Hubble's law is related to:

$A$ Black Hole is:

The magnitudes of two stars $A$ and $B$ are $2.5$ and $-5$ respectively. The brightness ratio of $\frac{B}{A}$ is

If the axis of rotation of the earth were extended into space,then it would pass close to

The galaxy in which we live is:

The tail of the comet is due to