1 Chapter 12 Objectives: 1)List the major objects that can be seen in our night sky. 2)Define a light year and be able to convert it to distances. 3) Define nebulae and explain its connection to stars. 4)Identify the parts of a star. 5)Compare star color to star temperature. 6)Explain the life cycle of stars using the Hertsprung-Russell Diagram. Know the different possibilities for the death of a star. 7)Define galaxy. Be able to distinguish between the three types of galaxies. 8)Detail the Milky Way Galaxy. 9)Define constellation. List some of the more common constellations found in our night sky.

2 Chapter 12 The Universe I) The Night Sky A) Objects to View 1)Nighttime viewing includes: p_________ and m______ (chapter 13), s_______, c______________, n_______, and g__________.

3 2) Great distances separating objects in the universe can be simplified using the _______ ______, (ly). a) 1.0 ly equals ____________ or __________. This is the distance _______ travels in one ______. b) Our Milky Way galaxy is approximately 6.0 X miles across. How long will it take light (or radio signals) to travel across our galaxy?

4 II) Origin of Stars A) Nebulae 1) Nebulae: swirling clouds of ________ gas in deep space between other stars. a) As the particles move closer together their gravitational attraction takes over and a __________ is born.

5 b) When enough particles condense in the protostar, the kinetic energy of the particles create enough heat to begin nuclear ________; hydrogen particles merge to form __________, (___). B) The Parts of a Star 1) The Parts

6 a) _______: the very dense center where nuclear fusion takes place. b) ____________ zone: less dense than the core (about the density of ________); area where radiation from the core interacts with particles outside the core (about the distance from the earth to the _______). c) ____________ zone: The outer ___% of the diameter of the sun. Is made of p______ with a density about 1.0% that of _______.

7 III) Brightness of Stars A) Stars are ___________; they emit their own light. 1) The classification for the different brightness’ of star light is called _________ _________; see chart aside. a) S_______ is the brightest star in our night sky; but check out the apparent magnitudes of the planets, moon, and sun.

8 IV) Star Temperature A)Besides their different brightness, stars also differ in _______. 1)The _______ of a star is due to its ____________. a) TemperatureColor

9 V) Star Types and the Life of a Star A) Hertzberg-Russell Diagram B) Star’s Lifecycle *Protostar-Main Sequence- Red Giant- Main Sequence- Death? 1) _________ Stage: dust and gas coming together to begin nuclear fusion.

10 2) _____ ___________ Stage: the star makes it to the main sequence category on the H-R diagram; its mass determines its length of stay (millions to trillions of years; the sun  __________ years). 3) ____ _______ Stage: most of the core is helium and the lack of outward pressure (from the nuclear fusion) causes the star to begin collapsing; now the hydrogen layer outside the core begins nuclear fusion and causes the star to expand much larger than it had before (the Sun will be larger than the earths orbit). 4) Back Toward ______ ___________: the helium core now begins nuclear fusion and the size of the star decreases back to the main sequence category.

11 5) The Beginning of the End: a) For a Less Massive Star (about the size of the Sun or smaller):  The core becomes _________ with layers of nuclear fusion of both ________ and ________ around it.  As temperatures cool the star ___________, which increases the temperature again; blowing off its outer materials into space creating a _________ ________.  The core eventually cools and becomes a black lump of carbon.

12 b) For Massive Stars:  More nuclear fusion takes place in the core until ______ is produced.  The star collapses, then explodes into a _______ _____.  Most massive stars will now be left with an iron core and be classified as a _____ star; if it generates a magnetic field then it is called a ________.  Stars __ times more massive than our Sun will collapse on itself for infinity; thus creating a _____ ____.

13 VI) Galaxies A)_________: a grouping of billions and billions of stars that form a basic part of the universe. 1) Types: a) ___________ Galaxy: b) ___________ Galaxy:

14 c) ___________ Galaxy: 2) Galaxies group with each other to make a ________ _________; galactic clusters group together to form a _______ cluster.

15 B) The _______ ____ Galaxy: The galaxy of which our solar system belongs. 1) The Parts and the Sun’s Location:

16 2) The Stars We see at Night: a)All the stars we see belong to the ________ _____ ________. b) Stars can be grouped into particular shapes known as _______________. c) Constellations:

17 * mostly named to honor gods and heroes from ancient times and civilizations. *today, ___ modern constellations exist. *twelve of the ___ belong to the _________ constellations (_________ means “circle of animals). *Other prominent constellations include: