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# Shooting Stars: Why are Meteors Hot?

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Source:
Author: Janice VanCleave

### Problem

Why are meteors hot?

### Materials

• bulb-type thermometer
• writing paper
• pencil

### Procedure

1. Press the bulb of the thermometer between the palms of your hands. Record the temperature on the thermometer after 15 seconds or more. Caution: Take care not to press so hard as to break the thermometer.
2. Set the thermometer aside and rub the palms of your hands together as you count slowly to 10.
3. Immediately repeat step 1.

### Why?

Particles from comets, asteroids, or even moons and planets that float around in space are called meteoroids. Meteoroids from comets are generally very small, lightweight specks of dust while meteoroids from other celestial' bodies are generally larger and heavier. Most of the larger meteoroids come from asteroids.

When a meteoroid enters Earth's atmosphere, it is referred to as a meteor. Because it is moving so fast, the meteor is heated by friction (resistance of one body moving against another body) with air to a state of incandescence (glowing hot) and burns up. The particle as well as the glow it produces are both called a meteor. Most meteors are specks of comet dust. Large meteoroids create such brilliant meteors that they are called fireballs. The friction between your hands as you rub them together produces heat just as meteors do when they rub against air as they move through Earth's atmosphere.

### Let's Explore

Meteoroids enter Earth's atmosphere at speeds of 22 to 60 miles (35 to 95 km) per second. How does the speed of a meteoroid affect how much it is heated as it moves through Earth's atmosphere? Repeat the experiment, rubbing your hands together as quickly as possible.

### Show Time!

1.
1. Meteors appear as bright streaks of light across the sky. These flashes of light are commonly called shooting stars. On a dark, clear night, in an open area clear of trees or buildings, Sit in a lawn chair so that you can observe the eastern sky. Record the time when you start your observations. Study the sky for 1 hour or more, counting the number of shooting stars you see. Record the time when you stop observing and determine the total number of hours of observation time. Calculate the average number of shooting stars per hour. For example, if during an observation time of 2 hours, 16 shooting stars are seen, the number of shooting stars per hour would be:
16 shooting stars ÷ 2 hours = 8 shooting stars per hour
2. Are meteors seen more in the east than in the other compass directions: west, north, or south? Repeat the experiment with three friends. Have each person face one of the four compass directions. For best results, repeat the experiment on as many nights as possible. Average the results for each direction.
3. Is the path of meteors generally random in direction, or do meteors come from a specific direction? While counting the meteors in the previous experiment, make note of the direction each meteor comes from. Use a star chart, similar to the one shown here, to plot the path of the meteors. A star with a tail can be the symbol of a meteor. Constellations can be added for reference. For charts of constellations visible in different seasons, see pages 224–227 in Janice VanCleave's Constellations for Every Kid (New York: Wiley, 1997).
2. As a comet orbits the Sun, it leaves behind a band of meteoroids that follow the comet's orbit. When Earth, moving along its orbit around the Sun, passes through the band of meteoroids, many meteors are seen coming from one part of the sky. This occurrence is called a meteor shower. Repeat the three previous experiments during a meteor shower. Some of the dates for meteor showers are listed here. For a more detailed listing and more information about each of the showers, see page 96 in David H. Levy's Skywatching (San Francisco: Time Life/Nature Company, 1995).

### Important Annual Meteor Showers

 January 2–3 April 20–22 May 4–6 August 10–13 October 8–10 October 18–23 November 8–10 December 10–12

### Check It Out!

Meteor showers are usually named for the constellation from which they seem to originate, such as Orionids from the direction of Orion. Find out more about meteor showers. What is a radiant? Why are meteors more plentiful after midnight? For information, see page 292 in Dinah L. Moche's Astronomy (New York: Wiley, 1996).