9.2 Classification of stars

• The H-R diagram is a fundamental tool used to classify and understand the properties of stars
• What insights does the position of a star on the H-R diagram provide?

  Mass, size, age, evolution
• Order the spectral types of stars from hottest to coolest:

  1️⃣ O

  2️⃣ B

  3️⃣ A

  4️⃣ F

  5️⃣ G

  6️⃣ K

  7️⃣ M
• The Sun is an example of a G-type star.
• What is the primary characteristic used to classify stars into spectral types?

  Surface temperature
• What is the color of a star classified as type O?

  Blue
• Arrange the spectral types in order from hottest to coolest:

  1️⃣ O

  2️⃣ B

  3️⃣ A

  4️⃣ F

  5️⃣ G

  6️⃣ K

  7️⃣ M
• Stars on the main sequence exhibit a positive correlation between luminosity and surface temperature
• Giant stars have high luminosity and low surface temperature.


  True
• Arrange the main regions on the H-R diagram based on decreasing luminosity:

  1️⃣ Giant stars

  2️⃣ Main Sequence

  3️⃣ Dwarf stars
• What is the approximate surface temperature of an M-type star?

  2,400 - 3,700 K
• Stars are classified into spectral types based on their surface temperature
• Match the spectral type with its corresponding color:

  O ↔️ Blue

  G ↔️ Yellow

  M ↔️ Red

  F ↔️ Yellowish-white
• What are the units of luminosity?

  Watts
• What does the Hertzsprung-Russell (H-R) diagram plot?

  Luminosity vs. surface temperature
• The position of a star on the H-R diagram reveals its mass, size, age, and stage of evolution.

  True
• Giant stars have high luminosity and low surface temperature.

  True
• What are the seven primary spectral types of stars based on their spectra?

  O, B, A, F, G, K, M
• What is the primary factor used to classify stars into spectral types?

  Surface temperature
• What is the Hertzsprung-Russell (H-R) diagram a plot of?

  Luminosity vs. temperature
• Match the star type with its characteristics:

  Giant stars ↔️ High luminosity, low temperature

  Dwarf stars ↔️ Low luminosity, high temperature
• Giant stars are located in the upper-right of the H-R diagram


  True
• Match the spectral type with its surface temperature range:

  O ↔️ 30,000 - 60,000 K

  B ↔️ 10,000 - 30,000 K

  A ↔️ 7,500 - 10,000 K

  F ↔️ 6,000 - 7,500 K

  G ↔️ 5,200 - 6,000 K

  K ↔️ 3,700 - 5,200 K

  M ↔️ 2,400 - 3,700 K
• Which spectral type includes the coolest stars?

  M
• Most stars on the H-R diagram lie along the main sequence.


  True
• What key properties of a star can be determined using its position on the H-R diagram?

  Mass, size, age
• Stars on the main sequence exhibit a positive correlation between luminosity and surface temperature
• Match the spectral type with its surface temperature range and color:

  O ↔️ 30,000 - 60,000 K, Blue

  B ↔️ 10,000 - 30,000 K, Blue-white

  A ↔️ 7,500 - 10,000 K, White

  F ↔️ 6,000 - 7,500 K, Yellowish-white

  G ↔️ 5,200 - 6,000 K, Yellow

  K ↔️ 3,700 - 5,200 K, Orange

  M ↔️ 2,400 - 3,700 K, Red
• Our Sun is an example of a star classified as type G
• What is the definition of luminosity?

  Total energy emitted per time
• Absolute magnitude is a measure of a star's intrinsic brightness independent of its distance.


  True
• Match the region on the H-R diagram with its description:

  Main Sequence ↔️ Stars actively fusing hydrogen

  Giants ↔️ High luminosity, low temperature

  Dwarfs ↔️ Low luminosity, high temperature
• The Main Sequence on the H-R diagram shows a positive correlation between luminosity and surface temperature
• Order the spectral types from hottest to coolest based on surface temperature:

  1️⃣ O

  2️⃣ B

  3️⃣ A

  4️⃣ F

  5️⃣ G

  6️⃣ K

  7️⃣ M
• Match each spectral type with its surface temperature range:

  O ↔️ 30,000 - 60,000 K

  B ↔️ 10,000 - 30,000 K

  A ↔️ 7,500 - 10,000 K

  F ↔️ 6,000 - 7,500 K
• What is luminosity in the context of stars?

  Total energy emitted per time
• Most stars on the H-R diagram lie along the main sequence.
• Where are giant stars located on the H-R diagram?

  Upper-right corner
• Stars on the main sequence show a positive correlation between luminosity and surface temperature

  True
• The main sequence of the H-R diagram shows a positive correlation between luminosity and surface temperature