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.