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Navigational stars have a special role in the field of celestial navigation because they are among the most recognizable stars in the sky, both because they are bright and because they are part or lie in the vicinity of a prominent asterism. With an apparent magnitude of 1.91, it is only slightly fainter than Alkaid in the constellation Ursa Major, Sargas in Scorpius, Avior in Carina, and Menkalinan in Auriga, and it just outshines Alhena in Gemini, Peacock in Pavo, and Alsephina in Vela.Ītria is one of the 58 bright stars selected for navigation. Atria is by far the most distant and the most luminous of the three stars.Ītria is the 42nd brightest star in the sky. Unlike the triangle formed by the stars of the northern constellation Triangulum, which is elongated, the Southern Triangle is more equilateral in shape and its stars noticeably brighter. Informally known as Betria and Gatria, Beta and Gamma Trianguli Australis are both white (class F1V and A1V) main sequence stars and stand in contrast to the orange Atria. FactsĪtria forms a triangle with Beta Trianguli Australis and Gamma Trianguli Australis, which gives the constellation Triangulum Australe its name. However, the evidence for the presence of the dwarf companion is inconclusive. The object may be a class G0 dwarf with a mass similar to that of the Sun at a separation of about 50 astronomical units from the primary and a minimum orbital period of 130 years. A survey with the Wide Field Planetary Camera 2 (WFPC2) on board the Hubble Space Telescope (HST) discovered a faint object 0.4’’ south of the star. The star exhibits unusual characteristics for its class, including a strong X-ray emission and stellar flares, which could be explained by a magnetically active yellow dwarf companion with a hot corona. The AGB star would now be a white dwarf, but one has not yet been detected near Atria.Ītria (Alpha Trianguli Australis), image: WikiskyĪ study published in 2007 presented evidence that Atria may have a companion. Barium stars are explained by the presence of a binary companion – an initially more massive star (a carbon star on the asymptotic giant branch) that evolved first and contaminated the surface layers of the other star when the latter was still on the main sequence. Some sources give the spectral class K2III_Ba1 for Atria, which indicates a barium star. With a surface temperature of 4,150 K, Atria is 5,500 times more luminous than the Sun. If it were placed at the centre of our solar system, it would extend between the orbits of Mercury and Venus. The star has a mass of 7 solar masses and a radius 130 times that of the Sun. Star typeĪtria has the stellar classification K2 IIb-IIIa, indicating a giant (III) or bright giant (II) star appearing orange in colour. It lies at an approximate distance of 391 light years from Earth. With an apparent magnitude of 1.91, it is the brightest star in the constellation. Atria, Alpha Trianguli Australis (α TrA), is an orange giant or bright giant star located in the southern constellation Triangulum Australe.