Astronomy: Chapter 9

Question 1

What is meant by the “period luminosity relation” of the Cepheid Variables, and how can this be used as a distance indicator to the stars?

Answer 1

• period-luminosity relation: the relation between period of pulsation and intrinsic brightness among Cepheid Variable stars.
  
  • leavitt disovered that the brighter stars have a greater “period luminosity relation”. the “period” is related to its brightness. brighter stars=brighter periods.
• massive stars are larger and pulsate slower, lower mass stars are less luminous and pulsate faster.
• shaply was able to find the average distance of a few of the nearest Cepheid and from that their average luminosity. with that, he replaced leavitts apparent magnitudes with absolute magnitudes on the H-R.

Question 2

Draw two labeled sketches of the MIlky Way Galaxy, one as seen from the side, one as seen from the “top”; describe the structure and components of the galaxy.

Answer 2

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Question 2

Draw two labeled sketches of the MIlky Way Galaxy, one as seen from the side, one as seen from the “top”; describe the structure and components of the galaxy.

Answer 2

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Question 3

How is the mass of the Milky way measured, and how does this lead to the concept of dark matter?

Answer 3

To find the mass of the galaxy, you must look at the orbital motions of the stars within the galaxy. every star in the galaxy follows an orbit around the center of mass of the galaxy. in the disk, the stars follow parallel circular orbits, and astronomers say the disk of the galaxy rotates. That rotation can allow an estimate of the mass in the galaxy.

Question 3

How is the mass of the Milky way measured, and how does this lead to the concept of dark matter?

Answer 3

To find the mass of the galaxy, you must look at the orbital motions of the stars within the galaxy. every star in the galaxy follows an orbit around the center of mass of the galaxy. in the disk, the stars follow parallel circular orbits, and astronomers say the disk of the galaxy rotates. That rotation can allow an estimate of the mass in the galaxy.

Question 4

How are the spiral arms of the Milky Way detected, and what is their nature?

Answer 4

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Question 4

How are the spiral arms of the Milky Way detected, and what is their nature?

Answer 4

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Question 5

Discuss the reason for the differences between population I and population II stars.

Answer 5

• Population I
  
  • Heavy elements
  • located in the disk
  • Born from heavy metals
  • Our sun
• Population II
  
  • No heavy metals
  • located in the Halo
  • Born from non-heavy metals
  • stars are older
  • formed from a supernova.

Question 5

Discuss the reason for the differences between population I and population II stars.

Answer 5

• Population I
  
  • Heavy elements
  • located in the disk
  • Born from heavy metals
  • Our sun
• Population II
  
  • No heavy metals
  • located in the Halo
  • Born from non-heavy metals
  • stars are older
  • formed from a supernova.

Question 6

Describe the characteristics of and differences between open and globular clusters.

Answer 6

• Globular
  
  • spherical
  • up to a million (10^6) stars
  • ancient
  • red dwarfs
  • old halo
• Open
  
  • shapeless
  • 10 - 1000 stars
  • young
  • red and blue stars
  • disk

Question 6

Describe the characteristics of and differences between open and globular clusters.

Answer 6

• Globular
  
  • spherical
  • up to a million (10^6) stars
  • ancient
  • red dwarfs
  • old halo
• Open
  
  • shapeless
  • 10 - 1000 stars
  • young
  • red and blue stars
  • disk

Question 7

what is the observational evidence that something strange is happening in the nucleus of our Galaxy, and what is the probable explanation?

Answer 7

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Question 7

what is the observational evidence that something strange is happening in the nucleus of our Galaxy, and what is the probable explanation?

Answer 7

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