Chapter 1

Question 1

What unique view did a NASA camera aboard the Deep Space Climate Observatory (DSCOVR) satellite capture?

Answer 1

The fully illuminated “dark side” of the moon

This view is of the moon as it moved in front of the sunlit side of Earth.

Question 2

On what date did the Curiosity rover land on Mars?

Answer 2

August 6, 2012

This event marked a significant milestone in Mars exploration.

Question 3

What significant event occurred on February 15, 2013?

Answer 3

Chelyabinsk meteor

This meteor exploded over Russia, causing damage and injuries.

Question 4

What is the purpose of the James Webb Space Telescope?

Answer 4

To observe astronomical objects and phenomena

Launched on December 25, 2021, it aims to enhance our understanding of the universe.

Question 5

What is the timeline for the Artemis missions?

Answer 5

• Artemis I: Uncrewed lunar flyby (Nov. 2022)
• Artemis II: Crewed lunar flyby (April 2026)
• Artemis III: Crewed landing on the moon (2027)

The last crewed landing on the moon was in 1972.

Question 6

What are the three parts of the PHYS 171 course overview?

Answer 6

• Developing perspective (Chapters 1-3)
• Key concepts for astronomy (Chapters 4 and 5)
• The solar system (Chapters 6-10)

Each part covers different aspects of astronomy.

Question 7

What are the key concepts for astronomy covered in Chapters 4 and 5?

Answer 7

• Motion
• Energy
• Gravity
• Light

These concepts are fundamental to understanding astronomical phenomena.

Question 8

What is the cosmic address of Earth?

Answer 8

Earth is part of the solar system, which is in the Milky Way Galaxy, which is a member of the Local Group of galaxies in the Local Supercluster

This hierarchy illustrates our place in the universe.

Question 9

Define a star.

Answer 9

A large, glowing ball of gas that generates heat and light through nuclear fusion

Stars are fundamental components of galaxies.

Question 10

Define a planet.

Answer 10

A moderately large object that orbits a star and shines by reflected light

Planets can be rocky, icy, or gaseous in composition.

Question 11

What is a dwarf planet?

Answer 11

A celestial body that has not cleared its orbital path

Dwarf planets include Pluto and others.

Question 12

What is a moon?

Answer 12

An object that orbits a planet

Moons can vary greatly in size and composition.

Question 13

Define an asteroid.

Answer 13

A relatively small and rocky object that orbits a star

Asteroids are primarily found in the asteroid belt between Mars and Jupiter.

Question 14

Define a comet.

Answer 14

A relatively small and icy object that orbits a star

Comets are known for their spectacular tails when near the sun.

Question 15

What is a nebula?

Answer 15

An interstellar cloud of gas and/or dust

Nebulae are often the birthplaces of stars.

Question 16

Define a galaxy.

Answer 16

A great island of stars in space, all held together by gravity and orbiting a common center

The Milky Way is one such galaxy.

Question 17

What is the observable universe?

Answer 17

The boundary of the observable universe is about 14 billion light years away from us

The entire universe is estimated to be much larger.

Question 18

What is a light-year?

Answer 18

The distance light can travel in 1 year, about 10 trillion kilometers (6 trillion miles)

Light-years are used to measure astronomical distances.

Question 19

How long would it take to count the more than 100 billion stars in our galaxy at a rate of one per second?

Answer 19

A few thousand years

This illustrates the vast number of stars in the Milky Way.

Question 20

What is the estimated number of stars in the universe?

Answer 20

About 10^22 stars

This is comparable to the number of grains of sand on all Earth’s beaches.

Question 21

What is the cosmic calendar?

Answer 21

A scale on which we compress the history of the universe into 1 year

This helps visualize the timeline of cosmic events.

Question 22

What significant event occurred on January 1 in the cosmic calendar?

Answer 22

The Big Bang

This marks the beginning of the universe.

Question 23

What significant event occurred on September 22 in the cosmic calendar?

Answer 23

Early life on Earth

This indicates the timeline of biological development.

Question 24

What is the average distance of Earth from the Sun in AU?

Answer 24

1 AU ≈ 150 million km

AU stands for Astronomical Unit, a standard unit of measurement in astronomy.

Question 25

How often does Earth **rotate** around its axis?

Answer 25

Once every day ## Footnote This rotation is responsible for the day-night cycle.

Question 26

How often does Earth **orbit** the Sun?

Answer 26

Once every year ## Footnote This revolution defines the length of a year.

Question 27

What is the tilt of Earth's axis?

Answer 27

23.5º ## Footnote This tilt affects seasonal changes on Earth.

Question 28

What direction does Earth rotate and orbit as viewed from above the North Pole?

Answer 28

Counter-clockwise ## Footnote This consistent direction is observed in both rotation and orbit.

Question 29

At what speed does our Sun move relative to other stars in the local solar neighborhood?

Answer 29

More than 70,000 km/hr ## Footnote This speed is typical for stars in our vicinity.

Question 30

How long does it take for the Sun to orbit the center of the **Milky Way**?

Answer 30

230 million years ## Footnote This period is often referred to as a cosmic year.

Question 31

Who discovered that the universe is **expanding**?

Answer 31

Hubble ## Footnote Hubble's observations led to the conclusion that galaxies are moving away from us.

Question 32

What did Hubble find about galaxies outside our **Local Group**?

Answer 32

* All are moving away from us * The more distant the galaxy, the faster it is racing away ## Footnote This observation supports the theory of an expanding universe.

Question 33

True or false: We are **sitting still** in the universe.

Answer 33

FALSE ## Footnote Earth is in constant motion, rotating and orbiting, along with the movement of the solar system and galaxies.

Question 34

What is the **conclusion** about the movement of galaxies within the universe?

Answer 34

We live in an expanding universe ## Footnote This conclusion is based on the observation of galaxies moving away from each other.