The ______in the Earth's atmosphere protects living organisms from the harmful ultraviolet radiations of the Sun.

The earth was formed _______ years ago.

The distance from the Sun, presence of water, oxygen and atmosphere are the factors that make life possible on Earth, hence it is called as____.

The first form of living organism on earth was the _______.

_________absorbs infra-red light of the sun and increases the temperature.

The outer core is composed mainly of ______ while the inner core is almost entirely composed of iron.

Silicon, aluminium and magnesium are the chief elements of the _________.

Moon is the Earth's only ______ and our closest celestial neighbour.

The Red planet is ______.

______ rotates faster than any other planet, completing one rotation in less than 10 hours.

_____are a group of small bodies made up of rocks and metals which revolve around the sun.

The other name for asteroid is_____.

If the meteors strike the surface of the Earth, they are called as ______.

Small pieces of space debris that are on a collision course with the Earth are called _____.

Asteroid ______was discovered in an orbit between the orbits of Saturn and Uranus.

Comets are made up of frozen gases like water, ammonia, _____and carbon dioxide.

A _____ is a collection of large number of rocky and metallic particles orbiting around the sun, in an elliptical orbit.

The ________ is the closest star to the Earth after the Sun.

The dense, contracting gaseous mass of cloud is called_____.

____is a stage of the life cycle of the star after red-giant phase.

Brightness of the star depends on _____ and the total energy emitted per second.

The life span of a star depends upon the amount of ______ it had at its birth and its consumption rate.

______ is an explosion of a star with the simultaneous release of tremendous amount of energy.

If a ______star spins, it emits radio waves. It is called a Pulsar.

Ursa major (Great Bear) constellation is also known as the _____.