Editing Supernova (section)

===Type II===
[[Image:SNIIcurva.svg|thumb|Light curves are used to classify type II-P and type II-L supernovae.<ref name="taxonomy"/><ref name="barbon1979"/>]]
The supernovae of [[Type II supernova|type II]] can also be sub-divided based on their spectra. While most type II supernovae show very broad [[emission line]]s which indicate expansion velocities of many thousands of [[kilometres per second]], some, such as [[SN 2005gl]], have relatively narrow features in their spectra. These are called type IIn, where the "n" stands for "narrow".<ref name="taxonomy"/>

A few supernovae, such as SN 1987K<ref>{{cite journal |last1=Filippenko |first1=A. V. |title=Supernova 1987K: Type II in Youth, Type Ib in Old Age |journal=The Astronomical Journal |date=1988 |volume=96 |page=1941 |doi=10.1086/114940 |bibcode=1988AJ.....96.1941F}}</ref> and [[SN 1993J]], appear to change types: they show lines of hydrogen at early times, but, over a period of weeks to months, become dominated by lines of helium. The term [[Type IIb supernova|"type IIb"]] is used to describe the combination of features normally associated with types II and Ib.<ref name="taxonomy"/>

Type II supernovae with normal spectra dominated by broad hydrogen lines that remain for the life of the decline are classified on the basis of their light curves. The most common type shows a distinctive "plateau" in the light curve shortly after peak brightness where the visual luminosity stays relatively constant for several months before the decline resumes. These are called type II-P referring to the plateau. Less common are type II-L supernovae that lack a distinct plateau. The "L" signifies "linear" although the light curve is not actually a straight line.<ref name="taxonomy"/>

Supernovae that do not fit into the normal classifications are designated peculiar, or "pec".<ref name="taxonomy">
{{cite book
 |last1=Turatto |first1=M.
 |year=2003
 |chapter=Classification of Supernovae
 |title=Supernovae and Gamma-Ray Bursters
 |volume=598 |pages=21–36
 |series=[[Lecture Notes in Physics]]
 |arxiv=astro-ph/0301107
 |citeseerx=10.1.1.256.2965
 |doi=10.1007/3-540-45863-8_3
 |isbn=978-3-540-44053-6
|s2cid=15171296
 }}</ref>