Sun & Stars

Which of these has the most impact on the apparent brightness of a star seen from Earth?

• gravitational pull

• temperature of a star

• distance from Earthf

• Earth's orbital pattern

The picture shows us how the Sun's rays strike Earth. Because of the Earth's tilt on its axis, some parts of Earth are having summer, and others, winter. What letter or letts on the Earth are experiencing winter?

• A

• A and B

• D

• A and D

We know that Earth makes a complete revolution around the sun once every 365 days, following an elliptical orbit. This means that the distance between the Earth and Sun, which is 93 million miles on average, changes throughout the year. We also know that the seasons are caused by the fact that the Earth is tilted on its axis by 23.5^o. This tilt in Earth's axis does not change during the year.

Check the image of the Earth's orbit around the Sun. Imagine you live at the place marked by the red spot, in the United States and in the northern hemisphere. Find the label in the diagram that says "winter solstice". Compare the day length and the time the sun is in the sky with the "summer solstice". Provide an explanation for your answer.

• The day length is shorter because the Northern Hemisphere is tilted away from the sun.

• The day length is shorter because the Earth is at its farthest point in the orbit around the sun.

• The amount of sunlight during the year does not change; the angle of the sun in the sky changes so the light seems dimmer.

• The day length for both the winter and summer solstice is the same because the Earth is at about the same distance from the sun.

What would happen if you went outside one night and recorded the location of the moon? Then, on the next night, at the exact same time you went out on the first night, you go outside again. The stars will be in almost the same part of the sky as they were the first night. But the moon will be in a different place! Why?

• The Earth is spinning on its axis in space.

• The Earth orbits the Sun and spins on its axis.

• The moon is spinning on its axis as is the Earth.

• The moon is moving in a month-long orbit around Earth.

Sean goes outside and notices that the sun looks larger than the other stars he has seen. Why does the sun appear larger than the other stars?

• The Sun is the largest star in the sky.

• The Sun looks larger because of the rotation of the Earth.

• The Sun looks larger because it is closer to Earth than any other star.

• The Sun appears to be the largest star because it gives off the most light.

Why does the Sun appear larger and brighter as seen from Earth than the other stars in the chart? Use the table to help you answer the question.

• It is hotter

• It is larger

• It is closer

• It is yellow

The Northern and Southern Hemispheres experience opposite seasons and different day lengths, no matter what time of year. What is the best explanation for these variations in seasons and daylight?

• The Moon orbits in a path around the hemisphere not facing the Sun.

• The hemisphere experiencing winter is the farthest away from the Sun.

• Earth's axial tilt changes direction as it orbits the Sun, causing seasonal patterns.

• Earth's axial tilt causes one side of Earth to be exposed to the Sun than the other.

Scientists group stars by color and

• alike and different

• temperature

• brightness

The smallest, coolest stars are

• blue giant stars

• red dwarf stars

The brightest stars are

• red dwarf stars

• blue giant stars