$A$ Black Hole is:

Venus looks brighter than other stars because

How does the red shift confirm that the universe is expanding?

In our solar system,there is one sun and

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:

The angle of maximum elongation for Venus is $47^\circ$. The distance of Venus from the Sun in $AU$ is .......