The national flag of Brazil is a blue disc depicting a starry sky (which includes the Southern Cross) spanned by a curved band inscribed with the national motto "Ordem e Progresso" ("Order and Progress"), within a yellow rhombus, on a green field. It was officially adopted on 19 November 1889 — four days after the Proclamation of the Republic, to replace the flag of the Empire of Brazil. Each star, corresponding to a Brazilian Federal Unit, is sized in proportion relative to its geographic size, and, according to Brazilian Law, the flag must be updated in case of the creation or extinction of a state. At the time the flag was first adopted in 1889, it had 21 stars. It then received one more star in 1960 (representing the state of Guanabara), then another in 1968 (representing Acre), and finally four more stars in 1992 (representing Amapá, Roraima, Rondônia, and Tocantins), totaling 27 stars in its current version.

Source: Wikipedia