stars, galaxies, and the universe chapter 21.1 & 21.2

Stars, Galaxies, and the

UniverseChapter 21.1 & 21.2

Telescopes• Electromagnetic Radiation

- energy that can travel through space

in the form of waves

• Electromagnetic Spectrum

- the entire range of radiation

Telescopes

• Telescopes are instruments that collect and focus light and other forms of electromagnetic radiation.

• Telescopes make distant objects appear larger and brighter

Telescopes

• 3 kinds of telescopes

- Optical telescopes

1) Refracting telescopes

– use convex lenses

The larger the lens, the stronger the telescope

Largest Refracting Telescope

The Great Paris Exhibition Telescope of 1900

1.25 m diameter

Telescopes

2) Reflecting Telescopes

- use concave mirrors

The larger the mirror, the stronger the telescope

Largest Reflecting Telescope

Large Binocular Telescope

Mount Graham International Observatory, Arizona

Two 8.4 m diameter

Subaru Telescope

Hawaii

8.2 m diameter

Telescopes

- Radio Telescopes – devices used to detect radio waves from objects in space

The larger the dish, the stronger the telescope

Telescopes

Largest radio telescopes

Arecibo, Puerto Rico

1,001 ft

Telescopes

• Observatory – a building that contains one or more telescopes

• Usually located on mountain tops or in space

Hubble space telescope is a reflecting(optical) telescope

• why do we study the stars?

Characteristics of Stars

• Constellations –

imaginary patterns

of stars in the sky

Classifying Stars

• Stars are classified using color and temperature

Hottest

Coldest

Classifying Stars

Stars are classified using size

Classifying Stars

Stars are classified according to composition

Brightness of Stars

• The brightness of a star depends on both its size and temperature

• A large star may look bright, even though it is relatively cool, because of its size

• A small star may look bright because it is hot

Brightness of Stars

Apparent Brightness- how bright a star appears from Earth

Brightness of Stars

Absolute Brightness- how bright a star would be at a standard distance

Measuring Distances to Stars

Light-year – distance light travels in a year

- used to express distance

between stars

-speed of light = 300,000 km/s

1 light-year is about 9.5 million million kilometers

• how to measure extreme distances

Measuring Distances to Stars

Parallax – the apparent change in position of an object when you look at it from different places

Parallax can be used to measure stars that are only a few hundred light-years away

• What is Parallax? - YouTube

Hertzsprung-Russell Diagram

Plotting of stars on a graph based on temperature and absolute brightness

Used to understand how stars change over time