Which one of the following is known as $Saptarishi$?

The percentage of the Sun's total energy that reaches the Earth's surface is:

The length of the Milky Way is .......... light years.

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?

$CO_2$ gas is found in which of the following pairs of planets?

Describe the Ptolemaic model for planetary motion.