Astronomy | Astrophysics Answers

Explain what you understand by the apparent magnitude of a star. How is it related
to the brightness of the star? An object A has an apparent magnitude of –5. Another
object B has an apparent magnitude of –10. Calculate the ratio of their brightness

Explain why we expect the gas in elliptical galaxies to be hot.

Define an active galaxy. What is the source of its activity?

Define an active galaxy. What is the source of its activity?

Calculate the half-width of a spectral line of wavelength λ = 550 nm when the
temperature of the gas is 6 × 10^5
K. Assume H atoms to be emitters.

Explain Hubble’s scheme of galaxy classification. Why has this scheme proved
enduring? What class has been assigned to the Milky Way Galaxy?

The average energy of particles in the early phase of the universe, when it was very
hot, was approximately 10 GeV. Calculate the corresponding temperature.

Obtain an expression for the radial velocity of objects in the galaxy as a function of their
galactic longitude.

The mass and radius of a neutron star is 2MΘ and 15 km, respectively. Calculate the
value of gravitational red shift for light of wavelength 6000 Å at a distance of 2 m
from its surface.

Explain the concept of degeneracy pressure. What role does it play in the evolution
of a star after its death?