Astronomy | Astrophysics Answers

Calculate the magnitude of the faintest object that can be detected by an optical
telescope of diameter 5.0 m

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

Sketch the celestial equator, horizon, observer’s meridian and show the zenith and
nadir on the celestial sphere for an observer at latitude 30° N.

1. a) 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. (1+1+3) b) Sketch the celestial equator, horizon, observer’s meridian and show the zenith and nadir on the celestial sphere for an observer at latitude 30° N.

Calculate the half-width of a spectral line of wavelength λ = 550 nm when the
temperature of the gas is 6 × 105
K. Assume H atoms to be emitters.

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

Write down the condition under which a large molecular cloud collapses to give rise to new stars. Calculate the time of free fall of an HI cloud of density (10)6 particles/(m)3.

The estimated lifetime of the Sun on the main sequence is ~ 1010 years. Calculate the main sequence lifetime of stars of masses (i) 100 MΘ and (ii) 5 MΘ.

What is the difference between the HII region and HI region of the interstellar medium? Explain the process involved in the detection of HI region in the ISM.

The absolute visual magnitude of a star is 6.5 and for its temperature, the bolometric correction is − 0.3. Calculate the absolute bolometric magnitude and the luminosity of the star.