Just why would anyone want to observe meteors ?
Apart from the fact that they are one of the few astronomical phenomena that play out in real time, sometimes a faint streak, sometimes a brilliant fireball breaking up as it enters the atmosphere and leaving a trail that can be observed being disrupted by winds at the top of the atmosphere.
Apart also from the fact that many meteoroids (that's meteors before they enter the earth's atmosphere) are samples from the very earliest days of the solar system. Or else they are fragments of solar system bodies that were flung into space by colossal impacts.
Indeed, the end game for many meteor watchers is to recover fragments of meteoroids that have survived passage through the atmosphere to land as meteorites. The maths for these “dark flight” calculations is tough, but it does yield results. So, very very occasionally it is possible to calculate the orbit of a meteoroid (which tells you where it has come from) and then professionals can examine the chemical composition of the meteorite in a laboratory to determine the exact conditions that existed when it was formed.
Meteorite compositions have been matched with specimens that were returned by the Apollo astronauts, others have exactly the same isotopic ratios as samples analysed by rovers on Mars. Stony meteorites contain “chondrules” that are condensates from the accretion disk of the early solar system. Iron meteorites are the remains of substantial planetesimals that grew big enough for the pressure to melt them, allowing the heavy iron and nickel to sink to their core, before they were destroyed or disrupted in a collision with another solar system body.
The vast majority of meteors are caused by meteoroids no larger than a grain of sand, so no remnant reaches the earth's surface – but it is still possible, using spectral analysis, to determine their composition.
Key to all this subsequent analysis is knowing the distribution of meteoroids throughout the solar system, and we do this by calculating orbits from observations of the meteors.
Clanfield Observatory has three video cameras permanently pointing skywards, recording anything that enters their field of view, during the hours of darkness. They capture anything that moves, be it an aeroplane, a bird, a satellite, a fast moving cloud, and even lightning flashes. Amongst all those “false clips” are meteors. Around 1,500 per year. We use specialist software to analyse them and to match them with observations by other cameras at other observatories around the UK and sometimes Europe. Whenever two cameras observe the same meteor we are able to determine its path in three dimensions. And from that we can determine an orbit for the meteoroid that caused it.
We also capture RADAR “images” of meteors using a receiver installed in the observatory loft! What we actually capture are reflections off the ionised meteor trail of signals which come from a transmitter in southern France. The beauty of this method is that it also works during daytime hours. These traces can last for many seconds and sometimes reveal the breakup of brighter meteoroids into several distinct fragments.
Many meteors arrive in showers at the same time and from the same direction each year. These showers may have durations of a few hours or a few weeks and they may vary slightly by year. Years of observations have noted these concentrations and indeed many have been recognised as having orbits very similar to known solar system bodies, in particular comets. It turns out that as they travel into the inner solar system, comets lay down trails of ice and dust and it is when the earth passes through these trails that we get these meteor showers.
So, accurate observations (our computers are linked to atomic clocks) can determine if there are any variations, perhaps a new filament stream laid down by a subsequent orbit of the comet. Sophisticated analysis can search out new streams from as yet undetermined origins.
Some of this analysis we do at Clanfield, and some is done by professionals with whom we share our observations.
Meteor watches can be fun social events. Accurate meteor observations can increase our understanding of the solar system.