chapter 1 our place in the universe

Copyright © 2012 Pearson Education, Inc.

Chapter 1Our Place in the Universe


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

Star


Planet

A moderately large object that orbits a star; it shines by reflected light. Planets may be rocky,

icy, or gaseous in composition.

UranusMars


Moon (or satellite)

An object that orbits a planet

Ganymede (orbits Jupiter)


Asteroid

A relatively small and rocky object that orbits a star

Mathilde


Comet

A relatively small and icy object that orbits a star


Solar (Star) System

A star and all the material that orbits it, including its planets and moons


Nebula

An interstellar cloud of gas and/or dust


GalaxyA great island of stars in space, all held

together by gravity and orbiting a common center

M31, the Great Galaxy in Andromeda

M31, the great galaxy in Andromeda

Chapter 1: Our Place in the Universe

One difference between the terms solar system and galaxy is that:

A. the solar system contains only one star but the galaxy contains many billions.

B. the solar system contains planets, but the galaxy does not.

C. other galaxies are rare, but other solar systems are common.

D. other solar systems are rare, but other galaxies are common.


Universe

The sum total of all matter and energy; that is, everything within and between

all galaxies


Key Definition: Light-Year

• The distance light can travel in 1 year

• About 10 trillion kilometers (6 trillion miles)


Put these objects in the correct order, from nearest to farthest from Earth:

A. The Sun, the Milky Way, Alpha Centauri, Pluto, the Andromeda galaxy

B. The Sun, Alpha Centauri, Pluto, the Andromeda galaxy, the Milky Way

C. The Sun, Pluto, Alpha Centauri, the Milky Way, the Andromeda galaxy

D. Pluto, the Sun, Alpha Centauri, the Milky Way, the Andromeda galaxy




The sun – a star ~93 million miles away~150 million kilometers~ 8 light-minutes




Pluto – a “dwarf planet” ~3 billion miles away~48 billion kilometers~ 4.5 light hours




Alpha Centauri – a star~26,000 billion miles away~4.2 x 1013 kilometers~ 4.5 light years




Milky Way – a galaxy ~200 billion stars~100,000 light years across~ 27,000 light years to center




Andromeda – another galaxy~400 billion stars~2.5 million light years away


Which is farther, the distance from San Francisco to Los Angeles, or the distance from you to the International Space Station, when it passes directly overhead?

A. San Francisco – LA is further

B. The space station is further


Which is farther, the distance from San Francisco to Los Angeles, or the distance from you to the International Space Station, when it passes directly overhead?

A. San Francisco – LA is further!!

B. The space station is further


In a scale model solar system that used a grapefruit to represent the Sun, how large would the Earth be?

A. The size of an orangeB. The size of a marbleC. The size of the point of a ballpoint penD. The size of a bacterium


In a scale model solar system that used a grapefruit to represent the Sun, how far away would the Earth be?

A. 6 inches

B. 1 foot

C. 5 feet

D. 40 feet

E. 1 mile


In a scale model solar system that used a grapefruit to represent the Sun, how far away would Pluto be?

A. 100 feet

B. 200 feet

C. 2,000 feet

D. 10 miles


In a scale model solar system that used a grapefruit to represent the Sun, how far away should you put another grapefruit to represent Alpha Centauri, the next nearest star?

A. 10 feetB. 1,000 feetC. 1 mileD. 10 milesE. 1,500 miles


How can we know what the universe was like in the past?

• Light travels at a finite speed ( 186,000 miles/second = 300,000 km/s).

Destination Light travel time

Moon 1 second

Sun 8 minutes

Sirius 8 years

Andromeda Galaxy 2.5 million years


How can we know what the universe was like in the past?

• We see objects as they were in the past:

The farther away we look in distance, the further back we look in time.

Look far enough away, and we look back in time to when the universe was much younger…


Example:

This photo shows the Andromeda Galaxy as it looked about 2 ½ million years ago.


• At great distances, we see objects as they were when the universe was much younger.


How big is the universe?• The Milky Way is one of about 100 billion galaxies.

• 1011 stars/galaxy 1011 galaxies = 1022 stars

It has as many stars as grains of (dry) sand on all Earth’s beaches.


How is Earth moving in our solar system?

• Contrary to our perception, we are not “sitting still.”

• We are moving with the Earth in several ways, and at surprisingly fast speeds.


Earth rotates on its axis:

A. Once a day

B. Once a week

C. Once a month

D. Once a year

E. Once every 250,000 years


How is Earth moving in our solar system?

Earth rotates around its axis once every day.


Earth revolves around the Sun:

A. Once a day

B. Once a week

C. Once a month

D. Once a year



Earth orbits the Sun (revolves) once every year…

• at an average distance of 1 AU ≈ 150 million km.• with Earth’s axis tilted by 23.5º (pointing to Polaris).• and rotates in the same direction it orbits, counter- clockwise as viewed from above the North Pole.


The Moon revolves around Earth:

A. Once a day

B. Once a week

C. Once a month

D. Once a year



The Moon revolves around Earth:

A. Once a day

B. Once a week

C. Once a moonth

D. Once a year



Earth revolves around the Milky Way Galaxy:

A. Once a dayB. Once a weekC. Once a monthD. Once a yearE. Once every 230 million years


Our Sun moves randomly relative to the other stars in the local solar neighborhood…

• at typical relative speeds of more than 70,000 km/hr• but stars are so far away that we cannot easily notice their motion

… and it orbits the galaxy every 230 million years.


Are we ever sitting still? Earth rotates on axis: > 1,000 km/hr

Earth orbits Sun: > 100,000 km/hr

Solar system moves among stars: ~ 70,000 km/hr

Milky Way rotates: ~ 800,000 km/hr

Milky Way moves in Local Group

Universeexpands


Why do we not feel or sense the various motions of Earth in the universe?

A. They are not real, they are just models

B. They are too slow to sense

C. They are nearly uniform, and you can not sense uniform velocity, only acceleration, which is a change of velocity or direction


Suppose that, at this very moment, students are studying astronomy on planets in Andromeda. Could they know that we exist here on Earth?

A. Yes, because we can see stars in Andromeda, so they can see us in the Milky Way.

B. No, the light from the solar system has not yet reached Andromeda.C. No, the light from the solar system that has reached Andromeda came

from a time before Earth had formed.D. No, radio signals from terrestrial civilizations have not yet reached

Andromeda.E. Yes, in principle. With sufficiently powerful telescopes, they should be

able to see man-made features such as the Great Wall of China on Earth’s surface.


Suppose that, at this very moment, students are studying astronomy on planets in Andromeda. Could they know that we exist here on Earth?

D. No, radio signals from terrestrial civilizations have not yet reached Andromeda.

chapter 1 our place in the universe

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