The following sentences form a paragraph. The last sentence of the paragraph is given. The rest of the sentences are numbered as P, Q, R, S and T. These parts are not given in their proper order. Read the sentences and choose the alternative that arranges them in correct order.

P. Its small companion is the subject of a great deal of study, as well. 

Q. It shows a classic spiral shape and a curious little companion that appears to be attached to one of the spiral arms.

R. The Whirlpool also has a fascinating structure, with its spiral arms and central black hole region. 

S. It is showing astronomers how galaxies interact with each other and how stars form within them. 

T. The Whirlpool is a neighboring galaxy to the Milky Way.

For amateur observers, the Whirlpool is a joy to observe.