Chapter 12 Lesson 1 The View from Earth p414-419 - page4VocabularySpectroscope (417) an instrument that spreads light into different wavelengthsAstronomical Unit (418) the average distance between Earth and the Sun, about 150 million kmLight-year (418) the distance light travels in 1 yearApparent Magnitude (419) a measure of how bright it an object appears from EarthLuminosity (419) the true brightness of an object

Looking at the Night SkyIf 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 AstronomyNaked-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.

ConstellationsWhen ancient cultures gazed at the night sky, they saw_______________________.They represented people, animals, and objects

The Greek astronomer Ptolemy identified dozens of star patterns nearly ______________ years ago.These are called ________________ ____________________todayPresent-day astronomers use many ancient constellations to divide the sky into ______________regions also called constellations

TelescopesTelescopes are able to collect much more _____________________than the human eyeThe _______________________ spectrum is a continuous range of wavelengths__________________ light is only one part of the spectrumLonger wavelengths have ______________energyShorter wavelengths have ______________energyDifferent objects in space can emit different types of wavelengths.The range of wavelengths a star emits is called its__________________________.

SpectroscopesScientists study the spectra of a star using a___________________________________.A spectroscope ___________________ light into different wavelengths.This way, scientists can study a stars characteristics, compositions, and______________.Newly formed stars emit mostly _____________and infrared waves. While exploding stars emit high energy _______________________________waves.

Measuring distanceAstronomers use angles created by __________________ to measure how far objects are from Earth.

Parallax is the apparent change in an objects ____________________ caused by looking at it from 2 different points.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 Earths ____________________ around the Sun

Distance Within the Solar SystemDistances ________________ 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 SystemAstronomers measure distances ___________________ the solar system using light-years.A light-year is the distance light travels in 1 year.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 TimeBecause 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 BrightnessAstronomers measure the brightness of stars in two ways:By how bright they appear from EarthBy how bright they actually are

Apparent MagnitudeScientists measure how bright stars appear from __________________ using a scale developed by the ancient Greek astronomer HipparchusHipparchus assigned a _______________ to every star he saw in the night sky based on its brightness.Today these are called __________________ _____________________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

Absolute MagnitudeStars can appear bright or dim depending on their __________________ from Earth, but stars also have actual, or absolute, magnitudes__________________________is the true brightness of an objectThis depends on the stars _____________________and size rather than its distance from EarthA stars 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