Delta Crucisorδ Crucis, also identified as Imai (/ˈiːmaɪ/), is a star in the southern constellationofCrux, and is the faintest of the four bright stars that form the prominent asterism known as the Southern Cross. This star has an apparent magnitude of 2.8, and its proper name was adopted by the International Astronomical Union on 10 August 2018.[13] Imai is a massive, hot and rapidly rotating star that is in the process of evolving into a giant, and is located at a distance of about 345 light-years (106 parsecs) from the Sun.
The International Astronomical Union Working Group on Star Names (WGSN)[14] approved the name Imai for this star on 10 August 2018 and it is in the list of IAU-approved star names.[13]Imai is the name selected for the star designated Delta Crucis by the Mursi people of modern-day Ethiopia. The star Imai has some significance as when it "ceases to appear in the evening sky at dusk (around the end of August), it is said that the Omo River rises high enough to flatten the imai grass that grows along its banks, and then subsides." The Mursi use a series of southern stars to mark their calendar to track seasonal flooding of the Omo River.[15]
It is sometimes called Pálida (Pale [one]) in Portuguese.[16]
Delta Crucis is a member of the Lower Centaurus Crux (LCC) component of the Scorpius–Centaurus association, which is an OB association of massive stars that share a common origin and motion through space.[7] This is the nearest OB association to the Sun, with the LCC component having an age in the range of 16–20 million years.[19]
InChinese, 十字架 (Shí Zì Jià), meaning Cross, refers to an asterism consisting of δ Crucis, γ Crucis, α Crucis and β Crucis.[20] Consequently, δ Crucis itself is known as 十字架四 (Shí Zì Jià sì, English: the Fourth Star of Cross).[21]
^Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: B/gcvs. Bibcode:2009yCat....102025S.
^ abHouk, Nancy; Cowley, A. P. (1978), Catalogue of two-dimensional spectral types for the HD stars: Declinations -90 to -53, vol. 1, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1975mcts.book.....H
^ abGutierrez-Moreno, Adelina; Moreno, Hugo (June 1968), "A photometric investigation of the Scorpio-Centaurus association", Astrophysical Journal Supplement, 15: 459, Bibcode:1968ApJS...15..459G, doi:10.1086/190168
^Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veroeffentlichungen des Astronomischen Rechen-Instituts Heidelberg, 35 (35), Astronomisches Rechen-Institut Heidelberg: 1, Bibcode:1999VeARI..35....1W
^ abcdede Geus, E. J.; de Zeeuw, P. T.; Lub, J. (June 1989), "Physical parameters of stars in the Scorpio-Centaurus OB association", Astronomy and Astrophysics, 216 (1–2): 44–61, Bibcode:1989A&A...216...44D
^Underhill, A. B.; et al. (November 1979), "Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars", Monthly Notices of the Royal Astronomical Society, 189 (3): 601–605, Bibcode:1979MNRAS.189..601U, doi:10.1093/mnras/189.3.601
^Sokolov, N. A. (May 1995), "The determination of T_eff_ of B, A and F main sequence stars from the continuum between 3200 A and 3600 A", Astronomy and Astrophysics Supplement, 110: 553, Bibcode:1995A&AS..110..553S
^ abBernacca, P. L.; Perinotto, M. (1970). "A catalogue of stellar rotational velocities". Contributi Osservatorio Astronomico di Padova in Asiago. 239 (1): 1. Bibcode:1970CoAsi.239....1B.
