Size, Distance, & Motion

Objective 1 Compare the size and distance of objects within systems in the universe.

Use the speed of light as a measuring standard to describe the relative distances to objects in the universe (e.g., 4.4 light years to star Alpha Centauri; 0.00002 light years to the sun).

Compare distances between objects in the solar system. Compare the size of the Solar System to the size of the Milky Way galaxy. Compare the size of the Milky Way galaxy to the size of the known universe.

Objective 2 Describe the appearance and apparent motion of groups of stars in the night sky relative to Earth and how various cultures have understood and used them.

Locate and identify stars that are grouped in patterns in the night sky. Identify ways people have historically grouped stars in the night sky. Recognize that stars in a constellation are not all the same distance from Earth. Relate the seasonal change in the appearance of the night sky to Earth's position. Describe ways that familiar groups of stars may be used for navigation and calendars.

Standard 4

Students will understand the scale of size, distance between objects, movement, and apparent motion (due to Earth's rotation) of objects in the universe and how cultures have understood, related to and used these objects in the night sky.The BIG Idea

How Far is Far?

Average of 238,000 Miles

Earth to Moon Distance

93,000,000 Miles1 Astronomical Unit (AU)

Sun to Earth Distance

Body AU Mercury .39Venus .72Earth 1.0Mars 1.5Jupiter 5.2Saturn 9.5Uranus 19.2Neptune 30.1Pluto 39.5

Solar System Model Diameter Orbital Radius Model Diameter

Scaled RadiusBody in Miles in Miles in Inches in Feet

Sun 865,000 9

Mercury 3,032 36,000,000 .0314

31

Venus 7,521 67,000,000 .0782

58

Earth 7,926 93,000,000 . 0823

81

Mars 4,228 141,000,000 . 0437

123

Jupiter 88,846 483,000,000 .9021 419

Saturn 74,898 886,000,000 .7528

769

Uranus 31,763 1,782,000,000 .3035 1,546

Neptune 30,775 2,794,000,000 .2937

2,425

Pluto 1,423 3,666,000,000 .0 140 3,186

Calculating Distance

Viewpoint B

Viewpoint A

Viewpoint A Viewpoint B

Parallax

Parallax

Viewpoint B

Viewpoint A

Proxima Centauri

Alpha Centauri A & B

Our Nearest Neighbors

4.2 Light-Y

ears

5 Light-Y

ears

100,000 Light-Years

The Size of Galaxies

The Galactic Neighborhood

2 Million Light-Years

Light travels at a speed of 186,000 miles per second.

Nothing can travel faster than light.

The Speed of Light

If the Sun is 93,000,000 miles away from Earth, how long does it take light to travel from the Sun to Earth’s surface?

Think About It

A spaceship flying from the Earth to the Sun would take about a year, yet light takes just eight minutes to cross the same vast distance.

In one year how many miles can light travel?

Think About It

We call this distance a light year. The farther away a star or galaxy is from

Earth, the longer its light takes to reach us.

The nearest star after our the Sun is more than 4 light years away - Proxima Centauri

The nearest galaxy to our own is 2 million light years away – Andromeda Galaxy

A Light Year

186,000 miles/second

The Light-Year

X 60 minutes/hour X 24 hours/dayX 365 days/year

X 60 seconds/minute

5,865,696,000,000 miles/year

A galaxy is a family of billions of stars held together in space by the pull of gravity.

Galaxies are not evenly spread out through the universe.

Arranged in great sheets, strings, and groups. Large families are called clusters. Many clusters of galaxies are grouped into even

larger families, called super-clusters. Galaxy shapes – spiral, barred spiral, and elliptical

galaxies.

Galaxies

Classifying Galaxies

Our home, a spiral galaxy. 100 billion stars. Belongs to a cluster of about 30 galaxies scattered across 3 million light years.

The Milky Way

Hubble Deep Field Image

Imaginary star pictures Named for animals or mythological

characters Astronomers recognize 88

constellations Different constellations are visible in

the night sky at different times of the year. Why?

Constellations

Win

ter

Su

mm

er

Polaris (a.k.a. the North Star) Found in the constellation Ursa Minor

(the little bear). Ursa Minor is also known as the Little

Dipper. The last star in the handle.

Which way is north?

Astronomers use constellations as a kind of map to find their location on Earth – navigation.

Also used as a map of the sky. Can tell us what season it is. For entertainment.

Why do we need constellations?