Meteor Shower

The light phenomena produced by particles (meteoroids) traveling through a planet’s atmosphere and heating the surrounding air.   Meteor showers occur at particular times of year when the Earth intersects  debris traveling along the orbit of a comet.

Light phenomenon that occurs when the orbit of the Earth passes through a meteor stream. For example, the Earth’s orbit intersects the orbit of the comet Tempel-Tuttle every November, producing the Leonid meteor shower. All the meteoroids in the stream basically travel parallel to each other and when they hit Earth’s atmosphere appear to originate from a single point (the radiant). The meteors appear to come from a specific constellation (the constellation Leo in the case of Tempel-Tuttle).

The duration of a shower depends on how long it takes for Earth to pass through the meteor stream. It is measured by calculating the number of meteors that a single visual observer would see in an hour assuming a limiting magnitude of 6.5 and the radiant at the zenith. This is known as the zenithal hourly rate (ZHR) and is a measure of the concentration of material in the stream. The ZHR changes from year to year as the meteor stream constantly evolves. For example, if the comet has recently visited the inner Solar System, there generally will be more meteoroids in the stream and a higher ZHR results. Extremely active showers with ZHR >1000 are usually called ‘meteor storms’.

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