Stars and Galaxies

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Chapter 22

• Stars and Galaxies

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Lesson 1 STARS

• Constellations patterns of stars
• Represents mythological characters,
• animals or familiar objects.
• Modern astronomy divides sky into 88
  constellations.
• Stars are found in specific
• locations in sky
• Polaris, Sirius, Betelgeuse

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Circumpolar Constellations

• Ursa Major Ursa Minor and others APPEAR to
  circle around POLARIS (North Star) .
• Are visible ALL YEAR LONG
• Other constellations come and go in the sky due
  to Earths revolution around Sun.

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http//www.astropix.com/HTML/SHOW_DIG/Big_and_Litt
le_Dippers.HTM
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Some stars look brighter why?

• Absolute Magnitude measure of the amount of
  light start gives OFF.
• Apparent Magnitude measure of the amount of
  light RECEIVED on Earth.
• A dim star can appear bright if closer to Earth.
• A bright star can appear dim if it is far away
  from Earth.

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Measurement in Space

• One Way PARALLAX
• The apparent shift in the position of an object
  when viewed from two different positions.
• THE NEARER AN OBJECT IS to the observer, the
  GREATER the parallax is.
• Example thumb

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Measurements

• Light-year distance light travels in 1 year
• 300,000 km/s or 9.5 trillion km in 1 yr.
• AU average distance Earth is from Sun 150
  million km.
• Luminosity true brightness of an object.
• Use Luxes measure light intensity.
• Closest Star to Earth?
• SUN
• After Sun, Proxima Centauri 4.2 light years
  away.

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Characteristics of Stars temp, composition and
energy

• Color temperature
• HOT are blue white color.
• Cool are orange red color
• Yellow our SUN
• Composition observing spectra
  (like a prism)
• Light passes thru a spectroscope (spreads light
  into different wavelengths) - breaks into colors
  (like a rainbow) w/ dark lines in between.
• Lines tell us what elements are in the star.
• Every chemical element produces a unique pattern
  of dark lines just like a finger print.
• Can also tell energy level
• Low energy newer stars emit radio infrared
  waves.
• Higher energy exploding stars emit ultraviolet
  x-rays.

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Our Suns Spectrum
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Assignment

• Read Ch 22 Lesson 1
• DO your note cards or foldables for Lesson 1
• Use both NOTES book.
• DO P. 806 (1-8 only)

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Lesson 2 Our Sun

• Why so important?
• Makes life possible!
• Center of our System.
• Source of most energy
• on Earth

In Universe Just an ordinary Yellow
Main Sequence
Unique in one way IT IS NOT BINARY (Pair of
stars orbit each other)
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Structure
List Inside to Atmosphere A. Core where
fusion takes place which is Suns
energy. B. Radiation Zone how Energy travels
outward C. Convection Zone(circulates) how
Energy travels outward and circulates
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Atmosphere

• D. Photosphere where light is
• given off (lowest layer of atmosphere)
• Often called the surface
• E. Chromosphere above photosphere
• F. Corona
• largest layer of atmosphere. (Rays you
  drew off a circle when you were little ? )
• Charged particles escape from here and create
  Solar Wind.

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Surface Features

• NOT smooth !
• Sun rotates faster at equator than at poles.
• Sunspots
• Area that appear darker than rest.
• Cooler than surrounding area.
• Intense magnetic fields.
• Ever since Galileo weve been studying them!
• Not permanent appear and disappear.
• 11 yr. cycle of min. and max. of sunspots.

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More Features .

• Prominences HUGE, arching columns of gas.
• Think they are related to intense Magnetic Field
  of SUNSPOTS.
• Flares violent eruptions gases near a sunspot
  sometimes brighten and then shoot out at high
  speed.
• CMEs coronal mass ejections
• Usually occur during Sunspot Maximums
• Highly charged solar wind material
• Cause Auroras (Northern Lights) electrical
  currents that ionize gas in Earths atmosphere.
• Can disrupt radio signals power outages, etc.

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Pictures / Videos of what is happening on Sun

• Video of CMEs hitting Earth
• video of sun
• 4 min. video of explanation of how sun works

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H R Diagram

• Most stars fit into MAIN SEQUENCE.
• Usually temp. is at the bottom.
• Notice Brighter stars have Magnitudes w/ neg.
  numbers. (Intensity goes UP.)

KNOW hottest / brightest top left
coolest / faintest lower right
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Assignment

• Read Lesson 2
• Do note cards / foldables for Lesson 2
• Do worksheet on H-R diagram.

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Section 3 Evolution of STARS

• Two Important diagrams NEED to know how to
  read them!!!
• 1) H-R Diagram Hertzsprung and Russell
  (scientists)
• Stars arranged by brightness and temperature
• Shows (USUALLY) the hotter the star the
  brighter the star.
• 2 ) Life of a Star Diagram handout.
• Shows how star evolves.
• Two paths depends on mass of star.

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How do stars shine?

• Temps are so high causes Hydrogen to FUSE into
  Helium!
• REACTION causes high amounts of energy to be
  released.
• Happens in the CORE of STARS only place w/
  temps high enough.

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Evolution of a STAR P. 749
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Two Paths

• High Mass Stars
• NEBULA all stars beginning Def large cloud of
  gas dust
• Main Sequence - most stars until uses up
  its Hydrogen!!
• Red Supergiant - core contracts causes temp to
  increase then COOLS
• Supernova outer portion of star explodes (def
  huge explosion that destroys a star)
• Neutron Star consists only of Neutrons in dense
  core
• Black Hole core collapses until there is no
  volume gravity so great nothing can escape -
  not even LIGHT
• Low Mass Stars
• NEBULA all stars beginning
• Main Sequence
• Red Giant
• White Dwarf - leftover core hot dense slowly
  cooling sphere of carbon.

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Cycle starts over again.

• Leftover material goes into a NEBULA
• Matter is reused New star is formed

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Section 4 Galaxies in Universe

• Definition of Galaxy
• Large group of stars, gas, and dust held together
  by
• gravity.
• Universe consists of hundreds of billions of
  galaxies.
• Most galaxies are in clusters not spread evenly
  in universe.

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Galaxies

• Types of Galaxies
• Spiral has arms
• Elliptical looks like a football oval shape
• Irregular all the rest that dont fit into the
  other 2 categories.
• Our Galaxy Milky Way Ours is w/ the Local
  Group (about 30 galaxies)
• Think its a SPIRAL but could be barred (have
  bars)
• Sun is NOT in center one of the arms orbits
  around

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Universe

• EVERYTHING in space.
• 90 is DARK Matter (Matter that emits no light
  at any wavelength.)
• Scientist used Doppler Shift to learn that -
• UNIVERSE is expanding
• Doppler Shift
• RED
• object moving away
• wavelengths of light stretch (expand)
• BLUE
• object moving toward
• wavelengths of light compress

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Big Bang Theory

• 12 to 15 billion yrs ago, universe began w/
  explosion
• Everything is expanding from that explosion
• Once again Catholic Scientist came up w/ the
  idea

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End of Chapter ?

• Review WS
• Thurs TEST over Ch 22
• (Got your note cards or foldables done??)
• You have been reviewing vocab, right?