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The biggest show on Earth

Have you ever seen a shooting star? If not, now’s your chance.

What is a shooting star?

The proper name for a shooting star is a meteor. It is a tiny piece of space dust that hits the Earth’s atmosphere. It burns up almost instantly due to friction with the air and because it hits the atmosphere so fast. The tiny particles are in orbit around the sun and travel at about 29 to 42 Km per second.

Meteor

The actual speed the particles hit the Earth is often much faster than this because the Earth is also orbiting the sun. This is about 44 miles per second, or Cardiff to London in 3 seconds, 212 times the speed of a rifle bullet.

When do meteors hit the Earth?

You stand a chance of seeing a meteor at any time of the year as the Earth is struck by about 40 tonnes of cosmic debris per day. But you’d have a better chance of seeing them in August. This is when the biggest shower of the year happens. It is called the Perseids. The best shower of the year happens in November, the Leonids.

What’s with all the ids?

Why are the showers given such strange names? It’s all to do with where they appear to come from in the sky. If you look at the photo, all the meteors seem to come from one point in the sky called the radiant.

The radiant for the Perseids is in the constellation of Perseus. The radiant for the Leonids is in the constellation of Leo. Get the idea? So if you know the name of the shower you have got a pretty good idea of where to look for it in the sky.

Why do showers happen at certain times of the year?

The Earth goes around the sun in a very nearly circular orbit. Sometimes there are other things that cut across this orbit. Comets often do this. They come hurtling in from the depths of space and are often trapped into long elliptical orbits that cut across the path of the Earth.

Comets are very scruffy things. The name actually means ‘hairy star’, and they do indeed moult! They shed millions of tiny particles into the space all around them. These tiny particles follow the same orbit as their comet. Eventually, the particles get spread all around the comet’s orbit. This means that every time the Earth crosses the comet’s path, it collides with all the leftover bits and a meteor shower happens.

Comet breaking up

Why do they all appear to come from the same spot?

This is actually an optical illusion. The Earth is running into the stream of particles. The trails just look as if they converge. It’s like looking at a pair of railway lines disappearing into the distance. You know they must be parallel, but your eyes and brain tell you they are getting closer together. This is a ‘perspective’ effect. Artists use it all the time to make a flat canvas look as if it has depth. The most dramatic demonstration happens if you stand outside in a heavy rain shower and look straight up. What do you see?

When do meteors happen?

The four best showers of the year:

Can I become a meteor spotter?

Yes, and the darker the sky, the better. So if you live in the country, great! You can still see them in cities, but you won’t see as many. There are always some that are very bright. The Leonids in particular always produce a number of ‘fire balls’! These are very bright meteors that can be seen from anywhere. Some even leave a luminous trail that last for minutes. Ever heard of Halley's Comet?

Halley's Comet

Lie on a sun lounger and point yourself in the direction of the constellation of the radiant (a star chart helps) and wait. They arrive in a completely random pattern. Sometimes you will see nothing for a while. See how many artificial satellites you spot while you’re waiting for the meteors. You may be surprised at how many you can see. They look like steadily moving stars that sometimes get brighter or fade.

The International Space Station (ISS) is so bright you can see it in daylight if you know where and when to look. At night it is truly spectacular. If you want to know when you can see it, follow the links!

The International Space Station

Can you do real science?

Yes! Record the direction and brightness of each meteor on your star chart. The really interesting bit is that you may find out that some of the meteors don’t come from the main shower. If they just point in random directions they are known as ‘sporadics’, but sometimes you will find that they all point to same spot in the sky, a different radiant to the main shower. You may have discovered a new shower!

The big questions:

What at are ‘shooting stars’?

How can I observe them?

Why do they occur at certain times of year?