Meteor showers and comets
On certain nights each year you can see many more shooting stars than usual. This lesson explains why, and how to watch a meteor shower safely.
- Explain what causes a meteor shower.
- Name two meteor showers and the dates they peak.
- Count meteors and work out a rate per hour.
Links to: Year 5 science, Earth and space: Earth's orbit around the Sun; working scientifically: taking measurements and recording data; maths: multiplication and rates.
Following a comet's trail
As a comet travels around the Sun, it leaves a trail of dust behind it along its orbit. Most of the dust grains are no bigger than grains of sand.
Earth travels around the Sun once a year, so it crosses the same dust trails on the same dates every year. When it does, lots of grains hit the air and burn up as meteors. This is a meteor shower. The grains are so small that they burn up completely, high above the ground, so meteor showers do not drop meteorites.
The best showers
The Perseids peak around 12 to 13 August, on warm summer nights. Their dust comes from Comet Swift–Tuttle. The Geminids peak around 13 to 14 December and are often the richest shower of the year. Unusually, their dust comes from an asteroid called Phaethon rather than a comet.
The meteors in a shower all seem to come from one spot in the sky, called the radiant. Each shower is named after the constellation where its radiant is: the Perseids seem to come from Perseus and the Geminids from Gemini.
How to watch
Go somewhere dark, away from street lights, with an adult. Lie back on a blanket or reclining chair, dress warmly and let your eyes get used to the dark for about 20 minutes. Do not look at a phone screen, because its light undoes that. You do not need a telescope, as meteors move too fast for one. Just look at a wide area of sky and be patient.
Meteors per hour
During the Perseids, you count 9 meteors in 15 minutes. If they keep arriving at the same rate, how many would you see in one hour?
- There are 60 minutes in an hour, and 60 ÷ 15 = 4, so an hour is 4 lots of 15 minutes.
- Multiply the count by 4: 9 × 4 = 36.
Answer: About 36 meteors per hour. Real counts go up and down, so astronomers count for a long time and then work out the rate.
On a clear night near a shower peak, count meteors with an adult for 15 minutes using a tally chart, then work out the rate per hour. If it is cloudy, use the events calendar on this site to find the next shower and make a viewing plan: date, place, what to wear and what to bring.
Quiz
5 questions. Choose an answer to see whether you are right and why. Finish the quiz to complete the lesson.
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Question 1What causes a meteor shower?
Comets leave dust along their orbits. When Earth crosses a trail, many grains burn up as meteors.
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Question 2When do the Perseids peak?
The Perseids peak in mid-August every year, because Earth crosses the dust trail of Comet Swift–Tuttle at the same point in its orbit.
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Question 3What is the radiant of a meteor shower?
All the meteors in a shower appear to spread out from one point, which gives the shower its name.
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Question 4Why don't meteor showers drop meteorites?
Shower meteors come from tiny grains of comet dust, which are destroyed long before they could reach the ground.
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Question 5You count 5 meteors in 10 minutes. At the same rate, how many in an hour?
An hour is 6 lots of 10 minutes, and 6 × 5 = 30.