Unit 11 Stars, Galaxies,

1
Unit 11Stars, Galaxies, the Universe
2
Section 1 Tools of Modern Astronomy pg. 94-100

• Before Technology, people used stars and
  constellations as a guide or compass.
• Whats a Constellation?
• Patterns of stars in the sky
• Ex Big Dipper

3
If stars form a constellation, does that mean
they are close together?

• No, they can be very far apart
• Big Dipper Star at the end of the handle is
  twice as far from Earth than the rest!

4
Electromagnetic Radiation

• Stars are balls of hot gas that produce light
• Light is a form of Electromagnetic Radiation
• Energy that travels through space in waves

5
Electromagnetic Radiation

• WAVELENGTH
• Distance between the crest of one wave and the
  crest of the next wave
• Some are short and some are long

Visible light has very short wavelengths
6
The Electromagnetic Spectrum

• THE ELECTROMAGNETIC SPECTRUM
• A range of waves including radio waves, infrared
  radiation, visible light, ultraviolet radiation,
  X-rays, and gamma rays.

• SPECTRUM range or sequence

7
The Visible Light Spectrum

• When white light shines through a prism the
  white light is broken apart into colors.

8
The Visible Light Spectrum

• Water Vapor in the sky can act like a prism,
  forming Rainbows.

9
Modern Astronomy

• TELESCOPES scientists can now study more about
  stars.

• What do Astronomers study about stars?
• How much Light they give off
• This helps us learn how far away a star is or how
  big it is.

10
Telescopes

• Collect and focus various types of
  electromagnetic radiation, including visible
  light
• Invented by Galileo in 1609
• Many different types of telescopes

11
Refracting Telescope

• Uses a convex lens to gather a large amount of
  light and focus it onto a small area.
• Uses two lenses eyepiece lens and objective lens

Convex lenses curved and thicker in the center
12
Reflecting Telescope

• Uses a mirror instead of an objective lens.
• All large, modern visible light telescopes are
  reflecting telescopes

13
Reflecting Refracting Telescopes
14
Radio Telescopes

• Detect Radio waves from objects in space.
• Have a curved reflecting surface to focus and
  collect radio waves.

15
The Very Large Array or VLA A Radio Telescope
Observatory
Observatory A place containing one or more
Telescopes.
16
Arecibo Radio TelescopePuerto Rico
17
Space Telescopes Hubble
Space telescopes are attached to satellites and
can collect UV, infared, and X-rays.
18
Spectrograph

• Most large telescopes today have them
• Breaks the light from an object into colors
• Produces a photo of spectrum of colors
• Scientists use these to get info about stars

19
Spectrograph

• Can be used to detect chemical composition and
  temperature of objects in space.

• Chemical
• Elements in stars absorb light at different
  wavelengths
• Shown as dark lines on spectrum
• Temperature
• The amount of energy a star absorbs depends on it
  temperature

20
Section 2Characteristics of Starspg. 103-109
21
Universe vs. Galaxy

• Universe
• All of space, and everything in it
• Contains Billions of Galaxies
• Galaxy
• A giant structure or cluster of Billions of
  stars.
• We live in the Milky Way Galaxy

22
Distance to Stars

• Distances in space are so large, that we cannot
  use regular distance units
• Our nearest Star is Proxima Centauri
• Traveling at the speed of light, it would still
  take you over 4 years to get there!
• The center of our galaxy would take you 25,000
  years to get there!!
• The Galaxy, Andromeda, would take you 2 Million
  years!!

23
Light Years

• LIGHT YEARS- distance light travels in one year
  (9.5 million million km)
• Light travels at 300,000 km per second
• Light from the sun to the earth takes 8 minutes
• Light from Proxima Centauri takes 4.2 years to
  travel, so it is 4.2 light years away

24
Parallax

• The apparent change in position of an object when
  you look at it from different places, or points
  of view, even though it hasnt moved
• Astronomers use parallax to measure distances to
  nearby stars
• Can only measure distances up to 1,000 light years

25
Parallax Shift

• Astronomers look at stars when earth is on one
  side of the sun, and then again when earth is on
  the other side of the sun
• They measure how much the star appeared to move
• This helps scientists calculate how far away a
  star is
• The less it appears to move, the farther away it
  is.

26
Classifying Stars

• How can we classify stars??
• Size
• Temperature
• Brightness

27
Star Sizes

• Super Giant ex. Betelgeuse (almost as big as our
  solar system!)
• Red Giant
• Medium (our Sun)
• White Dwarf (size of Earth)
• Neutron ( 20 km )

28
Stars Sizes
29
Temperature Color

• A stars color reveals its temperature.
• The coolest stars (3,200 degrees Celsius) are
  Reddish in color.
• Hotter stars (5,500 degrees Celsius) appear white
• The Hottest stars (over 10,000 degrees Celsius)
  are Blue

30
MAGNITUDE
TEMPERATURE
31
Brightness of Stars

• Called MAGNITUDE
• Depends on size and temperature
• Photosphere layer of a star that gives off
  light
• How bright it looks from Earth depends on how far
  away it is, and how bright it actually is

32
Two types of Magnitude

• Apparent Magnitude
• Brightness as seen from Earth
• Easily measured using electronic devices
• Does not tell how much light the star actually
  gives off

33
Two Types of Magnitude

• Absolute Magnitude
• Brightness of a star if it were a standard
  distance from Earth
• More complicated accurate must know the
  apparent magnitude and distance from Earth in
  order to calculate

34
If a star looks brighter in the sky from Earth,
then does that mean it gives off more light?

• No, if a smaller, dimmer star is much closer than
  a larger, brighter star, the closer star will
  APPEAR brighter ( Apparent Magnitude) but in
  reality, its not giving off nearly as much light
  (Absolute Magnitude).

35

• Betelgeuse is cool, and doesnt give off much
  light, but is very big.
• Rigel is small, but very hot, so it also gives
  off a lot of light.
• Even though they are different, their Apparent
  Magnitude is about the same.

36
How are Temperature and Magnitude related?

• Scientists Hertzsprung and Russell found a
  pattern when they plotted star temperatures on
  the x-axis, and brightness on the y-axis.
• Called the H-R diagram

37
Hertzsprung-Russell Diagram

• Main Sequence
• Most of the stars form a diagonal line.
• Surface temp. increases, as magnitude increases.

38
Section 3 Lives of Starspg. 112-117

• How long do stars live?
• Star lives occur in stages.
• Stars evolve over Billions of years
• 1st discovered in 1967 a Pulsar
• Object in space emitting regular pulses of radio
  waves.
• Occurs after a Giant star explodes

39
Birth of a Star

• NEBULA
• large amount of gas and dust spread out in a very
  large volume.
• All stars begin as part of a nebula
• PROTOSTAR
• 1st stage of a star
• Forms when gravity pulls the gas dust in a
  nebula together
• when the contracting gas dust become so hot,
  nuclear fusion begins.

40
Lifetime of stars

• How long a star lives depends on how much mass it
  has.
• Smaller-mass stars tend to burn energy more
  slowly, and last longer than Large-mass stars.
• Small mass stars live about 200 billion years
• Medium mass stars (the Sun) live about 10 billion
  years
• Large mass stars live only 10 million years
• (0.01 as long as the sun!)

41
Death of Stars

• Stars eventually run out of fuel
• The center of the star shrinks, while the outer
  part expands.
• They become a Red Giant, or Supergiant
• Depending on its mass, it will become one of the
  three
• White Dwarf
• Neutron Star
• Black Hole

42
White Dwarf

• Small medium size stars
• After the star loses fuel, the outer layer
  expands and drifts away
• The blue/white hot core left behind is called a
  White Dwarf
• About the size of Earth one million times as
  dense as the sun
• No fuel left, just glows faintly from leftover
  energy

43
White Dwarf
White dwarf Sirius-B in x-rays
44
Neutron Star

• Explosion of dying Giant or Supergiant called a
  SUPERNOVA
• Material left behind from an explosion forms a
  Neutron Star
• 3 times the mass of sun, but only about 20 km in
  diameter (the size of a City)

45
Neutron Star
Supernova
46
Black Hole

• The most massive stars (40 x the sun)
• Large mass is left behind after explosion
• Gravity is so strong it pulls the gas inward
• Nothing can escape, not even light
• No form of radiation can escape, so they are hard
  to detect
• Scientists can detect matter from other stars
  being pulled in by a black hole

47
Black Hole
A super-massive black hole has ripped apart a
star and consumed a portion of it, according to
data from ESA and NASA. These results are the
best evidence yet that such a phenomenon, long
predicted by theory, does actually happen.
www.esa.int/export/esaCP
48
Section 4 Star Systems Galaxies
49
Star Systems

• Groups of two or more stars
• More than half of all stars are part of star
  systems
• Our star, the Sun, is NOT part of a star system
• Binary Star two stars
• Ex Alpha Centauri A Alpha Centauri B
• Triple Star three stars

50
Eclipsing Binary

• Sometimes a star in a binary system passes in
  front of the other, and blocks the light from the
  other
• Astronomers may not be able to see the other
  star, but can tell its there because of the
  affect of its gravity on the other star

51
Are there Planets around other Stars??

• 1995 Astronomers observed a star moving back
  and forth very slightly
• They knew it wasnt caused by something with the
  mass of a star, so it must have been a planet
• 2000 astronomers found a planet orbiting a star
  10.5 light years away

52
Types of Galaxies

• Spiral
• Elliptical
• Irregular

Andromeda
53
Spiral Galaxy

• Our Milky Way
• Shaped like a pinwheel

54
Elliptical Galaxy

• Round, Flat Shape
• Very little gas dust between stars
• Few new stars form
• Contain mostly older stars

Virgo Cluster
55
Irregular Galaxy

• No regular shape

56
Famous Galaxies
Siamese Twins
57
Famous Galaxies

Sombrero
58
Famous Galaxies
Polar Ring inner ring of old stars and outer
ring of new stars
59
Our Galaxy The Milky Way
60
Section 5History of the Universe

• The universe is Billions of years old
• Looking at stars is like looking back in time
• Star light can take millions or billions of years
  to reach our planet

61

• By using spectrographs and other instruments to
  measure radiation, astronomers can tell how fast
  a galaxy is moving and whether its moving toward
  or away from us.

62
Are most galaxies moving toward us or away?

• Most Galaxies are moving away from us and each
  other, therefore space in the universe is
  expanding

63
How did the Universe begin?

• BIG BANG THEORY
• States that the universe formed in an enormous
  explosion about 10 15 billion years ago
• In the beginning, the universe was small, dense
  and hot
• Since the Big Bang, it has been expanding

64
(No Transcript)
65
How did our Solar System form?

• About 5 Billion years ago
• Nebula collapsed and started spinning
• Became hot, nuclear fusion started
• The Sun was formed
• Other dust gas formed solid spheres- planets

66
What is the Future of the Universe?

• Could continue to expand
• Stars could run out of fuel and it would be cold
  and dark
• Gravity could pull the galaxies back together
• All of the universe could become a black hole
• WE DONT KNOW!!!