== 2007 outburst ==

 

During its 2007 return, Holmes unexpectedly brightened from a [[Apparent magnitude|magnitude]] of about 17 to about 2.8 in a period of only 42 hours, making it visible to the naked eye. This represents a change of brightness by a factor of about half a million and is the largest known outburst by a comet. The outburst took place from October 23 to 24, 2007.<ref name=gunn>Gunn, Angela. "[http://blogs.usatoday.com/techspace/2007/10/flash-news-flas.html Flash News Flash!] {{webarchive|url=https://web.archive.org/web/20070625054541/http://blogs.usatoday.com/techspace/2007/10/flash-news-flas.html |date=2007-06-25 }}," ''USA Today'' Tech Space, 24 October 2007. Retrieved 25 October 2007.</ref><ref name=sinnott>{{cite journal|url=http://www.skyandtelescope.com/observing/home/10775326.html |access-date=2007-10-25 |journal=Sky & Telescope |author=Roger W. Sinnott |date=October 24, 2007 |title=Comet Holmes Undergoes Huge Outburst |archive-url=https://archive.today/20071027023929/http://www.skyandtelescope.com/observing/home/10775326.html |archive-date=2007-10-27 |url-status=dead }}</ref> The first person reportedly to notice a change was [[J. A. Henríquez Santana]] on [[Tenerife]] in the [[Canary Islands]]; minutes later, Ramón Naves in [[Barcelona]] noticed the comet at magnitude 7.3.<ref name=sinnott/> It became easily visible to the [[naked eye]] as a bright yellow "star" in [[Perseus (constellation)|Perseus]],<ref name=fischer>Fischer, Daniel. "[http://www.astro.uni-bonn.de/~dfischer/mirror/306.html Incredible comet eruption: from under 17th to 3rd magnitude in hours!]," ''The Cosmic Mirror'', #306, 24 October 2007. Retrieved 25 October 2007.</ref><ref name=map>[http://www.spaceweather.com/images2007/24oct07/skymap_north_holmes.gif?PHPSESSID=u4ckv3guss7diulg57tt3nc281 Skymap: late October 2007], Northeast, after sunset, ''Spaceweather.com''. Retrieved 28 October 2007</ref> and by October 25 17P/Holmes appeared as the third-brightest "star" in that constellation.<ref name=sinnott/>

 

== References ==

{{Reflist}}