Triangle (lat.Triangulum, Tri) Is the constellation of the northern hemisphere of the sky. Occupies an area of 131.8 in the sky. The stars of the Triangle are not bright: α is only the third magnitude.The Triangulum contains spiral galaxy M33 (the Triangulum galaxy), the third largest in the Local Group.Story. The Greeks often called him (Δελτωτόν) due to the similarity with the letter Δ; it was associated with the Nile delta and with Egypt in general, as well as with the triangular island of Sicily. Hipparchus and Ptolemy, who included this constellation in the „Almagest", already called it the Triangle (Trigonon, Τρίγωνον); Roman and medieval European astronomers used both types of names – Deltotum, Delta, Trigonum, Tricuspis, Triplicitas etc. Johann Bayer also used the name Orbis terrarum tripertitus („Three-part circle of the earth"), meaning the three parts of the world of ancient geography – Europe, Asia and Africa.In astronomy, these stars, together with γ Andromeda, formed the constellation Plow (APIN), described in the cuneiform document of the same name and referring to the „path of Enlil" – the band of northern stars. In the Chinese tradition, the stars β, γ and δ of the Triangle, together with part of Andromeda, belonged to the figure of the „heavenly commander and his subordinates."Jan Hevelius in his atlas „Uranographia", published in 1690, introduced alongside the traditional figure the Small Triangle (Triangulum minus), and called the first one the Great Triangle (Triangulum majus), but they were eventually merged again.Observation conditionsObserved throughout Russia, located between Perseus and Andromeda. The best time to watch is November. With the naked eye, in the constellation, you can see, depending on conditions and visual acuity, from 15 to 30 stars. In addition to galaxy M 33, the Triangle is known for many distant faint galaxies and a number of curious stars; there are no globular and open clusters, and there are no nebulae either. In addition, there are several known faint meteor showers with a radiant in the Triangle.Notable objectsThe Triangulum Galaxy, or M 33, is a spiral galaxy, the third largest member of the Local Group (after the Andromeda galaxy and the Milky Way). Its axis is turned to the line of sight at an angle of only 36 °, has pronounced spiral arms and a rather high integrated brightness of + 5.8m, however, due to its large angular size and, accordingly, low surface brightness, it turns out to be a difficult object to observe in the illuminated sky. A number of individual objects are observed in it, including bright spots of star clusters and the giant emission nebula NGC 604.NGC 672, NGC 784, NGC 925 and others are distant faint galaxies.3C 48 is a quasar discovered in the late 1950s and the first known object of this type.β Tri is the brightest (+ 3.0m) „star" in the constellation, a spectroscopic pair.α Tri, or Motallah, is the second brightest „star" (+ 3.42m), also a spectroscopic pair with an orbital period of only 1.7 days.ι Tri, or 6 Tri – a quadruple star system, consisting of two very close pairs that look like stars of spectral types G (+ 5.3m) and F (+ 6.7m), separated by about 4 arc seconds. When viewed through a telescope, they appear in contrast to yellow and blue, respectively, although the spectral type F corresponds rather to a yellow-white color.R Tri – a variable star of the Mira type with a brightness range from + 6.2m to + 11.7m and a period of 267 days.