{{Short description|Meteor shower}} {{About||the bear family|Ursidae}} {{Infobox meteor shower | name = Ursids (URS) | image = Radiant for Ursids 2018.jpg | caption = Ursa Minor with the radiant of the Ursids marked in red | pronounce = | date = | parent = 8P/Tuttle<ref name="Kronk"/> <!-- Radiant --> | constellation = Ursa Minor (near Kochab) | ra = {{RA|14|36}}<ref name=IMO/> | dec = {{DEC|+75.3}}<ref name=IMO/> (Northern Hemisphere) <!-- Properties --> | month = {{Nowrap|December 17 – December 26}}<ref name="Kronk"/> | peak = December 22<ref name="Kronk"/> | velocity = 33<ref name=IMO>[https://www.imo.net/resources/calendar/#Ursids IMO Meteor Shower Calendar: Ursids (URS)]</ref> | zhr = 10<ref name="Kronk"/> | notes = }}
The '''Ursid''' (URS) meteor activity begins annually around December 17 and runs for over a week, until the 25th or 26th. This meteor shower is named for its radiant point, which is located near the star Beta Ursae Minoris (Kochab) in the constellation Ursa Minor.
== History == The Ursids were probably discovered by William F. Denning, who observed them for several years around the start of the 20th century.<ref name="Kronk"/> While there were sporadic observations after, the first coordinated studies of the shower didn't begin until Dr. A. Bečvář observed an outburst of 169 per hour in 1945.<ref name="Kronk"/> Further observations in the 1970s and ongoing to current have established a relationship with comet 8P/Tuttle.<ref name="Kronk"/> Peter Jenniskens and Esko Lyytinen discovered that outbursts could happen when comet Tuttle was at aphelion because some meteoroids get trapped in the 7/6 orbital resonance with Jupiter.
== Technical information== Earlier observations described an average radiant of RA={{DEC|217}}, DEC={{DEC|76}},<ref name="Kronk"/> with maximum occurring at a solar longitude of 270.66 deg (about December 22), with the duration being established as December 17–24.
The Ursids have a particularly narrow stream, prompting veteran meteor observer, Norman W. McLeod, III (Florida) to comment that the Ursids "must be a compact stream like the Quadrantids. You have to be within 12 hours of maximum to see much."<ref name="Kronk"/>
== References == <references>
<!-- unused <ref name=moore_rees2011>{{citation | first1=Patrick | last1=Moore | first2=Robin | last2=Rees | title=Patrick Moore's Data Book of Astronomy | edition=2nd | publisher=Cambridge University Press | date=2011 | isbn=978-0-521-89935-2 | page=275 | url=https://books.google.com/books?id=2FNfjWKBZx8C&pg=PA275}}</ref> -->
<ref name="Kronk">{{cite web |title=Observing the Ursids |publisher=Meteor Showers Online |author=Gary W. Kronk |author-link=Gary W. Kronk |url=http://meteorshowersonline.com/showers/ursids.html |archive-url=https://web.archive.org/web/20130724160438/http://meteorshowersonline.com/showers/ursids.html |archive-date=2013-07-24 |url-status=dead |access-date=2012-11-17}}</ref>
</references>
== External links == * [http://meteorshowersonline.com/showers/ursids.html Gary Kronk's Meteor Showers Online - Ursids] * [https://web.archive.org/web/20051219053932/http://www.imo.net/calendar/2005/fall International Meteor Organisation Calendar - Fall 2005] * [http://ursid.seti.org NASA Ursid Airborne Campaign] (2008 + Java applet) * [http://www5f.biglobe.ne.jp/~hro/Flash/2011/URS/ 2011 Ursids Radio results] (RMOB) * [http://www.constellation-guide.com/ursids/ Ursids at Constellation Guide]
{{Meteor showers}}
Category:Meteor showers Category:December