Ursids

from Wikipedia, the free encyclopedia
Meteor
shower Ursiden
activity
Beginning December 17th
maximum December 22
The End December 26th
Radian position
RA 14280014 h 28 m
DE + 76 °
ZHR 10
Population index 2.8
geocentric
speed 		33 km / s

The Ursids are a meteor shower that can be observed in the last decade of December. The mother body of this meteor shower is comet 8P / Tuttle . Its radiant lies in the constellation Ursa Minor near the star Kochab . The radian is thus circumpolar . The Ursiden have a maximum ZHR of 10 meteors per hour. However, significantly higher numbers were observed in isolated cases.

history

The Ursids were discovered by William F. Denning around 1900 , but received little attention for a long time. On December 22, 1945, Czech astronomers accidentally observed a powerful eruption of the meteor shower, with a ZHR of over 100 being reached. In the years that followed, the Ursids were systematically examined, but the meteor numbers observed were always very low compared to 1945. Therefore, interest in this meteor shower soon waned again. It was not until the early 1970s that British amateur astronomers carried out further investigations , with very low ZHR being found. However, radio observations revealed a brief outbreak with a ZHR of about 30 in the daytime of December 22, 1973. The Ursids made a similarly strong appearance on December 22, 1979, this time it was Norwegian observers who were able to see the meteors in the night sky . In several European countries a significantly stronger outbreak of the ursides, with ZHR up to 100, was observed on December 22, 1986.

It has long been known that 8P / Tuttle is the comet of origin of the Ursids. The orbital period of this tail star is 13.5 years. Interestingly, the Ursid eruptions observed in 1945, 1973 and 1986 did not coincide with the proximity of the sun, but with the distance of the comet. Peter Jenniskens and Esko Lyytinen developed a model that demonstrates this unusual phenomenon. a. explained by the force of gravity of the planet Jupiter . The same authors predicted another Ursid eruption for December 22nd, 2000 - again the comet was far from the sun. Numerous observers lay in wait, but the results were inconsistent. Video recordings and radio echoes in particular indicated increased meteor activity, but doubts remained about the methodology used. In addition, visual observers only registered the usual low ursid rates.

Similar influences and orbital disturbances by Jupiter occur not only with the comets of the Jupiter family , but also with other meteor streams such as the Draconids and the Quadrantids .

Web links

Individual evidence

  1. ↑ IMO Meteor Shower Calendar 2019 , accessed June 19, 2019