Meteor shower
In addition to individually occurring ( sporadic ) meteors, there are meteor streams (also meteor showers or shooting stars , often wrongly also meteorite showers ). They are an accumulation of falling stars at certain times of the year and originate largely from the dust particles of dissolved comets .
The paths of these small bodies run approximately parallel in space and therefore seem to come in perspective from a vanishing point ( radian ) in the sky. Their exact course and the origin of the bodies can be determined if their traces of light from several meteor stations are photographed against the star background .
Formation of meteor swarms
Shooting stars or meteor streams can arise when the earth moves close to a comet's orbit or nearly crosses it on its way around the sun . Comets close to the sun constantly lose part of their mass in the form of gas and dust ( comet tail ), pieces of rock and other small particles called meteoroids . They are distributed over a large part of the comet's orbit over the course of the millennia , which is why a meteor shower usually returns every year at the point where the earth flies through the area of this cloud of matter. The strength of a meteor shower is given as the Zenithal Hourly Rate (ZHR); it is the hourly number of meteors that are visible at their peak under ideal conditions.
Temporal variation of the meteors and their radians
As a rule, most of the falling stars can be seen in the early morning sky in the east - just before dawn - because the observer then “ turns towards them” as a result of the earth's rotation .
All shooting stars a meteor shower seem to come here for the same point in the sky, the radians . The meteor shower is usually named after the constellation in which this radiant is located (e.g. Perseids : constellation Perseus ). However, its celestial coordinates change if a meteor swarm lasts longer than a few days, because the elliptical orbits of the particles around the sun have a curvature that is about 1 ° per day.
The particle density on the comet's trajectory is significantly higher shortly before and after the comet flies past the sun. This event is known as a meteor storm , during which in some years more than a thousand meteors can be seen per hour.
A particularly large number of meteors can also only occur a few years after the comet's perihelion , such as the Leonids in 2002 and the 1998 perihelion of the associated comet Tempel-Tuttle .
Since these particle clouds dissolve over the years and their orbits around the sun can be changed by orbital disturbances and other gravitational or non-gravitational influences, meteor streams disappear in the long term (like the Leonids after 2002), while new streams from current (still "active") ) Comets are formed.
Annually recurring meteor streams
The following table is an excerpt from the list of meteor streams and contains only the strongest of these currents, which can have more than about ten falling stars per hour. The three most important ( Quadrantids , Perseids and Geminids ) are highlighted in bold.
Date (maximum) | Surname | origin | ZHR |
---|---|---|---|
Jan 1st to Jan 5th (Jan 3rd) |
Quadrantiden (Bootiden) |
Asteroid 2003 EH1 |
120 |
Jan 25 to Apr 15 (March 24) |
Virginids | ecliptical | 5 |
Apr 16 to Apr 25 (Apr 22) |
Lyrids | Comet C / 1861 G1 (Thatcher) |
18th |
April 19 to May 28 (May 5) |
May aquariids (η-aquariids) |
Halley's Comet | 60 |
April 15 to July 15 (May 19) |
Sagittarids | ecliptical | 5 |
July 12th to August 25th (August 3rd) |
July aquariids (δ aquariids) |
20th | |
July 17th to August 24th (August 12th) |
Perseids (Laurentius tears) |
Comet 109P / Swift-Tuttle |
110 |
Oct 6th to Oct 10th (Oct 8th) |
Draconids , also Giacobinids |
Comet 21P / Giacobini-Zinner |
var. |
Oct 2 to Nov 7 (Oct 21) |
Orionids | Halley's Comet | 23 |
Oct 1 to Nov 25 ( Nov 5 and 12) |
Taurids | ecliptical | 5 |
Nov 14 to Nov 21 (Nov 17) |
Leonids | Comet 55P / Tempel-Tuttle |
var. |
7th December to 17th December (14th December) |
Geminids |
Asteroid 3200 Phaethon |
120 |
literature
- Cuno Hoffmeister : Meteors, their cosmic and earthly relationships. Akademische Verlagsgesellschaft mbH, Leipzig (1937)
- Cuno Hoffmeister: Meteor Streams . Joh. Ambr. Barth Verlag, Leipzig (1948)
- Fritz Heide: A little meteorite science . Understandable Science Volume 23, Springer-Verlag, Berlin 1957.