AST 115 - HW 1

How far from Earth is the Moon?

1 light second

Which of the following is smallest? (**** is correct)

1. 1 AU 2. 1 light-second 3. size of a typical star 4. size of a typical planet****

Which of the following statements does not use the term light-year in an appropriate way? (**** is correct)

1. It will take the Voyager spacecraft about 20,000 years to travel just 1 light-year. 2. It will take me light-years to complete this homework assignment.**** 3. It's about 4 light-years from here to Alpha Centauri. 4. A light-year is about 10 trillion kilometers. 5. The Milky Way Galaxy is about 100,000 light-years in diameter.

Which of the following statements about the Milky Way Galaxy is not true? (**** is correct)

1. Our solar system is located very close to the center of the Milky Way Galaxy.**** 2. One rotation of the galaxy takes about 200 million years. 3. The galaxy is about 100,000 light-years in diameter. 4. It contains between 100 billion and 1 trillion stars.

Which of the following is largest? (**** is correct)

1. size of Pluto's orbit 2. size of a typical galaxy**** 3. 1 light-year 4. distance to the nearest star (other than our Sun)

Approximately, what is the age of the Universe?

14 billion years

How long does it take our solar system to complete one orbit around the Milky Way Galaxy?

230 million years

How far from Earth is the nearest star besides the Sun?

4.2 light years

Approximately, what is the age of the Earth?

4.5 billion years

If traveling at the speed of light, approximately how far could you travel in one second?

7x around the Earth

How far from Earth is the Sun?

8.3 light minutes

Suppose we imagine the Sun to be about the size of a grapefruit (about 10 cm across). What describes the size and distance of Earth on the same scale?

Earth is the size of a poppy seed about 10 meters away from the Sun.

Earth is always precisely 1 AU from the Sun. T or F?

False.

The solar system contains about 250 billion stars. T or F?

False.

One light year is about 10 trillion kilometers. T or F?

True.

The solar system is a member of a galaxy containing approximately 250 billion stars. T or F?

True.

On the scale of the cosmic calendar, in which the history of the universe is compressed to 1 year, how long has human civilization (i.e., since ancient Egypt) existed?

a few seconds

On a scale where the Sun is about the size of a grapefruit and the Earth is about 10 meters away, how far away are the nearest stars besides the Sun?

about the distance across the United States

On a cosmic calendar, in which the history of the universe is compressed into 1 year, when did the dinosaurs become extinct?

late December

How many galaxies are there in the observable universe?

roughly (within a factor of 10) the same as the number of stars in our galaxy

An astronomical unit (AU) is ________.

the average distance between Earth and the sun

What is the ecliptic plane?

the plane of Earth's orbit around the Sun

The total number of stars in the observable universe is about ________.

the same as the number of grains of sand on all the beaches on Earth