The number of stars in our solar system is

Meteors are

Smaller pieces of heavy stones and metals which burn out upon entering the Earth's atmosphere are known as:

There are certain types of stars called variable stars which undergo periodic changes in their light output. If such a star quadruples its light output,how much does its magnitude change?

The temperature of the Earth without the greenhouse effect would be: (in $^{\circ} C$)

When the original mass of a star is greater than $5\, M$ ($M =$ mass of the sun),the death of this star will give rise to: