Editing Planet (section)

==== Magnetosphere ====
{{Main|Magnetosphere}}
[[File:Structure_of_the_magnetosphere_LanguageSwitch.svg|lang=en|thumb|[[Earth's magnetic field|Earth's magnetosphere]] (diagram)]]

One important characteristic of the planets is their intrinsic [[magnetic moment]]s, which in turn give rise to magnetospheres. The presence of a magnetic field indicates that the planet is still geologically alive. In other words, magnetized planets have flows of [[electrical conductivity|electrically conducting]] material in their interiors, which generate their magnetic fields. These fields significantly change the interaction of the planet and solar wind. A magnetized planet creates a cavity in the solar wind around itself called the magnetosphere, which the wind cannot penetrate. The magnetosphere can be much larger than the planet itself. In contrast, non-magnetized planets have only small magnetospheres induced by interaction of the [[ionosphere]] with the solar wind, which cannot effectively protect the planet.<ref name="Kivelson2007" />

Of the eight planets in the Solar System, only Venus and Mars lack such a magnetic field.<ref name="Kivelson2007" /> Of the magnetized planets, the magnetic field of Mercury is the weakest and is barely able to deflect the [[solar wind]]. Jupiter's moon [[Ganymede (moon)|Ganymede]] has a magnetic field several times stronger, and Jupiter's is the strongest in the Solar System (so intense in fact that it poses a serious health risk to future crewed missions to all its moons inward of Callisto<ref>{{Cite journal |last1=De Angelis |first1=G. |last2=Clowdsley |first2=M. S. |last3=Nealy |first3=J. E. |last4=Tripathi |first4=R. K. |last5=Wilson |first5=J. W. |display-authors=4 |date=January 2004 |title=Radiation analysis for manned missions to the Jupiter system |url=https://linkinghub.elsevier.com/retrieve/pii/S0273117704003205 |journal=Advances in Space Research |language=en |volume=34 |issue=6 |pages=1395–1403 |doi=10.1016/j.asr.2003.09.061 |pmid=15881781 |bibcode=2004AdSpR..34.1395D |access-date=13 July 2022 |archive-date=25 April 2022 |archive-url=https://web.archive.org/web/20220425152824/https://linkinghub.elsevier.com/retrieve/pii/S0273117704003205 |url-status=live }}</ref>). The magnetic fields of the other giant planets, measured at their surfaces, are roughly similar in strength to that of Earth, but their magnetic moments are significantly larger. The magnetic fields of Uranus and Neptune are strongly tilted relative to the planets' rotational [[Axis of rotation|axes]] and displaced from the planets' centres.<ref name="Kivelson2007">{{cite book |last1=Kivelson |first1=Margaret Galland | last2=Bagenal | first2=Fran |chapter=Planetary Magnetospheres |title=Encyclopedia of the Solar System |date=2007 |publisher=Academic Press |editor=Lucy-Ann McFadden |editor2=Paul Weissman |editor3=Torrence Johnson |isbn=978-0-12-088589-3 |page=[https://archive.org/details/encyclopediaofso0000unse_u6d1/page/519 519] |chapter-url=https://archive.org/details/encyclopediaofso0000unse_u6d1/page/519 }}</ref>

In 2003, a team of astronomers in Hawaii observing the star [[HD 179949]] detected a bright spot on its surface, apparently created by the magnetosphere of an orbiting hot Jupiter.<ref>{{cite web |last=Gefter |first=Amanda |date=17 January 2004 |title=Magnetic planet |url=https://astronomy.com/news-observing/news/2004/01/magnetic%20planet |access-date=29 January 2008 |work=Astronomy |archive-date=1 June 2019 |archive-url=https://web.archive.org/web/20190601224551/http://www.astronomy.com/news-observing/news/2004/01/magnetic%20planet |url-status=dead }}</ref><ref>{{Cite journal |last1=Shkolnik |first1=E. |last2=Walker |first2=G. A. H. |last3=Bohlender |first3=D. A. |date=10 November 2003 |title=Evidence for Planet-induced Chromospheric Activity on HD 179949 |url=https://iopscience.iop.org/article/10.1086/378583 |journal=The Astrophysical Journal |language=en |volume=597 |issue=2 |pages=1092–1096 |doi=10.1086/378583 |bibcode=2003ApJ...597.1092S |s2cid=15829056 |issn=0004-637X |access-date=10 July 2022 |archive-date=10 July 2022 |archive-url=https://web.archive.org/web/20220710171419/https://iopscience.iop.org/article/10.1086/378583 |url-status=live |arxiv=astro-ph/0303557 }}</ref>