Science Module 8, Lesson 08.03

Science Module 8, Lesson 08.03

The Sun, Stars, and Patterns

What will I learn in this lesson?

I will be able to

-use evidence to create an argument that the apparent brightness of the Sun and stars is due to their relative distances from the Earth

-use data to show patterns of daily changes caused by Earth's position in the Solar System

Distance and Brightness

A star is a ball of burning gas in space that emits its own light. Some stars appear larger than others, some appear smaller, and some appear brighter. The brightest star that you can see from Earth is the one closest to Earth, which is the Sun.

Distance and Brightness

The Solar System is enormous, making the distance between two objects very large. When you discuss distances in the Solar System, you use the relative distance instead of the actual measurements. Relative distance compares the distance of one object to another specific object. 

Distance and Brightness

Even though all stars are millions of kilometers away, some are closer to Earth than others. A star that appears dim is farther away from Earth than a star that appears brighter. How bright a star appears from Earth is called the apparent brightness of a star. The apparent brightness helps you determine the relative distance of a star from Earth.

Did You Know?

Distance can impact how bright a star appears from Earth. Our Sun is the brightest and largest star we can see from Earth. It appears bright and large because it is the closest star to us. There are other stars that are much larger than the Sun, but because they are so far away, they seem much smaller and dimmer. 

Not Always as They Appear

The farther away the star, the dimmer its apparent brightness. Stars appear dimmer when they are farther away because of their relative distance to Earth.  

Not Always as They Appear

Serius appears to be one of the brightest stars in the sky. You can easily see it without a telescope. As you get closer to Serius, its apparent brightness increases.

Practice Like a Scientist- Optional

How does the light appear when it is closer and farther away?

You will need the help of a trusted adult for this activity. The trusted adult will take a flashlight and shine it on you from a close distance and from farther away. You will then describe the apparent brightness of the light and how this relates to the relative distance. 

Finding the Evidence

What if you wanted to convince your friends that stars in the sky appear brighter because their relative distance to Earth is closer? What type of evidence would you need to convince your friends? This can be tricky. Read the article and find some evidence!

Write Like a Scientist- Optional

Use the following article to gather evidence that can support the following statement: "A star that is farther away from Earth will appear dimmer than a star that is closer to Earth." 

Use your Science Notebook to write down evidence that you will use later to support your argument.

A Constellation

of Stars

When you look at the night sky, you will see that some stars appear brighter than other stars. Night after night, these same bright stars will appear and form a pattern, which is called a constellation. A constellation is a group of stars that form a pattern. Why do the stars in the constellation appear brighter than the other stars?

Star Light,

Star Bright

Stars, which vary in size, also range greatly in their relative distance from Earth. The closer a star is to Earth, the brighter it appears. This is why the Sun, which is a star, appears to be the brightest star in the universe. The Sun is much, much closer to the Earth than any other star!

Relative Distance

of the Stars

The Sun is the closest star to Earth. From Earth, the Sun gives off so much light that you cannot see other stars in the sky until the nighttime. From space, it is easier to see the relative distance between the Earth and the Sun, and the Earth and other stars. 

Relative Distance

of the Stars

The Sun is much closer to Earth compared to other stars. From Earth, the apparent brightness of other stars appear dimmer than the Sun because they are farther away from Earth than the Sun.

Street Lights, Stars, and Apparent Brightness

If you observe a series of streetlights, you will notice the light closest to you is brighter than the lights farther away. All of the street lights are the same, but the light closer to you appears brighter because of its relative distance to you. This means a light closer to you will appear brighter than the same light farther away from you.

Street Lights, Stars, and Apparent Brightness

You can use the example of streetlights to better understand the apparent brightness of the stars. Stars closer to Earth will appear brighter than stars farther away. Since the relative distance of the Sun to Earth is closer than the relative distance of other stars to Earth, the Sun appears to be the brightest star in the sky.

Did you know: Stars can form shapes in the sky called constellations?

A constellation is a group of stars that appear in a recognizable pattern. Ursa Major, which means "big bear," can best be seen in the Northern Hemisphere during the spring. The rectangle is the body of the bear, and the three stars that trail behind make up the tail.  

Ursa Major

Don't see a bear? That’s okay. Most people recognize part of this constellation as the Big Dipper because it looks like a big spoon.

Multiple Choice

The _ is the distance an object in our Solar System is from another object, like Earth or the Sun.

• relative distance

• apparent brightness

Multiple Choice

When stars are farther away they appear to look dimmer, why is this?

• Because the street lights are too bright

• Because of their position in the sky

• Because of their relative distance to Earth

• Because the other stars are brighter

Multiple Choice

What is it called when stars form a pattern in the sky?

• Apparent brightness

• A constellation

• A star pattern

• A galaxy

Multiple Choice

Why do other stars appear dimmer than the Sun?

• Because the Sun is the brightest star

• Because they are farther away from Earth

• Because they are not as bright as the Sun

• Because they are closer to Earth

Movement of

the Earth

As Earth orbits the Sun, it rotates on its axis. One complete rotation of Earth on its axis takes about 24 hours or one day. The Earth is facing different parts of the Sun as the day goes on. This results in the repeating pattern of day and night. As Earth orbits the Sun, it also causes a change in the seasonal appearance of some stars that you can observe in the night sky. 

Movement of

the Earth

The Earth also has a slight tilt that creates patterns of daily changes in length and direction of shadows from day to night.  

Earth also has a slight tilt that creates patterns of daily changes in the length and direction of shadows from day to night.  

What causes day

and night?

As the Earth rotates on its axis over 24 hours, the position of the Sun in the sky changes. In this case, the part of Earth facing the Sun is experiencing daytime. 

The Earth's rotation on its axis!

The same part of the Earth that was facing the Sun in the previous image is now facing away from the Sun. This part of the Earth is now experiencing nighttime.

Practice Like a Scientist- Optional

The Earth is always moving. It rotates on its axis and revolves around the Sun. Think of a basketball spinning on the tip of your finger. The spinning basketball is like the Earth rotating on its axis. Now, imagine if you walked in a circle around an object, say a chair. When you walk all the way around the chair, you have completed one revolution. 

Practice Like a Scientist- Optional

If you put the two motions together by walking around the chair while spinning the ball on your finger, then you’re modeling how Earth rotates while it orbits the Sun.

Print the Movement of Earth activity sheet and follow the instructions provided.

Creating Shadows

Have you ever tried to catch your shadow? You will find it an impossible feat as the shadow will constantly move as you try to chase it. Catching a friend's shadow is very doable, especially if you are chasing shadows early in the morning or late in the day when the Sun is low in the sky.  

Creating Shadows

The position of the Sun affects the length of a shadow! When the Sun is low in the sky, the length of shadows are longer than they are during the middle of the day. Therefore, if you are trying to catch your friend's shadow, it is easier when the shadow is longer! 

Let's take a closer look at how the Sun's position affects the length of a shadow.

Casting Shadows

Throughout the course of a day, the Sun appears to rise and move across the sky. The Sun rises in the east as nighttime becomes day, reaching its highest point in the sky at noon and then sets in the west as daytime becomes night. 

Casting Shadows

What is responsible for the pattern of night and day? 

Although it appears like the Sun is moving, it’s actually the rotation of Earth on its axis that leads to the pattern of day and night.

Creating Shadows

The position of the Sun in the sky also affects the shadows it creates on Earth. 

What time of day would you find the shortest shadows?

If you were to place a wooden stake in the ground, the Sun would create the shortest shadows at noon when it is highest in the sky.

Multiple Choice

The picture shows a shadow late in the day when the Sun is low in the sky.

• True

• False

Multiple Choice

The picture shows a shadow late in the day when the Sun is low in the sky.

• True

• False

The Sun and Shadows

The position of the Sun creates shadows of different lengths that repeat in patterns from day to day. When the Sun is low in the sky, either in the morning or evening, shadows are longer. Around noon, when the Sun is high in the sky, shadows are shorter.

The Sun and Shadows

The position of the Sun also determines the direction of the shadow. If you are facing the Sun, your shadow will be behind you. A shadow will appear in the opposite direction of the Sun because the object is blocking the light coming from the Sun.

Shadow Talk

The length of the shadow depends on the angle at which light is falling on the object. Since the position of the Sun changes throughout the day, the angle at which the Sun's rays hit the ground also changes.

Shadow Talk

In the morning, the Sun is low in the sky. The light hits you sideways, which makes your shadow appear longer on the ground.

Shadow Talk

By noon the Sun is at its highest point in the sky. When the Sun is directly above you, its light comes straight down at you, making your shadow appear shorter.

Shadow Talk

By the evening, the Sun is back at a low angle. The light comes at you sideways, and your shadow is longer again, but this time the light is coming from the opposite direction so your shadow has now moved to the other side.

Practice Like a Scientist- Optional

In this activity, you will measure the length and direction of a shadow at different points throughout the day. You can use your own shadow, or you can pick a tall object around you. You are encouraged to work on asphalt or a cement surface so you can use chalk to draw lines and directions. Follow the instructions provided on page 9.

Seasonal Patterns

of Stars

Earth is constantly rotating on its axis as it orbits the Sun. When you look at the night sky and observe the stars, you’re observing a slightly different part of the galaxy.

The group of stars and constellations you can observe may change throughout the year and from season to season. The stars you can see repeat in pattern as Earth revolves around the Sun.

Practice Like a Scientist- Optional

The patterns in the stars you see at night depend on the position of Earth as it revolves around the Sun. The stars that you see each night may change from season to season as the Earth continues on its orbit around the Sun.

Lesson Summary

You learned that the apparent brightness of the Sun and stars is due to their relative distances from Earth. The closer a star is to Earth, the brighter and larger it appears. You also learned that the Sun's position in the Solar System affects the patterns of shadows and stars. 

Lesson Summary

If you observe your shadow throughout the day, you will notice that the length and size of your shadow is larger early in the morning and late in the day, and shorter around noon. The position of the Sun creates shadows of different lengths that repeat in the same pattern from day to day.

Lesson Summary

The position of the Earth in the Solar System changes the star patterns you are able to see throughout the year. Constellations that you see each night may change from season to season as Earth continues to orbit the Sun.

Multiple Choice

What causes day and night?

• Sunrise and sunset

• The Earth’s rotation on its axis

• The time of day

• The moons appearance in the sky

Multiple Choice

When do shadows appear the shortest?

• 4 p.m.

• 12 p.m.

• 6 a.m.

• 6 p.m.

Multiple Choice

Why do stars appear dimmer when they are farther away?

• Stars appear dimmer because of daytime and nighttime.

• Stars appear dimmer because they are made of a different material.

• Stars appear dimmer because there are other objects in the way.

• Stars appear dimmer because of their relative distance to Earth.