GAMMA-2 NOR (Gamma-2 Normae). South of Scorpius and lost among brighter surrounding companions that include Lupus (the Wolf) and Ara (the Altar), obscure Norma (the Square, originally Norma et Regula, the carpenter's Level and Square) rates littl1e attention. The constellation's luminary, Gamma-2 Normae, is but fourth magnitude (4.02), and things go rapidly downhill from there. About all the small figure has going for it is a lovely place in the southern Milky Way. Roughly half a degree to the west of Gamma-2 lies fainter fifth magnitude (4.99) Gamma-1. The two have nothing to do with each other, Gamma-1 a rather unusual yellow-white class F (F9) supergiant 1440 light years away, Gamma-2 (the focus of our attention) a much more common yellow-orange class G (G8) giant only 128 light years distant. Gamma-2 Nor is understudied. From its apparent brightness, a temperature of 4735 Kelvin (needed to find the amount of invisible infrared radiation), and the distance, we calculate a modest (for a giant) luminosity of 45 times that of the Sun, a radius a only 10 times solar, and (adding the theory of stellar structure and evolution) a mass of between 2 and 2.5 solar. If the star is now quietly fusing core helium into carbon and oxygen, we get the lower mass, while if it is starting off its gianthood with a dead helium core and beginning to brighten, we get the higher. Ages then respectively come in at 1.4 billion and 600 million years. An upper limit of 12 kilometers per second to the equatorial rotation velocity yields a rotation period under 41 days, which is not much of a constraint. From the star's color there is some indication of dimming by the Milky Way's interstellar dust, which, if strictly corrected for, would raise the luminosity to 66 solar, the radius to 12 solar, and the mass as high as 3 solar, but the star is so close to us that actual dimming seems unlikely. A tenth magnitude star (about which nothing but apparent brightness is known), last noted (in 1959) as 45 seconds of arc away, is listed as a binary companion. But as with Gamma-1, there is no relation between the two. In 1834, the "pair" was separated by only 25 seconds of arc. The difference is far too great were the stars actually in orbit around each other, and the two are clearly just a line-of-sight coincidence, single Gamma-2 showing twice that apparently-paired proximity does not mean that the two are true orbiting mates.
Written by Jim Kaler. Return to STARS.