GAMMA PAV (Gamma Pavonis). Way down to the south, not far from the South Celestial Pole, struts Pavo, the Peacock. Just 25 degrees off the pole is fourth magnitude (4.22) Gamma Pavonis. Instead of ranking third in brightness, as one might expect from its Greek letter, Gamma ties Lambda Pav for fifth place, and is well outranked by quite bright second magnitude Alpha Pav, which marks the northern fringe of the constellation eleven degrees northwest of Gamma. Not only is the star in the midlands of its rather large constellation, it falls well into the middle of the main sequence of hydrogen-fusing dwarfs, far from the spectacular fringe of stellar properties. As a mid-class F (F6) dwarf, it's much more in league with the class G2 Sun. Indeed the two are not all that different, the similarity sparking interest as we more or less look back at ourselves. The star is not very far away, just 30.2 light years (give or take a tenth). With a surface temperature of 6035 Kelvin, not all that much warmer than the 5780 Kelvin Sun, most of the light comes out in the visual spectrum, the star just 45 percent more luminous than the Sun. Luminosity and temperature then conspire to give a radius only 10 percent larger than solar. With a projected equatorial rotation speed of 3.7 kilometers per second, Gamma Pav makes a full turn in under 15 days, somewhat more than half the solar period (though one study suggests more). The theory of stellar structure and evolution then indicates a mass a bit higher than that of the Sun, perhaps five percent, and suggest that Gamma Pav might be somewhat more advanced in relative age. Alas, no planets have ever been found, nor has any debris disk that might mark their existence. With a Galactic speed relative to the Sun of around three times the usual value, and a metal content about 20 percent solar, Gamma Pavonis seems to be a member of the so-called old disk of the Galaxy, which houses stars a bit older than the dust-filled thin disk in which stars are currently being born, the low metal content perhaps explaining the lack of planetary companions. Nor for that matter are there any known stellar companions, the star perhaps just requiring a deeper look.

Written by Jim Kaler 11/01/13. Return to STARS.