GAMMA TRI (Gamma Trianguli). Its Greek letter name properly
fitting the third brightest star in Triangulum (the Triangle), fourth magnitude (4.01)
Gamma Trianguli anchors the eastern apex of one of the two
celestial Triangles (the other Triangulum Australe in the deep
southern hemisphere). Together with fainter Delta Trianguli and
Flamsteed's 7 Trianguli, this white class A (A1) hydrogen-fusing
dwarf at first appears as part of an attractive naked-eye triple
star (Delta and Gamma respectively Flamsteed 8 and 9). However,
the small gathering is simply a line of sight coincidence, as Gamma
is 118 light years away, while Delta (a fifth magnitude class G
double dwarf) lies much closer at only 35 light years, and 7 Tri (a
class A dwarf similar to Gamma) is much farther, 293 light years
away, quite dramatically showing the importance of factoring in the
third dimension. The star at first appears as just one more of its
class A kind, much like Sirius, though
farther away and one with no companion to keep it company. With an
estimated temperature of 9200 Kelvin, the star shines with the
luminosity of 28 Suns, its radius 2.1 times
solar. The temperature and luminosity coupled with the theory of
stellar evolution point to a 2.3 solar mass star with a fairly
youthful age of 200 million years. Not until we look at the
spectrum -- the rainbow of starlight spread from red to violet --
do we see that Gamma Trianguli is, for its class, a champion
spinner much in the mold of Altair,
though hotter. The spin washes out the "spectrum lines," the
narrow absorptions produced by the different kinds of atoms in the
stellar gases. Analysis of these features reveals that at the
equator, the star rotates with a speed of at least 208 kilometers
per second, 104 times that of the Sun. Since we do not know the
axial tilt, Gamma Tri might well be rotating even faster (if the
axis were pointing at us, for example, as nearly is Vega's, we
would note no rotation at all). Like Altair, the star is almost
certainly oblate instead of spherical. Factoring in the stellar
radius, Gamma Trianguli has a rotation period of only 12 hours, and
quite possibly less (as opposed to the solar period of 25 days).