Which one of the following planets has the longest day?

Suppose the Sun was located at the position occupied by the nearest star,say,Alpha Centauri,$4$ light-years away. By what factor would the solar radiation received per second per unit area decrease?

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

$A$ galaxy is observed to be moving with a velocity of $8600 \ km \ s^{-1}$. If it is at a distance of $430$ million light-years from us,the Hubble constant and the corresponding age of the universe are respectively:

The image shows a diagram of the solar system. Which of the following planets is known as the 'Red Planet'?

According to modern astronomers,into how many constellations is the whole sky divided?