$A$ bright star is indicated to have a brightness magnitude of $-5$ compared to a star of brightness zero magnitude. It means that this star,compared to the reference star of zero brightness,is:

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

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

The tail of a comet points

The farthest objects in our Universe discovered by modern astronomers are so distant that light emitted by them takes billions of years to reach the Earth. These objects (known as quasars) have many puzzling features,which have not yet been satisfactorily explained. What is the distance in $km$ of a quasar from which light takes $3.0$ billion years to reach us?

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