Editing Orion Nebula (section)

===Stellar wind and effects===
Once formed, the stars within the nebula emit a stream of charged particles known as a [[stellar wind]]. [[OB star|Massive stars]] and [[T Tauri star|young stars]] have much stronger stellar winds than the [[Sun]].<ref>Ker Than, January 11, 2006, "[http://www.space.com/scienceastronomy/060111_orion_news.html The Splendor of Orion: A Star Factory Unveiled]", Space.com</ref> The wind forms shock waves or hydrodynamical instabilities when it encounters the gas in the nebula, which then shapes the gas clouds. The shock waves from stellar wind also play a large part in stellar formation by compacting the gas clouds, creating density inhomogeneities that lead to gravitational collapse of the cloud.

[[File:Ripples.png|thumb| View of the ripples ([[Kelvin–Helmholtz instability]]) formed by the action of stellar winds on the cloud.]]

There are three different kinds of shocks in the Orion Nebula. Many are featured in [[Herbig–Haro objects]]:<ref>"[http://www.vanderbilt.edu/news/releases?id=23966 Mapping Orion's Winds]", January 16, 2006, ''Vanderbilt News Service''</ref>
* [[Bow shock]]s are stationary and are formed when two particle streams collide with each other. They are present near the hottest stars in the nebula where the stellar wind speed is estimated to be thousands of kilometers per second and in the outer parts of the nebula where the speeds are tens of kilometers per second. Bow shocks can also form at the front end of stellar jets when the jet hits [[interstellar medium|interstellar particles]].
* Jet-driven shocks are formed from jets of material sprouting off newborn [[T Tauri stars]]. These narrow streams are traveling at hundreds of kilometers per second and become shocks when they encounter relatively stationary gases.
* Warped shocks appear bow-like to an observer. They are produced when a jet-driven shock encounters gas moving in a cross-current.
* The interaction of the stellar wind with the surrounding cloud also forms "waves" which are believed to be due to the hydrodynamical [[Kelvin-Helmholtz instability]].<ref>Denise Chow. [https://web.archive.org/web/20130626131145/http://www.nbcnews.com/id/38757647 Young stars blamed for space cloud ripples], ''[[NBC News]]''</ref>

The dynamic gas motions in M42 are complex, but are trending out through the opening in the bay and toward the Earth.<ref name=Balick/> The large neutral area behind the ionized region is currently contracting under its own gravity.

There are also [[supersonic]] 'bullets' of gas piercing the hydrogen clouds of the Orion Nebula. Each bullet is ten times the diameter of [[Pluto]]'s orbit and tipped with iron atoms glowing in the infrared. They were probably formed one thousand years earlier from an unknown violent event.<ref>{{cite web |url=http://www.gemini.edu/index.php?q=node/226 |title=Gemini's Laser Vision Reveals Striking New Details in Orion Nebula |date=March 22, 2007 |work=Gemini Observatory |access-date=June 1, 2010}}</ref>