REVIEW QUESTIONS AFTER VISIT TO THE ROTH PLANETARIUM

Dr. J. L. Regas

Roth Planetarium

Dept. of Geosciences

CSU, Chico

You can use the material below to make up questions after your visit to the Planetarium.

Terminology

Teacher notes:

Astronomers measure the distance to stars in light years.

The light year is the distance that light travels in one year.(Advanced: It equals 9.46 x 10¹⁵ m.) The speed of light is 186,000 miles per second.

The astronomical unit is the average distance between the Earth and the sun. It is abbreviated AU.

Angles are measured in degrees. There are 360° in a circle. A right angle has 90°.

The zodiac is the twelve constellations that the sun moves through.

Questions for students:

1. What is a light year? (Distance that light travels in a year)

2. Polaris is 780 light years away. If you walked outside tonight and look at Polaris, how long ago did the light leave Polaris? (780 years.)

Fundamental Properties of Stars - We will begin with the fundamental properties of stars.

Evaluation: the material in this section is

appropriate for grade _____ and above.

too advanced for grade _______ and below.

1. Why do stars shine (emit light)? (Because they are hot.)

2. Why do that stars that we see look so small? (Because they are so far away.)

3. How do astronomers measure the size of stars when they are looking at them, with miles and meters or with degrees and fractions of degrees. (Degrees) How large is a degree? (Your small finger held at arms length is 1° wide.)

3. Are all stars same brightness? What determines the brightness of stars? (Their distance and intrinsic brightness.)

4. Are all stars same color? (No.) What determines the color of stars? (Their temperature) What does the color of a star tell us about the star? (Its temperature.)

Milky Way Galaxy

5. Is the space between the stars uniformly dark? What do we call the band of light that run across the sky? (Milky Way) What causes this band of light? (The Milky Way Galaxy which contains about 100 billion stars.)

Teacher’s Note:

Galaxy Model: get paper plates and have students draw stars on them. Then have them mark the position of the sun, two thirds of the way out from the center. Show how

the plate spins around. It takes the sun 200 million years to travel around the center of the Galaxy.

6. What is the difference between a galaxy and a solar system? (A galaxy is billions of stars which are rotating about their center. A solar system is a star with planets revolving about the star in the center.)

The Motions of Stars and the Sun.

Evaluation: the material in this section is

appropriate for grade _____ and above.

too advanced for grade _______ and below.

1. What motion of the Earth causes the stars to rise in the east and set in the west every night? (Rotation of the Earth on its axis.)

2. Do the stars in the northern sky rise and set like the stars in the eastern and western skies? ( No.) What star do the stars in the north seen to move around? (North Star, Polaris) What star does the rotation axis of the Earth point toward? (Polaris)

3. What motion of the Earth causes the sun to move each month from one constellation to the next along the Zodiac? (Motion (Revolution) of the Earth around the sun.)

Constellations & Patterns

Evaluation: the material in this section is

appropriate for grade _____ and above.

too advanced for grade _______ and below.

Teaching Strategies:

Use mnemonics - memory tricks.
Build on what students know and are familiar with.
Show northern cross first, then Cygnus. Star Trek Triangle, then Aquila.
Teach students about learning by asking them, what is easier to remember, northern cross or Cygnus, etc. Make them aware of what is easy for them to learn.

1. What are constellations? (Patterns of stars named by ancient astronomers. There are 88 constellations.) The pattern of constellations and the shapes within them help astronomers find the stars in the sky.

Sometimes astronomers find groups of stars that look like letters of the alphabet. Find the "letters of the alphabet" in the patterns of stars in the boxes below.

Sometimes astronomers find groups of stars that look like shapes like triangles or squares. Find the shapes in the patterns of stars in the boxes below.

What constellation is the Big Dipper in? (Ursa Major - Great Bear) What constellation is the Little Dipper in? (Ursa Minor - Little Bear)

2. What star do the Pointers point toward? (Polaris)

3. What do we call the two bright stars at the end of the cup of the Little Dipper that circle around Polaris? (Guardians) Draw a picture of how the stars in the Little Dipper would move during a full 24 hour day.

4. Have your students draw the Big Dipper and Little Dipper on a piece of paper. Have them put Polaris, the North Star, in the center of the paper. Also have your students label the Guardians and the Pointers. With an arrow have them show how the Pointers point to Polaris.

Teacher’s Note:

5. What constellation are the Horse (Mizar) and the Rider (Alcor) in? (Ursa Major) Are these two stars at the same distance from the Earth? (No, Mizar is 58.7 LY away and Alcor is 1/4 LY farther away.)

How close can two stars be together?

6. Why do Mizar and Alcor appear close together in the sky? (Because they are in line with each other as seen from the Earth.)

Two stars can appear close together, but really be far apart.

Teacher note

Mizar and Alcor appear 1/5 of a degree (11.8’ of arc) apart. If two stars are closer together than 1/120 of a degree (0.5’ of arc) they will appear as one star to the eye. Since Mizar and Alcor are 0.2 degrees apart we see them as two stars.

Types of stars

Teacher notes:

When we look at the Horse star (Mizar) in the handle of the Big Dipper though a telescope we actually see two stars, called Mizar A and Mizar B. Because we can see these two stars with our eyes, they are called visual binaries (bi here meaning two stars).

Mizar A and Mizar B are held together by the force of gravity. It will take 10,000 years for these two stars to travel around one another.

Gravity is counterbalanced by the centrifugal force - swinging force, caused by the motion of one star around another.

Mizar A and B are only 14.4" of arc or 380 AU apart. Mizar A (brilliant white, A2 V star) has a magnitude of 2.4 and Mizar B ( pale emerald, A7 p)has a magnitude of 4.0. They take around 10,000 years to travel around their center.

Teacher Notes:

Understanding why stars do not fall into one another.

Questions for students:

1. Get a ball on a string. Why does the ball hang down? (Gravity.)

2. How can you make the ball move out horizontally as shown above? (Swing it or swing it in a circle.)

3. Why don’t Mizar A and Mizar B fall together? (Because they are moving in a circle about each other.)

Teacher Notes - Understanding the Milky Way Galaxy

Questions for students

1. Why doesn’t the sun fall into the center of the Milky Way Galaxy? (Because it is traveling in a circle around the center of the Galaxy.)

Questions for students:

1. Do the Horse (Mizar) and the Rider (Alcor) stars in the Big Dipper travel around each other like the Earth travels around the sun? (Yes.)

2. If you looked at the star Mizar though a telescope how many stars would you see? (Two.)

3. If you watched Mizar A and Mizar B for 10,000 years what would you see these two stars do? (Move in a circle about each other.)

4. What force holds Mizar A and Mizar B together? (Gravity)

5. Why don’t Mizar A and Mizar B fall together because of the force of gravity? (Because they are moving in a circle around each other or because the swinging force (the centrifugal force) keeps them from falling into each other.)

How Astronomers study stars

Astronomers study stars by studying light and radio waves and other types of electromagnetic radiation.

Here is a simple demonstration to show how light behaves as a wave:

Hold your index finger and thumb very close together. Look at a light source through the space between your index finger and thumb. What do you see? Have students sketch what they see.

Astronomers study stars by looking through telescopes.

Telescopes make stars and planets look bigger.
Telescopes let us see two stars that are close together like Mizar A and Mizar B.
Telescopes also let us see stars that are too faint to be seen with the eye.

Astronomers also study stars by passing their light through a glass prism or a diffraction grating.

Solar System

Evaluation: the material in this section is

appropriate for grade _____ and above.

too advanced for grade _______ and below.

Questions for students:

1. What is the difference between a planet and a star? (Stars make their own light while planets get their light from stars. Planets shine with reflected light. Planets move around stars. Stars weigh more; They are more massive.)

2. How do planets move? What do they move around?

3. How do moons get their light? (From stars, the sun) How do moons move? (Around planets.) What do they move around? (Planets)

4. Why don’t the planets fall into the sun because of its strong gravity? (Because they are moving in a circle around the star.)

Lunar Motions and the Observation of the Moon

The time from one new Moon to the next is the Moon's synodic period. It is 29 1/2 days. This is where our month comes from.

As the Moon travels around the Earth it always keeps the same face toward the Earth. This is called synchronous rotation. This occurs because the Moon is tidally locked to the Earth.

The stick I which is driven into the Moon will always point toward the Earth. The Moon always keeps the same face toward the Earth.

How to demonstrate the phases of the Moon. Get a light and have a student hold a tennis ball with a pencil through it.

(Note if you do not have a light, just go outside on a sunny day and use the sun for your light.)

1. Also have other members of the class describe what the person holding the tennis ball will see before they try it.

Eclipses can be demonstrated with a simple light and a tennis ball with a pencil in it.

Why we do not get a lunar and solar eclipse each month.

ECLIPSES

Why does our model incorrectly predict one eclipse of the sun and one eclipse of the moon each synodic month?

The Lives of Stars

Evaluation: the material in this section is

appropriate for grade _____ and above.

too advanced for grade _______ and below.

1. How do stars get their energy? (Gravity and fusion (burning one element into another, frequently hydrogen into helium.) How stars get energy from gravity:

What happens to the ball's kinetic energy after it hits the floor?

( You hear it hit, so some of the energy went into sound. Also the ball was squeezed when it hit the floor, so it was heated. So the energy went into heat and sound.

Evolution of Stars

Teacher Notes: In the sky we see many different types of objects, gas clouds, stable white stars, red giants, planetary nebula, and supernova remnants (What is left over after a star explodes.), white dwarfs and neutron stars. How can we figure out how these are all related?

Good exercise for students: Suppose you walk into a room on back to school night? What do you see? Babies, toddlers, young children, high school students, parents, and grandparents? How could you figure over which came first and which came last? What would you use? (Size, appearance, etc.)

How could astronomers figure out the relation between these different types of stars? What could they use?

High School Teachers’ Supplement

Evaluation: the material in this section is

appropriate for grade _____ and above.

too advanced for grade _______ and below.