Lesson 1: What is a star?
Stars and Light
Have you sat outside on a clear night and looked at the sky? Did you see any stars? A star is a giant ball of hot, glowing gases that release energy. Light from stars takes time to reach Earth. Light travels 300,000 kilometers per second. That is fast! Light from the sun, a star, takes about eight and a half minutes to reach the Earth. Light from other stars takes longer. The distance light travels from stars is measured in light years. A light year is the distance light travels in one year.
Types of Stars
You may see thousands of stars on a clear night. All stars except the sun look like points of light because they are very far away. Some stars appear brighter than others.
Scientists use physical characteristics such as brightness, size, color, and temperature to describe stars. Stars can produce different amounts of light. The sun is a very bright star. It is the closest star to Earth. It may seem that bright stars in the night sky are closer to Earth than dim stars. Actually, some stars that appear dim may be closer to Earth than bright stars. A star’s distance from Earth is not the only reason it appears bright. Other features affect the brightness of stars besides its closeness to Earth.
Our sun and most stars in the universe are similar. However, stars can be different sizes. For example, the size of our sun is average. Some stars are larger than our sun. Other stars are smaller. Over time, the size of a star can also change.
Patterns of Stars
Groups of stars can be found in distinct areas of the sky. Some groups of
stars seem to make patterns or shapes. You can imagine lines drawn between
stars to make each pattern. These are called constellations.
The stars that make up these patterns look like they are close together
in space. They really are very far apart. Some stars are farther from Earth than
others. If you look at the same stars from far away in space, they would not make
the same pattern. The pattern of stars also change with Earth’s seasons. As Earth moves around the sun, these patterns are in different parts of the sky.
Can you answer these questions? How are stars different? Why do stars often look like points of light?
Lesson 2: What is the sun?
Our Sun
Our sun is the closest star to Earth. It is a ball of hot, glowing gases. The sun looks larger and brighter than stars you see at night because it is closer to Earth. The other stars in the sky look like points of light because they are far away.
How big is the sun? In one word—huge! It is 109 times as wide as Earth, or wider than the length of 15,000,000 football fields! In fact, the sun is large enough to hold 1,000,000 Earth’s inside it! Now that’s huge!
Sun’s Energy
Like all stars, the sun gives off a lot of energy. Energy from the sun travels out in all directions through space. Some of the sun’s energy travels to Earth as visible light. This visible light travels to Earth as waves. Some of the sun’s light energy that reaches Earth is used by plants to grow and make food. Like other sources of light, such as fire and some light bulbs, the sun’s light gives off heat.
Did you know that the sun has cycles? One cycle is the solar cycle. The sun produces different amounts of energy during this cycle. This variation in energy can produce solar flares. These solar flares give off a lot of energy. The energy from solar flares can cause interruptions on Earth. For example, stronger solar flares an interrupt communications among satellites and cell phones.
Can you answer this question?
Why does the sun look large and bright in our sky while other stars look like little points of light?
Lesson 4: What is a telescope?
View from Earth
Have you ever looked through a telescope?
A telescope is a tool that makes distant objects appear closer, larger,
and easier to see. Telescopes magnify light from distant objects using
tubes and mirrors or lenses. These parts bend and bounce light. The result
is a larger, clearer view of objects.
Kinds of Telescopes
Some telescopes collect and magnify visible light. They use mirrors
to make objects appear larger. The Keck telescope and Hubble Space
Telescope use mirrors to see objects in the sky. These telescopes are
called optical telescopes.
Another kind of telescope searches for radio waves. Radio stations
send out radio waves. Objects in space also send out radio waves.
Radio telescopes collect and measure these waves. Radio telescopes help scientists find objects that optical telescopes cannot find. For example, radio telescopes help scientists find durst clouds in dark parts of space.
Can you answer this question?
How do telescope help scientists learn about stars?
Lesson 5: What is radiant energy?
Radiant Energy
Have you sat outside in the sun on a hot day? Did your skin feel warm? Your skin feels warm because of radiant energy from the sun. Radiant energy is the energy in the form of light and other similar waves. Have you ever run on a hot beach? Radiant energy from the sun can heat the sand on the beach. After the sun sets, the sand and other objects on Earth can cool down.
Radiant Energy and Matter
Radiant energy can affect the temperature of matter. Have you ever felt warm at a park on a sunny day? Radiant energy from the sun can heat the slides and other objects at the park. When the sun is not present, heat may be lost. Nights are usually cooler than days. That is because parts of Earth’s atmosphere do not receive energy directly from the sun during the night.
Different types of matter absorb radiant energy differently. Have you ever gone swimming on the first hot day of summer? The pavement may be hot, but the water might still be chilly. This is because the temperature of liquids increase more slowly than that of solids. Solids warm up faster than liquids. They also cool off faster. Think of the swimming pool later in the summer. At night the water stays warmer than the pavement around it.
Sometimes, radiant energy from the sun can cause matter to change states. For example, radiant energy can cause ice to melt. Below 0° C (32°F), water becomes ice. Radiant energy can cause the temperature to increase. When the temperature increases above 0° C, ice melts.
Can you answer this question?
How does radiant energy effect objects that are in a park on a very hot day?
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