Ursids

Ursids (URS)
Ursa Minor with the radiant of the Ursids marked in red
Parent body	8P/Tuttle[1]
Radiant
Constellation	Ursa Minor (near Kochab)
Right ascension	14h 36m [2]
Declination	+75.3°[2] (Northern Hemisphere)
Properties
Occurs during	December 17 – December 26[1]
Date of peak	December 22[1]
Velocity	33[2] km/s
Zenithal hourly rate	10[1]
See also: List of meteor showers

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[edit]

The Ursids were probably discovered by William F. Denning, who observed them for several years around the start of the 20th century.^[1] 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.^[1] Further observations in the 1970s and ongoing to current have established a relationship with comet 8P/Tuttle.^[1] 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[edit]

Earlier observations described an average radiant of RA=217°, DEC=76°,^[1] 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."^[1]

References[edit]

External links[edit]

• Gary Kronk's Meteor Showers Online - Ursids
• International Meteor Organisation Calendar - Fall 2005
• NASA Ursid Airborne Campaign (2008 + Java applet)
• 2011 Ursids Radio results (RMOB)
• Ursids at Constellation Guide