Question

i. What is a galaxy?
ii. How are spiral galaxies different from elliptical galaxies?
ini. What is the percentage of irregular galaxies in the Universe?
iv. What is common between the spiral galaxies and irregular galaxies:
v. The spiral galaxies look bright because they
(a) get the sunrays directly reflected on their surfaces
(b) contain the younger stars which shine brightly
(c) emit a fluorescent gas which makes them bright
(d) are closer to the earth​

Answer 1

i)A galaxy is a huge collection of gas, dust, and billions of stars and their solar systems, all held together by gravity. We live on a planet called Earth that is part of our solar system

ii)While spiral galaxies are bright, elliptical galaxies are dim. Spiral galaxies are hotbeds of star formation, but elliptical galaxies aren't nearly as prolific because they contain less gas and dust, which means fewer new (and brighter) stars are born.

iii)5 percent . An estimated 20 percent of known galaxies have a lenticular form, 15 percent are elliptical and only about 5 percent are irregular.

iv)The bulge and halo consist mainly of older stars, where spiral arms have more gas, dust and younger stars. ... They have a bulge and halo, like spiral galaxies, but don't have the flat disk of stars. The stars in ellipticals tend to be older. Irregular galaxies have no identifiable shape or structure to them.

v)option B)