Question

1. a star is identified as belonging to the supergiants category. what are the general characteristics of this star according to the h - r diagram? (1) high temperature and high luminosity (2) low temperature and low luminosity (3) low temperature and high luminosity (4) high temperature and low luminosity 9) based on the information presented, what is the primary factor that determines a stars lifetime? (1) its brightness and temperature (2) its position in the galaxy (3) its spectral class only (4) its color and distance from earth 10) what is the primary information used to place a star on the h - r diagram? (1) its distance from earth and its apparent brightness (2) its mass and its radius (3) its surface temperature and its true brightness (4) its age and chemical composition

Explanation:

• Question 8: On the H - R diagram, supergiants are large stars. According to the Stefan - Boltzmann law \(L = 4\pi R^{2}\sigma T^{4}\) (where \(L\) is luminosity, \(R\) is radius, \(\sigma\) is the Stefan - Boltzmann constant, and \(T\) is temperature), although some supergiants can have relatively low surface temperatures (compared to main - sequence stars of the same luminosity), their large radii give them high luminosities.
• Question 9: The lifetime of a star is mainly determined by its mass. More massive stars have higher core temperatures and pressures, which cause them to fuse hydrogen (and other elements) at a much faster rate. However, among the given options, brightness (related to luminosity) and temperature (related to the rate of nuclear fusion) are factors that can be associated with the lifetime (since higher luminosity and temperature imply faster nuclear reactions in a general sense for stars of similar types).
• Question 10: The H - R diagram (Hertzsprung - Russell diagram) plots stars based on their surface temperature (or spectral class, which is related to temperature) on the x - axis and their absolute (true) brightness (luminosity) on the y - axis.

Answer:

• 8) (3) low temperature and high luminosity
• 9) (1) its brightness and temperature
• 10) (3) its surface temperature and its true brightness