Outline: Chapter 12.1: The View From Earth


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Outline: Chapter 12.1: The View From Earth

  1. 1. Chapter 12 Lesson 1 – The View from Earth – p414-419 - page1 Vocabulary  Spectroscope (417) – an instrument that spreads light into different wavelengths  Astronomical Unit (418) – the average distance between Earth and the Sun, about 150 million km  Light-year (418) – the distance light travels in 1 year  Apparent Magnitude (419) – a measure of how bright it an object appears from Earth  Luminosity (419) – the true brightness of an object Looking at the Night Sky  If you look at the stars for a long time they seem to________________.  ________________is a star almost directly above the North Pole.  As Earth spins Polaris stays in place as stars near it seem to circle around it.  Polaris is commonly referred to as the___________________________, because it and the stars near it never ___________when viewed from the northern hemisphere. Naked-Eye Astronomy  Naked-eye astronomy means gazing at the sky using just your eyes; no ___________________ or telescopes.  Before telescopes, people used the stars to tell time, ___________________, and finding directions. Constellations  When ancient cultures gazed at the night sky, they saw_______________________. o They represented people, animals, and objects  The Greek astronomer Ptolemy identified dozens of star patterns nearly ______________ years ago. o These are called ________________ ____________________today  Present-day astronomers use many ancient constellations to divide the sky into ______________regions also called constellations Telescopes  Telescopes are able to collect much more _____________________than the human eye  The _______________________ spectrum is a continuous range of wavelengths o __________________ light is only one part of the spectrum
  2. 2. Chapter 12 Lesson 1 – The View from Earth – p414-419 - page2 o Longer wavelengths have ______________energy o Shorter wavelengths have ______________energy  Different objects in space can emit different types of wavelengths.  The range of wavelengths a star emits is called its__________________________. Spectroscopes  Scientists study the spectra of a star using a___________________________________.  A spectroscope ___________________ light into different wavelengths.  This way, scientists can study a star’s characteristics, compositions, and______________.  Newly formed stars emit mostly _____________and infrared waves. While exploding stars emit high energy _______________________________waves.
  3. 3. Chapter 12 Lesson 1 – The View from Earth – p414-419 - page3 Measuring distance  Astronomers use angles created by __________________ to measure how far objects are from Earth. o Parallax is the apparent change in an object’s ____________________ caused by looking at it from 2 different points. o For example: Look at your pencil with only your left eye. Then, without moving the pencil, look at it with only your right eye.  Astronomers create a parallax by using 2 points in Earth’s ____________________ around the Sun Distance Within the Solar System  Distances ________________ the solar system are measured using astronomical units or AU.  An astronomical unit is the average distance between Earth and _____________________ , about 150 million km. Distances Beyond the Solar System  Astronomers measure distances ___________________ the solar system using light-years. o A light-year is the distance light travels in 1 year. o 1 light-year equals about 10 _______________________km.  The nearest star to our Sun is 4.2 light-years away. How far is that in km? Looking Back in Time  Because it takes time for light to travel, you see a star not as it is______________, but as it was when light left it.  At 4.2 light-years away, Proxima Centauri appears as it was ______________ years ago. Measuring Brightness  Astronomers measure the brightness of stars in two ways: o By how bright they appear from Earth o By how bright they actually are Apparent Magnitude  Scientists measure how bright stars appear from __________________ using a scale developed by the ancient Greek astronomer Hipparchus o Hipparchus assigned a _______________ to every star he saw in the night sky based on its brightness.  Today these are called __________________ _____________________ o The apparent magnitude of an object is a measure of how bright it appears from Earth  Hipparchus assigned the number __________ to the brightest star he saw in the night sky
  4. 4. Chapter 12 Lesson 1 – The View from Earth – p414-419 - page4 Absolute Magnitude  Stars can appear bright or dim depending on their __________________ from Earth, but stars also have actual, or absolute, magnitudes  __________________________is the true brightness of an object  This depends on the star’s _____________________and size rather than its distance from Earth  A star’s luminosity, distance, and apparent magnitude are all_____________________. Thus, if a scientist knows two of these factors, he can mathematically determine the third. Apparent Magnitude Scale