Stars, Galaxies, and the Universe Chapter 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

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