14">{{Cite web|date=2018-12-11|title=Chapter 6: Aging Into Gianthood - NASA Science|url=https://science.nasa.gov/exoplanets/resources/life-and-death/chapter-6/|access-date=2025-07-07|language=en-US}}</ref> At some point, the core of the Sun will get hot enough to start burning helium. This process is called [[Triple-alpha process|helium fusion]]. However, the Sun will only be able to burn helium for a short time compared to how long it burned hydrogen. The Sun is not big enough or heavy enough to fuse heavier elements like [[carbon]] or [[oxygen]]. So after the helium runs out, the [[nuclear reaction]]s in the core will stop. Without these reactions, the Sun would not be able to hold up its outer layers.<ref name=":14" />

After the Sun finishes its red giant phase, it will shed its outer layers and leave behind a small but very hot core called a white dwarf. A [[white dwarf]] is about the size of Earth, but it still holds about half the mass of the original Sun. Even though it would not make energy anymore, it will still be very hot and dense.<ref name=":13" /> When the Sun's outer layers float away into space, they might create a cloud of glowing gas called a [[planetary nebula]]. This is a bright shell of gas that shines in space for a short time. These outer layers are made of material that once belonged to the Sun, but now they contain heavier elements like [[carbon]] that were made inside the Sun over its lifetime. This gas will go back into the [[interstellar medium]], the space between stars, where it can help form new [[star]]s and [[planet]]s one day.<ref>{{Cite web|title=Planetary Nebulas {{!}} Center for Astrophysics {{!}} Harvard & Smithsonian|url=https://www.cfa.harvard.edu/research/topic/planetary-nebulas|access-date=2025-07-07|website=www.cfa.harvard.edu}}</ref><ref>{{Cite journal|last1=Gesicki|first1=K.|last2=Zijlstra|first2=A. A.|last3=Miller Bertolami|first3=M. M.|date=2018-05-07|title=The mysterious age invariance of the planetary nebula luminosity function bright cut-off|url=https://www.nature.com/articles/s41550-018-0453-9|journal=Nature Astronomy|language=en|volume=2|issue=7|pages=580–584|doi=10.1038/s41550-018-0453-9|hdl=11336/82487 |issn=2397-3366}}</ref>

Over time, the white dwarf will cool down slowly, taking trillions of years to lose its [[heat]]. It would not shine like the Sun does now, but it will still have gravity strong enough to keep the [[outer planet]]s and moons orbiting around it. However, over a very long time, the orbits of those planets might change slightly because there will be less [[gravity]] and other [[force]]s acting on them. Over an even longer period of time, tens or even hundreds of billions of years, the Solar System may start to break apart. Tiny changes, like the pull from passing [[star]]s or forces from the [[galaxy]], can slowly change the orbits of [[planet]]s and other space objects. Some planets or moons might get knocked out of the Solar System and drift off into deep space, becoming free-floating objects. Others might spiral inward and crash into the [[white dwarf]] that used to be the [[Sun]]. Eventually, the Solar System could completely fall apart, with its planets and moons scattered across the galaxy. This slow breakup is a natural part of how gravity works over a long time, and it would be the end of the Solar System.<ref>{{Cite journal|last=Dyson|first=Freeman J.|date=1979-07-01|title=Time without end: Physics and biology in an open universe|url=https://link.aps.org/doi/10.1103/RevModPhys.51.447|journal=Reviews of Modern Physics|language=en|volume=51|issue=3|pages=447–460|doi=10.1103/RevModPhys.51.447|issn=0034-6861}}</ref>