Editing Planetary system (section)

====Mutual inclination====
The mutual [[Exoplanetology#Inclination vs. spin–orbit angle|inclination]] between two planets is the angle between their [[orbital plane]]s. Many compact systems with multiple close-in planets interior to the equivalent orbit of [[Venus]] are expected to have very low mutual inclinations, so the system (at least the close-in part) would be even flatter than the Solar System. Captured planets could be captured into any arbitrary angle to the rest of the system. {{As of|2016}} there are only a few systems where mutual inclinations have actually been measured<ref>{{cite journal | arxiv=1606.04485 | doi=10.3847/1538-3881/153/1/45 | title=Kepler-108: A Mutually Inclined Giant Planet System | year=2017 | last1=Mills | first1=Sean M. | last2=Fabrycky | first2=Daniel C. | journal=The Astronomical Journal | volume=153 | issue=1 | page=45 | bibcode=2017AJ....153...45M | s2cid=119295498 | doi-access=free }}</ref> One example is the [[Upsilon Andromedae]] system: the planets c and d have a mutual inclination of about 30 degrees.<ref>{{cite journal | arxiv=1411.1059 | doi=10.1088/0004-637X/798/1/46 | title=The 3-dimensional architecture of the Upsilon Andromedae planetary system | year=2014 | last1=Deitrick | first1=Russell | last2=Barnes | first2=Rory | last3=McArthur | first3=Barbara | last4=Quinn | first4=Thomas R. | last5=Luger | first5=Rodrigo | last6=Antonsen | first6=Adrienne | last7=Fritz Benedict | first7=G. | journal=The Astrophysical Journal | volume=798 | page=46 | s2cid=118409453 }}</ref><ref>{{cite web|url=http://www.nasa.gov/mission_pages/hubble/science/outofwack.html |title=NASA – Out of Whack Planetary System Offers Clues to a Disturbed Past |publisher=Nasa.gov |date=2010-05-25 |access-date=2012-08-17}}</ref>