The Ursid (URS) meteor activity begins annually around December 17 and runs for over a week, until the 25th or 26th. This

meteor shower A meteor shower is a celestial event in which a number of meteors are observed to radiate, or originate, from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth's atmosphere at extre ...

is named for its radiant point, which is located near the star

Beta Ursae Minoris Beta Ursae Minoris (β Ursae Minoris, abbreviated β UMi, Beta UMi), formally named Kochab , is the brightest star in the bowl of the Little Dipper asterism (which is part of the constellation of Ursa Minor), and only slightly fainter tha ...

(Kochab) in the constellation

Ursa Minor Ursa Minor (Latin: 'Lesser Bear', contrasting with Ursa Major), also known as the Little Bear, is a constellation located in the far northern sky. As with the Great Bear, the tail of the Little Bear may also be seen as the handle of a ladle, h ...

History

The Ursids were probably discovered by William F. Denning, who observed them for several years around the start of the 20th century. 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. Further observations in the 1970s and ongoing to current have established a relationship with

comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ar ...

8P/Tuttle 8P/Tuttle (also known as Tuttle's Comet or Comet Tuttle) is a periodic comet with a 13.6-year orbit. It fits the classical definition of a Jupiter-family comet with an orbital period of less than 20 years, but does not fit the modern definitio ...

. 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 In celestial mechanics, orbital resonance occurs when orbiting bodies exert regular, periodic gravitational influence on each other, usually because their orbital periods are related by a ratio of small integers. Most commonly, this relationsh ...

with

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but ...

Technical information

Earlier observations described an average radiant of RA=217 deg, DEC=+76 deg, 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 The Quadrantids (QUA) are a meteor shower that peaks in early January and whose radiant lies in the constellation Boötes. The zenithal hourly rate (ZHR) of this shower can be as high as that of two other reliably rich meteor showers, the Persei ...

. You have to be within 12 hours of maximum to see much."

References

External links

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
{{Meteor showers Meteor showers December events