The stellar classification of this star has undergone some revision over time, with the star being classified anywhere from an F-type main sequence star to a giant star.[8] In 2006, the NStars program assigned it a class of F5 IV,[3] where the luminosity class of 'IV' indicates this is a subgiant star that is exhausting the supply of hydrogen at its core and is in the process of evolving into a giant star. It has around 175%[7] of the Sun's mass with an estimated age of 1.1 billion years.[5] The star is radiating about 18 times the luminosity of the Sun from its outer atmosphere at an effective temperature of 6,533 K.[6] It is this heat that gives it a yellow-white hue that is typical for an F-type star.[10]
Eta Scorpii is rotating rapidly, with a projected rotational velocity of 150 km s−1.[7] This is causing the star to spin on its axis with a period of less than a day.[11] It is an X-ray emitter with its stellar corona giving off an X-ray luminosity of 4.4×1028 ergs s−1.[12] In 1991 it was identified as a possible barium star, as it displays an enhanced abundance of the element barium in its spectrum.[13] Overall, the abundance of elements other than hydrogen and helium, what astronomers term the star's metallicity, is similar to the abundance in the Sun.[5]
^ abGray RO, Corbally CJ, Garrison RF, McFadden MT, Bubar EJ, McGahee CE, et al. (July 2006). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 pc-The Southern Sample". The Astronomical Journal. 132 (1): 161–170. arXiv:astro-ph/0603770. Bibcode:2006AJ....132..161G. doi:10.1086/504637. S2CID119476992.
^Evans DS (June 20–24, 1966). "The Revision of the General Catalogue of Radial Velocities". In Batten AH, Heard JF (eds.). Determination of Radial Velocities and their Applications. Proceedings from IAU Symposium. Vol. 30. University of Toronto: International Astronomical Union. p. 57. Bibcode:1967IAUS...30...57E.
^Pizzolato N, Maggio A, Sciortino S (September 2000). "Evolution of X-ray activity of 1-3 Msun late-type stars in early post-main-sequence phases". Astronomy and Astrophysics. 361: 614–628. Bibcode:2000A&A...361..614P.