Editing Triangulum Australe (section)

===Bright stars===
In defining the constellation, Lacaille gave twelve stars [[Bayer designation]]s of Alpha through to Lambda, with two close stars called Eta (one now known by its [[Star catalogue#HD/HDE|Henry Draper catalogue]] number), while Lambda was later dropped due to its dimness.{{sfn|Wagman|2003|pp=303–04}} The three brightest stars, Alpha, Beta and Gamma, make up the triangle. Readily identified by its orange hue,{{sfn|Moore|2005|p=116}} [[Alpha Trianguli Australis]] is a [[bright giant]] star of [[stellar classification|spectral type]] K2&nbsp;IIb-IIIa with an [[apparent magnitude]] of +1.91 that is the 42nd-brightest star in the night sky.{{sfn|Schaaf|2008|pp=263–65}} It lies {{Convert|424|ly|pc|abbr=off|lk=on}} away and has an [[absolute magnitude]] of −3.68 and is 5,500 times more luminous than the [[Sun]].{{sfn|Ayres|Brown|Harper|2007}} With a diameter 130 times that of the Sun, it would almost reach the orbit of Venus if placed at the centre of the Solar System. The proper name Atria is a contraction of its Bayer designation.{{sfn|Kaler, Atria}} [[Beta Trianguli Australis]] is a [[double star]], the primary being a  [[F-type main-sequence star]] with a stellar classification of F1V,{{sfn|Gray et al.|2006}} and an apparent magnitude of 2.85.{{sfn|Nicolet|1978}} Lying only {{Convert|40|ly|pc|abbr=off|lk=off}} away, it has an absolute magnitude of 2.38.{{sfn|Schaaf|2008|pp=263–65}} Its companion, almost 3 [[Minute and second of arc#Symbols and abbreviations|arcminutes]] away, is a 13th-magnitude star which may or may not be in orbit around Beta.{{sfn|Kaler, Beta TrA}} The remaining member of the triangle is [[Gamma Trianguli Australis]] with an apparent magnitude of 2.87.{{sfn|Wielen et al.|1999}} It is an [[A-type main sequence star]] of spectral class A1&nbsp;V, which lies {{Convert|180|ly|pc|abbr=off|lk=off}} away.{{sfn|Schaaf|2008|pp=263–65}}

Located outside the triangle near Beta, [[Delta Trianguli Australis]] is the fourth-brightest star at apparent magnitude +3.8.{{sfn|Moore|2005|p=116}} It is a yellow giant of spectral type G2Ib-II and lies {{Convert|606|ly|pc|abbr=off|lk=on}} away.{{sfn|SIMBAD Delta Trianguli Australis}} Lying halfway between Beta and Gamma, [[Epsilon Trianguli Australis]] is an optical double. The brighter star, Epsilon Trianguli Australis A, is an orange [[stellar classification|K-type]] sub-[[giant star|giant]] of spectral type K1.5III with an apparent magnitude of +4.11.{{sfn|SIMBAD Epsilon Trianguli Australis}} The optical companion, Epsilon Trianguli Australis B (or HD 138510), is a white main sequence star of spectral type A9IV/V which has an apparent magnitude of +9.32.{{sfn|SIMBAD HD 138510}} [[Zeta Trianguli Australis]] appears as a star of apparent magnitude +4.91 and spectral class F9V, but is actually a [[spectroscopic binary]] with a near companion, probably a [[red dwarf]]. The pair orbit each other once every 13 days.{{sfn|Skuljan|2004}} A young star, its proper motion indicates it is a member of the [[Ursa Major moving group]].{{sfn|Croswell|2005}} [[Iota Trianguli Australis]] shows itself to be a multiple star system composed of a yellow and a white star when seen though a 7.5&nbsp;cm telescope.{{sfn|Hartung|1984|p=214}} The brighter star has a spectral type of F4IV and is a spectroscopic binary whose components are two yellow-white stars which orbit each other every 39.88 days. The primary is a [[Gamma Doradus variable]], pulsating over a period of 1.45 days.{{sfn|De Cat et al.|2009}} The fainter star is not associated with the system, hence the system is an [[Double star|optical double]].{{sfn|Hartung|1984|p=214}} [[HD 147018]] is a Sun-like star of apparent magnitude 8.3 and spectral type G9V,{{sfn|SIMBAD LTT 6522}} which was found to have two exoplanets, [[HD 147018 b]] and [[HD 147018 c]], in 2009.{{sfn|Ségransan et al. |2010}}

Of apparent magnitude 5.11, the yellow bright giant [[Kappa Trianguli Australis]] of spectral type G5IIa lies around {{Convert|1207|ly|pc|abbr=off|lk=off}} distant from the Solar System.{{sfn|SIMBAD Kappa Trianguli Australis}} [[Eta Trianguli Australis]] (or Eta1 Trianguli Australis) is a [[Be star]] of spectral type B7IVe which is {{Convert|661|ly|pc|abbr=off|lk=off}} from Earth, with an apparent magnitude of 5.89.{{sfn|SIMBAD HR 6172}} Lacaille named a close-by star as Eta as well, which was inconsistently followed by [[Francis Baily]], who used the name for the brighter or both stars in two different publications. Despite their faintness, [[Benjamin Apthorp Gould|Benjamin Gould]] upheld their Bayer designation as they were closer than 25 degrees to the south celestial pole. The second Eta is now designated as HD 150550.{{sfn|Wagman|2003|pp=303–04}} It is a variable star of average magnitude 6.53 and spectral type A1III.{{sfn|SIMBAD HD 150550}}