Astronomy | Astrophysics Answers

Distinguish between elliptical, spiral and elliptical galaxies and give one example of
each type of galaxy.

How long will a 5MΘ star burn hydrogen as fuel, given that the Sun will do so for
about 1010 years?

A white dwarf star has a mass of 1030 kg. Its luminosity is 1024 Js−1. Calculate how
long it can survive with its present luminosity if its internal temperature is 107 K.

A star has surface temperature of 25000 K. Which lines would be prominent in its
spectrum and why?

The mean distance of Mars from the Earth is 0.5 A.U. and its orbital period is 687
days. Calculate the orbital period of Jupiter given that its mean distance from the
Earth is 4 A.U.

Explain how sunspots survive for so long even though they are surrounded by hotter
matter.

A main sequence star has mass 2×1031 kg and radius 3×109
m. Obtain an estimate of
the average temperature throughout the star.

Explain the following terms with the help of a diagram, wherever needed celestial
sphere, zenith, circumpolar stars, diurnal circle, resolving power of a telescope.

After about 1 billion year, the radius of a star is expected to increase by 100 times its
present radius. If its temperature becomes half of what it is today, determine the
change in its absolute magnitude.

The distance modulus of a star is − 0.1. At what distance is it from the earth?