Chapter 5, Problem 1HRP

To determine

The spectral type, temperature, absolute magnitude number, and luminosity of Star A.

Answer to Problem 1HRP

The star A is of spectral type B, having temperature in the range of $17000\text{K}-18000\text{K}$ . The star A has absolute magnitude of $0\text{to}\left(-1\right)$ and luminosity of star A is 100 solar units.

Explanation of Solution

H-R diagrams are plots of luminosities versus surface temperature and by comparing luminosity that is how dim the star looks, scientists calculate how far the star is.

Star is classified on the basis of spectral characteristics. There are seven major spectral types OBAFGKM is the spectral sequence. Here, O types are the hottest stars and M is the coolest. Sun lies in the spectral type G₂.

Absolute magnitude depends on luminosity and distance of star. Absolute magnitude is the measure of luminosity of star and is in inverse relation with it. It means, the star of lower magnitude is more luminous than star of higher magnitude.

Luminosity is the total energy emitted by the star per second. It depends on the temperature and radius of the star. It is directly proportional to the square of radius and fourth power of temperature of star.

1. a) Spectral type: B
2. b) Temperature: $17000\text{K}-18000\text{K}$

      c) Absolute magnitude: $0\text{to}\left(-1\right)$

      d) Luminosity: 100 solar units

Conclusion:

Thus, the star A is of spectral type B, having temperature in the range of $17000\text{K}-18000\text{K}$ . The star A has absolute magnitude of $0\text{to}\left(-1\right)$ and luminosity of star A is 100 solar units.