Assuming you mean the plant and not the universe, its an annual, grown for its bright, daisy like flowers and feathery foliage. Easily grown from seed, or is available in small pots from garden centres mid to late May. Dies in the autumn, or when the frosts start.
There are other varieties of Cosmos available which are perennial in other countries, but will not withstand our cold winters. One has dark maroon flowers which smell of chocolate - again, sold (expensive) at garden centres.

a beautiful place surrounded by stars and other heavenly bodies 8-)