Chapter 28 – Stars and Galaxies

  1. A Closer Look at Light

A.  What is light?

1.  Light is a form of ______(EM)

2.  Other types of EM listed from longest to ______wavelengths

a.  Radio

b.  ______

c.  Infrared

d.  Visible light

e.  ______

f.  x-rays

g.  Gamma rays

-  This is known as the ______All EM energy travels in waves and at the speed of light

3.  Can travel through ______(vacuum)

B.  Spectroscope

1.  Visible white light is actually made up of light of various ______each with a ______wavelength

2.  The various color can be observed

a.  In a ______

b.  Passing light through a ______

c.  Or an astronomers instrument known as a ______

3.  The colors ROY G. BIV are aligned from longest to shortest (______)

4.  Longer wavelengths ______less

C.  Types of spectra from spectroscopes

1.  Continuous spectrum – ______band of colors which are emitted by

a.  Glowing ______(filament)

b.  Glowing ______(molten iron)

c.  Hot compressed ______(inside stars)

2.  ______spectrum – lines of ______colors

a.  Produced by glowing thin gases

i  Each element has its own ______therefore scientists can identify the gas

3.  ______spectrum – a continuous spectrum crossed by dark lines

a.  Elements in the thin _____ that surround a ______absorb the same wavelength they would emit

b.  The stars ______spectrum indicates the composition of the stars ______

-  The sun radiates a continuous spectrum, however, the gases in the atmosphere ______some wavelengths. By analyzing the ______bands, scientists can figure out the composition of the sun’s ______.

c.  ______spectrum can also determine a planets atmosphere

D.  Doppler Effect

1.  By observing how the spectral lines are shifting, scientists can tell how a star is moving compared to the earth

a.  Move to the red end, “______,” the star is moving ______

b.  Move to the blue end, “______,” star is getting ______

c.  By using spectrums from the lab and the stars, they can determine how ______they are moving

  1. Stars and Their Characteristics
  2. Constellations – ______given to groups of stars
  3. There are ______of them

2.  Big dipper – best known asterism (______star grouping) is actually part of a larger grouping known as ______

  1. We can use the dipper to find other ______
  1. The stars appear to move in two ways
  2. Nightly variation – due to ______

b.  Yearly due to earth’s ______

-  ______– winter constellation

-  ______– summer constellation

  1. ______magnitude
  2. Is the ______of the star as seen from ______
  3. The lower the number, the ______it is

-  ______is –26.7

-  Faintest is +6

  1. Distance to stars
  2. Astronomical Unit (AU) distance from ______– 150 million km
  3. Proxima Centauri – next nearest star is ______AU

3.  Therefore, astronomers use ______-years – a unit of measure that light travels in one year.

a.  Light travels about ______/sec è 1 year = 9.5×1012

  1. Proxima Centauri is about ______light years away
  2. Elements in Stars
  3. Stars are mostly of super-hot gases – mostly ______
  4. Mass, Size and Temperature of Stars

1.  ______is something that can not be observed directly. It can only be ______based on other observations

  1. Stellar mass is expressed as multiples of the sun’s mass

______mass – 20 solar masses

  1. Temperature and Color
  2. Blue stars are ______
  3. Red stars are ______
  4. Luminosity
  5. The ______brightness of the star is luminosity
  6. If two stars have the same ______, the larger star would be more luminous
  7. If the same size, ______one would be brighter
  8. Types of magnitude
  9. ______– as if all stars were same distance from earth ______– as they appear in the nighttime skyVariable Stars
  10. Some stars show regular variation of brightness over cycles that last from days to years

6.  ______Variables – yellow supergiants whose cycles range from 1 to 50 days

  1. If a cepheid is located in another galaxy, astronomers can find the ______to these galaxies by comparing absolute and ______magnitudes
  2. Other stars change in brightness because they revolve around ______. This is known as a ‘______star system.’

  1. Life Cycles of Stars
  2. Hertzsprung-Russel Diagram

1  A diagram to help explain a stars ______

2  Most stars fall into _____ distinct groups

  1. Main sequence – ______of stars

-  Our sun

  1. ______– 10-100x bigger than our sun – more luminous
  2. ______– more than 100x bigger than our sun
  3. White ______– stars near the end of their lives
  4. Birth of a Star

1  Stars begin their life as a ______

  1. Huge cloud of ______
  2. Death of a Star

1  2 paths

  1. nebula à protostar à main sequence à red giant à planetary nebula à white dwarf
  2. nebula à protostar à massive star à red supergiant à supernova à blackhole or neutron star

c.  our sun will swell into a ______, then its outer layers will get blown away and only an earth-sized fiery hot carbon-oxygen core will remain (white dwarf)

  1. Remnants of Massive Stars

1  Massive star goes ______, the core that is left behind is so massive that the electrons of elements are pulled into the nucleus forming a ______.

2  Some neutron stars spin rapidly, burst of radio waves, these are known as ______

3  ______hole – so dense that their gravity will not even let ______escape

  1. Galaxies and the Universe
  2. What are galaxies

1  A system of ______of stars that appear as a ______star in our sky

2  There is between ______billion galaxies

3  There are millions of light years between galaxies

4  Sun belongs to the ______Galaxy which is a ______galaxy

5  Milky Way belongs to the Local Group of about ______galaxies

  1. Types of galaxies

1  ______– like the Milky Way

2  ______– spherical to lens shaped

3  ______– much smaller and fainter with no shape

C.  Active Galaxies

1  Galaxies that emit more energy than their combined stars are said to be ______

2  Currently it is thought that super massive ______are at the center of these galaxies