I'm a space nut. The classroom I teach in is decorated with numerous posters of the planets, models of spacecraft, an awesome inflatable star globe. There's also a star chart, and surrounding the star chart are cutouts from the middle Brazilian flag.
Before I moved to Brazil, I just assumed that the stars were most likely in some order, but I barely paid attention to the flag so I couldn't remember how the stars were arranged within the flag itself.
When I arrived in Brazil, I was told that each star represented an individual state, and that apparently these stars were visible the night that Brazil became an independent country. Some time trawling through Wikipedia confirms that this is the case, and that these were the stars visible from "Rio de Janeiro at 8:30 in the morning on 15 November 1889, the moment at which the constellation of the Southern Cross was on the meridian of Rio de Janeiro and the longer arm [of the cross] was vertical."
The cool thing for me is that as I learn more and more about the astronomy of the Southern Hemisphere, the more Iearn about the Brazillian flag. For example the three southern most states Rio Grande do Sul, Santa Catarina and Paraná are represented by 'The Southern Triangle' (Triangulum Australe) constellation (which, sidenote is quite possiblely the most boring constellation ever imagined)
I also learnt how to find my way in the Southern Hemisphere. As a life long Northern Hemisphereian, I know that the pan of the Big Dipper points to the North Star, Polaris. It's easy to identify and once you spot it, you know where north is.
This method for orientating yourself doesn't work in the Southern Hemisphere, as these stars are never visiible south of the equator. However, there is a constellation, The Southern Cross (Crux) that points directly to the Southern Pole Star.
This is shown on the flag of Brazil. There is also deeper meaning to the use of the Southern Pole Star. The Federal District, Brasilia is represented by the Southern Pole Star. In the night sky, because of the Earth's rotation all stars appear to move around a fixed point.
This symbolism was used on purpose in the flag of Brazil, it represents that all of the States revolve around the capital.
I love this flag, I love flags and I love astronomy, so that's not really much of a surprise. The main reason I love it is because it's a lot like the country itself. It's complicated, with a lot of deeper meanings. It can appear messy when you first look at it, but as you learn more and more about it, you start to appreciate it and love it.