Popular Astronomy

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Amazing but True

Here are some surprising facts about meteors (shooting stars) and fireballs:

  • meteors take their name from meteorology - the study of the weather. This name arose because until a couple of centuries ago the prevailing scientific view was that meteors were purely atmospheric phenomena ... and nothing to do with anything entering the Earth's atmosphere from space. They were wrong !
  • most naked eye meteors are produce by tiny particles - comparable in size with a grain or sand or a coffee granule
  • the reason that such small particles can produce flashes of light visible from the Earth's surface is because they "hit" the Earth's atmosphere at very high speed - tens of kilometres per second. Even the slowest meteors arrive at speeds of 10-20 kilometres per second!
  • fireballs are merely very bright meteors, produce from larger objects - the size of a marble upwards
  • The Chelyabinsk fireball, visible over Russia in February 2013, is believed to have been produced from an object originally around 17 metres across
  • Scientists are rather unsure as to how much meteor related material encounters the Earth each day. Estimates range from 5 tonnes to 300 tonnes.
  • Despite the uncertainty in the amount of meteoric material arriving each day, it is still tiny compared with the mass of the Earth. The extra mass has negligible effect on the Earth's gravity - you can't blame it for any weight that you put on!
  • The meteors that we see are near the top of the Earth's atmosphere - at altitudes of around 80-100 kilometres
  • Because they appear so high up in the Earth's atmosphere the brighter meteors and fireballs can be seen by people located hundreds of kilometres apart and although it may appear is if a fireball is "landing" behind a nearby hill, it will actually be hundreds of kilometres away.
  • Only the largest objects produce a remnant that survives all the way down to the Earth's surface - the remnant which lands is known as a meteorite.
  • Recently fallen meteorites are at best "warm". Although their surface will have been heated to very high temperatures while at high altitude, this heat doesn't penetrate far internally and, after the outer layers have been burnt off, the remaining remnant free-falls to the Earth's surface.
  • Most fireballs visible from the UK will have trajectories that end over the sea ... and so any meteorites from them will end with a "splash".
  • No meteorite has been recovered in the UK since 1991. Most that have "landed" will be hidden by vegetation and nearly all rocks that people find and assume to be meteorites are merely terrestrial rocks or the by-products of iron smelting.
  • The best places in the world to discover meteorites are in Antarctica or in deserts - because these locations are vegetation-free and meteorites on the surface will stand out from the surrounding ice/land.