1. Stars and Galaxies
Chapter 26

2. 26.1 Observing the Universe
Constellations
In Greek mythology, pattern clusters of stars were given names and even stories. They classified these as constellations.

3. Distance (in light-years)
Closest stars to us
Star
Distance (in light-years)
Apparent Magnitude
Proxima Centauri (in Centaurus)
4.2
+11.0
Alpha Centauri A and B (in Centaurus)
4.3
-0.3
Barnard's Star (in Ophiuchus)
6.0
+9.5
Wolf 359 (in Leo)
7.7
+13.5
Lalande (in Ursa Major)
8.1
+7.5
Sirius A
8.6
-1.46
Sirius B (in Canis Major)
-xx
Luyten 726-8
8.4
+12.5 xx
UV Ceti (in Cetus)
Luyten (in )
Ross 154
9.4
+10.5
Ross 248
10.4
+12.3
Epsilon Eridani (in Eridanus)
10.8
+3.7
Ross 128
10.9
+11.1

4. Orion

5. Spectroscope Breaks light into a spectrum like prisms.
Light from any element gives a unique spectrum through a spectroscope.
This spectrum of colors produced by the spectroscope is called a spectrogram .
Help study atmosphere gases present on stars, galaxies, planets or moons.

6. Spectrograms

7. Telescope: Three Types
Optical Telescopes use light
Refracting Telescopes use lenses
Reflecting Telescopes use mirrors
Earth’s atmosphere can make objects appear blurry so we put the Hubble Space telescope into orbit above the atmosphere.
Radio Telescopes use radio waves
New telescopes are Active and Adaptive.
Active uses computers to correct problems
Adaptive use lasers to adjust for air effects

8. Refracting Telescope

9. Convex Lens

10. Refracting Telescope

11. Reflecting Telescope

12. Another Reflecting Telescope

13. Hubble Space Telescope

14. Radio Telescope Each star produces unique radio waves.
These can be detected during the day and pass easily through a cloudy atmosphere.
Radio telescopes collect and amplify radio waves.
Radio waves have long wavelengths so the radio telescopes must be very large and dish-shaped.
Sometimes many of them are arranged in a group or array.

15. Radio Telescope

16. World’s Largest Radio Telescope

17. 26.1 Universe Analysis: Date_____ Name___________________ Hr__
Copy questions and answer in complete sentences.
Define Constellation, and name one.
Define Refracting telescope.
Define Reflecting telescope.
How do Radio telescopes work?
Why do we use Radio telescopes?

18. 26.2 Evolution of Stars

19. 26.2 Stars
Star: Nebula cloud condenses by gravity and heats up: 1 million K is a protostar (emits heat), then at 10 million K hydrogen fuses to form helium and a new star (emits heat and light).
Parallax: apparent shift in position of an object seen from 2 different points not on a straight line
Nebula: large cloud of gas, ice and dust in space.
Fusion: when two or more elements combine to form one new element after heat and pressure.

20. Nebula

21. Nebula

22. Classifying Stars
Hertsprung-Russell (HR) Diagram compares surface temperature and luminosity OR absolute magnitude (energy and brightness)
Star colors from hottest to coolest: Blue, White, Yellow, Orange, Red, & Black.

23. H-R diagram

25. Main Sequence
Main Sequence: 90% of stars fall on the HR line from upper left to lower right comparing magnitude and temperature.
Nuclear fusion begins inside a protostar once enough pressure builds.
H + H = He, producing heat and light
A main sequence star is born and lasts for billions of years.

26. The Pleiades Star Cluster

27. Red Giant Star
An average size Main Sequence star eventually uses up its hydrogen
Begins to fuse heavier elements
This makes the star expand
RED GIANT star is born!
Large stars with cooler temperatures

28. A Red Giant From Orion End of H fusion - red giant stage
Betelguese - see

29. Polaris: The North Star

30. Next stage depends on mass
If the original main sequence star is average mass, it will take the following path.
Red giant will slowly lose its outer layers. The star is losing its equilibrium.
Star loses mass until it collapses and turns into a white dwarf.

31. Red Giants Losing Outer Layers
After Helium exhausted, outer layers of star expelled
Planetary Nebulae
Planetary nebula - after He consumed, core collapses again. Outer atmosphere expelled, and then ionized (I.e. glows) by the hot remaining core
From Left to Right:
Ring Nebula - true colors, representing different elements. helium (blue), oxygen (green), and nitrogen (red).
NGC The central star of NGC 2440 is one of the hottest known, with surface temperature near 200,000 degrees Celsius. The complex structure of the surrounding nebula suggests to some astronomers that there have been periodic oppositely directed outflows from the central star, but in the case of NGC 2440 these outflows have been episodic, and in different directions during each episode. The nebula is also rich in clouds of dust, some of which form long, dark streaks pointing away from the central star. In addition to the bright nebula, which glows because of fluorescence due to ultraviolet radiation from the hot star, NGC 2440 is surrounded by a much larger cloud of cooler gas which is invisible in ordinary light but can be detected with infrared telescopes. NGC 2440 lies about 4,000 light-years from Earth in the direction of the constellation Puppis.
NGC colors represent temperatures. Filaments made of dust condense out from the cooling gas. These filaments are rich in carbon
[Images from Hubble Heritage:

32. White Dwarfs

33. Other Dwarf Stars
White dwarfs run out of fuel and become red, then black dwarf stars.
Black dwarf stars no longer produce light.
RIP
These brown/black dwarf stars do not exist yet because they take trillions of years to form.

34. What about large mass stars?
Main sequence stars with large mass will still turn into red giants.
Eventually, the red giant will continue to grow into…..
SUPERGIANTS!!!!

36. Distant Supergiant

37. Supergiant

38. Supergiants
Supergiants grow even larger due to nuclear fusion of heavier elements.
Eventually, the element iron will be fused together in the core.
This makes the core unstable!

39. Danger! Once iron makes the core unstable, a SUPERNOVA can occur.
A supernova is a star explosion which usually creates bright light.

41. Supernova !
SN1987A before and after image from Anglo-Australian Observatory. It’s in the LMC, 160,000 light-years distant.
When fusion process no longer produces energy to support the star, the core of the star collapses. With nothing to stop it, the atoms are crushed together, and the infalling material bounces off the superdense core, causing the explosion.
A supernova produces 1040 erg/s (a million times more than the sun). The supernova disperses the elements it has created. In addition, the energy of the explosion creates elements heavier than iron.

42. Supernova Remnants

43. After the supernova
After the supernova, 3 things can form: new star, neutrons star, or black hole.
Neutron stars contain only neutrons.
Neutron stars are tiny but one spoonful of this star has the same mass as Earth!
If a neutron star produces radio waves we call it a pulsar.

44. Neutron Star (yes, the tiny dot)

45. Thermal Image of Neutron Star

46. Size of Neutron and White Dwarf Stars if placed in Grand Canyon

47. Supernova Remnants Optical X-ray
Cas A is 300 years old. The remnant is about 10 light-years in diameter, and 10,000 light-years away.
X-ray: outer shock wave is from the initial supernova explosion ripping through the interstellar medium at 10 million miles per hour. Temperatures may reach 50 million degrees. The inner shock is the ejecta from the SN heating up the circumstellar shell, heating it to 10 million degrees
The optical image of Cas A shows matter with a temperature of about ten thousand degrees. Some of these wisps contain high concentrations of heavy elements and are thought to be dense clumps of ejected stellar material.
Cas A x-ray and optical images from

48. Black Holes
After a supernova, if a neutron star doesn’t form then a black hole forms.
This is a dense area with intense gravity, so intense that not even light can escape it.
Begins to force all nearby matter into it.
This dense area is called a singularity.

49. Black holes
Black holes emit light as they take in matter due to the material traveling at high speed, which creates friction.
Black holes also emit X-rays
Black holes that exist in the center of galaxies are called QUASARS.

50. Black hole
Diagram

52. Q u a s r

53. Name the Stars you see!

54. Twinkle, Twinkle, Little Star ...
Hubble Heritage image of Sagittarius Star field. Note that along the horizontal axis, the image is 13.3 light-years across.
Ask audience what they notice by looking at this image. Hopefully they will notice the different colors. You can then ask them what the different colors mean [different temperatures]
Image from

55. Vega / Sirius

56. Binary Stars
A system of two stars in which one star revolves around the other, or both revolve around a common center.
In fact, 85% of the stars in the Milky Way galaxy are not single stars, like the Sun, but multiple star systems, binaries, or triplets.

57. Binary Stars

58. Parts of a Star Stars use nuclear fusion to produce heat and light.
This combines 2 atoms to create a different element.
If hydrogen with atomic number 1 is added to another hydrogen, what does that produce (equal)?

60. New Elements Formed H + H = 1 + 1 = Helium (2) H + He = 1 + 2 =
Lithium (3)
H + Li = =
Beryllium (4)

61. Where does the heat go? Nuclear fusion occurs in the core of stars.
Heat then moves away from the core and heads toward the surface of the sun.
Radiative Zone: heat is transferred by radiation
Convective Zone: heat transferred by convection
Zone location depends on the mass of the star

62. Outer Layers of the Sun On top of the “zone” area is the PHOTOSPHERE
The photosphere creates light we can see. The surface of the Sun is marked by granules (or marks) caused by convection in the photosphere or outer layer of the Sun.
On top of the photosphere is the CHROMOSPHERE.
The chromosphere appears red or orange.

63. Photosphere and Chromosphere

65. Other parts of the sun
Corona: layer that looks like a halo extending into space
The corona is visible during solar eclipses.
Solar wind, charged particles from the sun, is released from the corona.

66. Corona in Visible Light

67. Corona again

68. Sunspots Sunspot: dark, cool region on the sun.
Every 11 years, the sun produces many sunspots.
Sunspots form from overlapping magnetic fields.

69. Sunspot Close-up

71. Sunspots

73. Sunspot Issues Sunspots can produce PROMINENCES.
A prominence is a loop of gas that connects sunspots together.

74. Prominence Close-up

75. Granulation and Prominence

76. When Prominences Connect
If several prominences connect, they create explosions called SOLAR FLARE
Solar flares produce C.M.E.’s or Coronal Mass Ejections.
CMEs send millions of solar wind particles toward us & are dangerous!

77. Flares

78. Flare Close-up

79. Solar Flares and C.M.E.

82. Name the layers of the sun!

83. 26.2 Star Analysis: Date_________ Name__________________ Hr___
Copy questions and answer in complete sentences
Define a) Nebula, b) Protostar, and c) Star.
What is the H-R Diagram?
Describe how a star becomes a red giant.
A) Draw, b) label, & c) color the parts of the Sun.

84. Galaxies and The Milky Way
Chapter 26,
Section 3 and 4

85. Big Bang Theory Universe created with an explosion
Explains why space and matter is still expanding away from each other.
Our galaxy is part of the LOCAL GROUP, which contains 45 galaxies.

86. Galaxies
A galaxy is a large group of stars, gas, and dust held together by gravity.
Our sun is one of 400 billion stars in the Milky Way Galaxy.

87. Types of Galaxies Spiral Barred Spiral Elliptical Irregular Peculiar
disk-like appearance with arms of stars and dust forming a spiral pattern
similar to spirals but with a bright bar of stars and gas through the center; arms extend outward
elliptically-shaped, with less gas and dust than spirals; no disk or “arms”
distorted form of one of the above types, often due to collision with another galaxy or similar catastrophic event
Barred Spiral
neither elliptical nor spiral in shape; gas and dust as in spirals but no defined “arms”
Elliptical
Irregular
Peculiar

88. Galaxies
Elliptical galaxies are football shaped and the most common in the universe.
Elliptical galaxies may also be the largest, with some being 9 million light years across!
The Milky Way is a barred spiral galaxy.

89. Milky Way Galaxy

90. Milky Way Galaxy

91. Our Sun is on the edge of one spiral and 26,000 Light Years to the Center. Milky Way is 100,000 Light Years long and about 1,000 Light Years thick.

92. Andromeda Galaxy Spiral 2.6 Million Light Years Away

93. Magellan Cloud: Irregular 60,000 L.Y.

94. Studying Galaxies
The Doppler Effect is used to study the motion of galaxies.
The wavelength changes from speed and direction of a moving object, similar to how cars sound different as they approach or speed away.
Close Galaxies appear blue (short wavelength) moving towards us.

95. Hubble Red Shift
Galaxies outside of the local group show a Hubble Red Shift.
These distant objects have longer wavelengths of light and appear RED as they move away from us!

96. What kind of galaxy am I?

110. When Galaxies Collide!

116. Clusters of Galaxies

121. Hubble Telescope View of Universe

122. What is the Universe Made of?
Gravity is related to the amount of mass in the universe, but scientists say there is far too little mass for the amount of gravity we believe is here.
So the idea of DARK MATTER is born.
Dark Matter must be causing the large gravitational force affecting galaxies.

123. Dark Energy
BUT the universe is EXPANDING and ACCELERATING due to Dark Energy.
Gravity was keeping the escape of matter slow, but since matter is now so far apart in space and expanding quicker, Dark Energy must be greater than Gravity.

124. Cosmic Background Radiation
One way to measure the age of the universe is to use temperatures found in microwaves in outer space.
Current estimate is 13.7 billion years.

126. 26-3 Universe/Galaxy Review
Over 40 billion galaxies in the universe.
Milky Way, Andromeda and about 43 other galaxies are in the Local Group.
The Clouds of Magellan and the Sagittarius Dwarf are examples of Irregular Galaxies.

127. 26-3 Universe/Galaxy Review 2
The Milky Way is a Barred Spiral and Andromeda is a Spiral Galaxy.
A theory of how galaxies form is that they came from fluctuations in the density of primordial matter.
Milky Way has 400 billion stars, is 100,000 LY across & 1000 LY thick.

128. 26-4 Cosmology Review Cosmology: study universe’s beginning
3 Theories of Cosmology:
Big Bang: rapid expansion space/matter
Steady State: always existed/always will
Oscillating Model: expands & contracts

129. 26-4 Cosmology Review 2 Universe began 13.7 billion years ago
The universe is still expanding.
We know because of Hubble Red Shift.
Doppler Effect (Shift): A wavelength-change in a moving source.
If wave source is moving away, the wavelength expands (red shift).

130. 26-4 Cosmology Review 3
The universe is made of regular matter, dark matter, and dark energy.
The cause of clumping of galaxies into clusters may be from dark matter.
The increasing expansion of the universe may be caused by dark energy.

131. 26.3-4 Galaxies Analysis: Date____ Name__________________ Hr___
Compare and Contrast the 5 Galaxy Types:
Fold your paper into 4 equal sections.
In Section 1 write a paragraph about Similarities.
In Section 2 write a paragraph about Differences
In Sections 3, 4, 5, 6, 7 Title each Galaxy type and Describe it, then Draw and Color it.
In Section 8 write about what might happen if Andromeda and Milky Way galaxies collide.