The first Republican Brazilian flag was adopted in November 19, 1889. It was idealized by Raimundo Teixeira Mendes, with the collaboration of Miguel Lemos and of Professor Manuel Pereira Reis. The design was executed by Décio Vilares.
It is a green flag with a large yellow rhombus located in the center. Within the rhombus there is a blue circle, with white stars of five different sizes and a white band running through it. The motto "Ordem e Progresso" is inscribed in the band.
Symbology
It's often said that the Brazil's national colors (green and yellow) is a representation of the country's natural richness. Green would represent the forest exuberance of the Amazon Rainforest, the Atlantic Jungle and the Pantanal, while the yellow rhombus would represent the country's gold reserves (Brazil had once the largest gold mines in world. From 1500 to 1900, more gold was extracted from the Brazilian territory than it existed in world before).
Actually, the current Brazilian Flag was inspired at the old Imperial Brazilian Flag. The two flags are almost identical, and the Green color represents the Bragança Royal Family of Pedro I, the first Emperor of Brazil; and the Yellow color representing the Castela e Lorena Royal Family of Leopoldina, Pedro's wife.
The difference between the old Imperial Flag and the current Republican flag is the Royal Coat of Arms, that was substituted by the blue circle, which is a portrait of the sky over Rio de Janeiro on the morning of November 15, 1889 -- the day of the Declaration of the Republic. It is represented as seen from outside of the celestial sphere (i.e. the view is mirrored). Each of the 27 stars represents a different state and the Federal District. The number of stars changed within the creation of new states. Originally, there were 21 stars.
The star that represents the Federal District is Octans, and its position near the south celestial pole makes it visible across almost the whole country, every day and every hour. Also, all the other stars represented at the flag circums Octans. These facts give to this star a special meaning representing the brazilian capital.
The motto "Ordem e Progresso" (Order and Progress) is inspired at Auguste Comte positivism motto: "L'Amour pour principe et l'Ordre pour base; le Progrès pour but" ("Love the Principle and Order the Basis; Progress the Aim").
The current national flag and ensign of Brazil was adopted on May 12, 1991.
The Stars
The constellation of southern cross is on meridian (indicated by the number 6 in the diagram). To the south of it, is the Polaris Australis (σ Octantis, numbered 7), representing the Federal District.
A list of constellations and stars on the map: