Perseid Meteor Shower
Created | Updated Jan 28, 2002
The Perseids meteor shower occurs every year form the 23rd of July to the 20th of August and peaks on the 12th usually reaching about 75 ZHR.1 Being a fairly constant meteor shower (i.e. ZHR rarely changes from year to year) and one of the largest make it a popular one to observe, it is also spread over a long period for a great amount of viewing. The meteor shower is a result of the Earth passing through the path that the comet Swift-Tuttle3 and the name of the shower comes from the region of the sky in which the radiant occurs, in this case the constellation of Perseus.
Comets, Meteors and Meteorites
What is the difference between them? This is a common point of confusion and they are frequently mixed up. Well here it is:
- Comets: these are lumps of rock and ice that orbit the Sun in an extremely elliptical4 orbit. This means that they only come close to the Sun occasionally and when they do they melt and eject dust and gas that appears as a tail. It is this dust and gas that moves in the same orbit as the comet and that causes the meteor storms when the Earth passes through it.
- Meteors: this is small particles (generally no bigger than grains of sand) that collide with the Earth’s atmosphere, are slowed down by the friction between it and the gas in the atmosphere and burn up. As it burns it leaves a trail that we observe as the meteor.
- Meteorites: are objects, larger than meteors, that survive the heat of entering the atmosphere and make it to the Earth. Often they are from the asteroid belt, having been ‘sucked’ in by the Earth’s gravity, but occasionally we find them from other planets, namely the famous Mars meteorite that was thought to contain life. No one has ever been killed by an meteorite though a dog has been hit.
What you need to go meteor watching
It is essential to be prepared when you go to observe meteors, there is nothing worse than having to end a session early from not being prepared well enough. The following is a checklist for items that will defiantly help, though the first is not so easy.
- CLEAR SKIES and a dark location This is necessary if you want to witness the total beauty of this spectacle. The weather is uncontrollable but if you can move away form any forms of light pollution this will greatly increase the number of meteors you can see.
- An unobstructed view Try to get away from trees so that as much of the sky is visible and position yourself facing away from the radiant. This is because most meteors will be moving away from the radiant and you are likely to see more and longest ones.
- Warm Clothing Such as 2 jumpers and a warm jacket and two pairs of trousers (preferably non jeans).
- A woolly hat Yes, this will keep you warm and really is essential as huge amounts of heat is lost through your head.
- Gloves Your fingers will get cold and you wont be able to write, so make sure that you can still write with the gloves on!
- Pen Any pen will do as long as it works.
- Paper This is to record the observations - so if you print out the following tables it is ready for you to fill in straight away! - and plain paper is useful to make any sketches of fire balls etc.
- Sun lounger If possible a chair that can be made flat so that you can lie in comfort off the ground will prevent backache and keep you off the cold ground.
- Warm drink or soup A thermal insulated flask will keep drink warm all night and is a must, it could be filled with a ‘weak lemon drink’ or a soup to give more nourishment (though I have found a drink more useful).
- Food Lots of snacks to keep you awake and functioning. If you are hungry you may not make such good observations. Plus it’s a good excuse to snack all night!
- Company It is always better to observe in a group rather than individually as it’s safer, more enjoyable and you can cover all of the sky.
Below this there is a table that you can print out on which you can record the meteors you see. Send this information to the Perseids Meteor Project run by Jimi X and Beeline to be used for research into the meteor shower. Observations should be made in I hour blocks with a ‘number per minute’ count taken occasionally in the hour.
| Time (Hour) | Number of Perseids | Number per Minute | Number of non Perseids |
|---|---|---|---|
| 1 | = | = | = |
| 2 | = | = | = |
| 3 | = | = | = |
| 4 | = | = | = |
| 5 | = | = | = |
| 6 | = | = | = |
| 7 | = | = | = |
| 8 | = | = | = |
The following table concerns the recording of fireballs, the extremely bright intense meteors that appear as trails more like fire. These are special as could result in meteorites.
| Time of Fireball | Colour | Direction of Travel | Apparent Length of Trail |
|---|---|---|---|
| . | = | = | = |
| . | = | = | = |
| . | = | = | = |
| . | = | = | = |
| . | = | = | = |
| . | = | = | = |
| . | = | = | = |
| . | = | = | = |
| . | = | = | = |
| . | = | = | = |
Please give your results to the perseids meteor project
1ZHR stands for Zenithal Hourly Rate. The zenith refers to when the radiant2 is overhead, and the HR would be expected under ideal conditions at that time.2The radiant is the point from which all the meteors seem to come from, this is found by drawing a line back from each of the meteors and where these cross is the radiant. It follows the same idea as if you look up on a rainy day and all the rain drops will appear to come from one point.3The name if from the two Astronomers who discovered the comet, Dean Swift and Mr. Tuttle, and the comet orbits in 130 years.4an ellipse is a squashed circle, all bodies in the solar system orbit in ellipses though they are very near circles. Ellipses have 2 foci one of which in this case is the Sun
