- ATRIA (Alpha Trianguli Australis). Among the easiest constellations to invent are simple triangles. There are two of them, one north (Triangulum) and one far south (Triangulum Australe). Of the two, the latter is the larger and brighter, its Alpha star (from which we get the modern proper name, “Atria”) a nice bright second magnitude (1.92), ranking 41st.