Unit 4Chapter 30

What is Astronomy?

In this Chapter, we will cover:

30.1 Cycles on Earth

30.2 Tools of Astronomy

Chapter 30 Learning Goals Relate keeping track of time to astronomical cycles. Predict how the moon will appear based on its

orbital position. Describe what causes the seasons and eclipses. Convert large numbers to scientific notation. Name the differences between stars, planets,

galaxies, and the universe. Convert between kilometers and light years. Explain how refracting and reflecting telescopes

work. Name some telescopes that examine other types of

electromagnetic waves. Describe how satellites, space probes, and piloted

spacecraft are used in astronomy.

Chapter 30 Vocabulary Terms

axis

calendar galaxy

light year

lunar eclipse

planet

reflecting telescope

refracting telescope

revolution

rotation

satellite

scientific notation

solar eclipse

star

telescope

universe

30.1 Cycles on Earth

Key Question:

How do we keep track of time?

30.1 Cycles on Earth

The development of a calendar came from a need to be able to predict the seasons, annual floods, and other cyclical occurrences in communities’ lives.

A calendar is a means of keeping track of all

the days in a year.

30.1 Phases of the Moon

The moon moves around Earth in a path called an orbit.

How the moon appears to Earth dwellers at different positions in its orbit is shown below:

The phases of the moon occur because of the positions of Earth, the moon, and

the sun.

Moon Phases

30.1 Cycles on Earth

Earth’s axis is the imaginary line that passes through its center and connects the North and South poles.

Earth’s spinning on its axis is called rotation and it brings about day and night.

The movement of one object around another in space is called revolution.

Earth’s path as it revolves around the sun is called its orbit.

One year (365.25 days) is the amount of time it takes Earth to complete one revolution around the sun.

30.1 Cycles on Earth

What causes seasons?

30.2 Tools of Astronomy

The closest star to our sun, Alpha Centauri, is 41,000,000,000,000 km away.

Trying to write out astronomical distances requires a lot of zeros.

Scientific notation is a mathematical abbreviation for writing very large (or very small) numbers.

The universe is defined as everything that exists, including all matter and energy.

A star is a sphere of gas that undergoes a process called fusion. This process releases so much energy, the star gives off very bright light.

A planet is a large, spherical piece of matter that revolves around a star.

30.2 Tools of Astronomy

A light year is the distance light travels in one year through space (9.46 × 1012 kilometers).

ex. How many light years away is Alpha Centauri, the closest star to our sun?— Remember this star is 4.1 trillion km away...

4.1 x 1013 km ? light years=

30.2 Tools of Astronomy

4.1 x 1013 km ? light years=

xlight year1

9.46 x 1012 km4.1 x 1013 km

= 4.3 s

30.2 Tools of Astronomy

A satellite is an object that travels in orbit around another object.

The Hubble Space Telescope (or HST) is a satellite that orbits Earth. This powerful telescope sends images from deep space to computers back on Earth.

30.2 Tools of Astronomy

Space probes are unmanned spacecraft that carry scientific instruments on board.

30.2 Tools of Astronomy

Space shuttles are piloted spacecraft that launch from rocket “boosters” and can land back on Earth like an airplane.

A space shuttle consists of three big components: two solid rocket boosters (SRBs), an external fuel tank, and an orbiter.

30.2 Tools of Astronomy

Key Question: How does a telescope work?

*Read text section 30.2 BEFORE Investigation 30.2

30.2 Tools of Astronomy