Astronomy: Chapter 10

Question 1

What is the observational evidence that some so-called “nebulae” are actually entire galaxies far outside our own galaxy?

Answer 1

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Question 2

Describe the chief method for determining the masses of the galaxies, and what does this tell us about dark matter?

Answer 2

• Rotation Curve Method: Requires
  
  • The true size of the orbits of stars or gas clouds within a galaxy, which in turn requires knowing the distance of that galaxy.
  • the orbital speeds of the stars or gas clouds, measured from the doppler shifts of their spectral lines.
• Using keplers third law, we can find the mass of the part of the galaxy contained within the star orbit with measured size and speed.
• 95% of matter is dark matter.

Question 3

Describe the factors involved in galactic formation, including the role of collisions between galaxies.

Answer 3

• Elliptical galaxies appear to be the product of galaxy mergers, which triggered star formation that used gas and dust.
• in the beginning, there were proto-galaxies. These proto-galaxies collided to create spiral galaxies. spiral galaxies collided to create elliptical galaxies.
• galaxies collide frequently. When they collide, gases compress with each other to form new gasses.

Question 4

Be able to identify a galaxy by its shape, according to the Hubble telescope.

Answer 4

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Question 5

Describe the observational evidence for the “dark matter” and discuss the most likely candidates for what it consists of.

Answer 5

The measured masses of galaxies amount to 10-100 times more mass than we can see. evidence indicates that there is 10-100 times more dark matter than visible matter in galaxies. Dark matter remains to be unresolved. Observations of galaxies and clusters of galaxies reveal that 90-95 percent of dark matter in the universe is dark matter.

Question 6

State in your own words what the Hubble law really says and what its implications are concerning the expansion of the universe.

Answer 6

Hubble law: velocity of a galaxy is proportional to its distance.
Farther = faster.

Question 7

Compare and contrast elliptical galaxies and spiral galaxies.

Answer 7

• Elliptical
  
  • More common
  • few young stars.
  • most luminous stars are red giants.
  • no blue giants.
  • Red tint
  • no visible gas or dust.
• Spiral
  
  • spiral and flat
  • smaller range of size.
  • ancient red dwarf and blue giants
  • hot bright stars, constantly luminous, easy to see.
  • blue tint.
  • contains gas and dust.

Question 8

Describe the different types of active galaxies, and the mechanisms proposed to explain their energy output and other characteristics.

Answer 8

• Active galaxy: a galaxy whose center emits large amounts of excess energy, often in the form of radio emission. active galaxies have massive black holes in their centers into which matter is flowing.
• Radio Galaxy: a galaxy that is a strong source of radio waves.
• Seyfert Galaxies: an other wise normal spiral galaxy with an unusually bright, small core that fluctuates in brightness and a dim disk.

Question 8

Briefly relate the story of the discovery of quasars.

Answer 8

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Question 9

Discuss the controversy that originally surrounded quasars.

Answer 9

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Question 10

Describe the current explanation of quasars and their energy sources.

Answer 10

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Question 11

Briefly relate the story of the discovery of quasars.

Answer 11

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Question 12

Discuss the controversy that originally surrounded quasars.

Answer 12

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Question 13

Describe the current explanation of quasars and their energy sources.

Answer 13

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