$A$ group of bright and faint stars is called

Venus looks brighter than other planets because

According to the pulsating theory,the expansion and contraction of the universe repeats after every

Which planet is known as the sister of the Earth?

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:

What are the approximate sizes of the observable universe and an atomic nucleus?