Alpha Pyxidis is, at magnitude 3.68, the brightest star in the modern constellation Pyxis, the Compass. The star is occasionally called by the Arabic name Al Sumut, meaning "the way" or "the compass bearing".
Properties
The star is dim because it is 850 light years away. At that distance, being near the plane of the Milky Way, α Pyx is subject to 30% dimming by the pervasive dust of interstellar space. If the dust were not in the way, α Pyx would appear at magnitude 3.31.
Physically, α Pyx is a hot, blue-white class B1.5 III giant, with a surface temperature of 22,900 K. Corrected for dust absorption and ultraviolet light, the star has a luminosity nearly 18,000 times the Sun's, and a diameter 8 times solar. Its luminosity and temperature suggest that it contains 11 solar masses, and will soon begin to evolve off the main sequence, as its internal hydrogen is fused to helium. Born less than 18 million years ago, α Pyx seems to possess a circumstellar shell, and may be a multi-periodic β Cephei-type variables. Like many class B stars near the Sun, α Pyx has a low metal content; its iron abundance is about 60% solar.
[Adapted from STARS by Jim Kaler, Professor Emeritus of Astronomy, University of Illinois]