PRAECIPUA (46 Leonis Minoris). While Leo is easy to admire, its modern-constellation counterpart, faint Leo Minor, which rides the back of the Zodiac's King of the Beasts, is not. Leo Minor, the "Lesser Lion," is so dim that few bother with him, and is so unimportant a constellation that no one would think of making Leo into "Leo Major," thus raising Leo Minor's rank. Because the modern constellations were invented long after proper names were assigned, most well after Bayer assigned Greek letters (and to some degree were carved from other constellations), the names of their stars can be a bit of a mess. Only one star in Leo Minor carries a Greek letter name, and that is "Beta;" there is no Alpha, and Beta Leonis Minoris is not even brightest, coming in second. The little constellation does have its charm however, mostly in a flat quadrilateral with the constellation's luminary, bright fourth magnitude (3.83) 46 Leonis at the eastern end (the "46" a Flamsteed number, the only Flamsteed number whose star ranks "number 1" in a constellation). Leo Minor is also one of the few modern constellation whose brightest star carries a proper name, 46 Leo Minoris also called "Praecipua," or "Chief," a "modern" term from Latin telling that "46" is the brightest star. Praecipua is otherwise ordinary, an orange class K (K0) giant-subgiant with a temperature of 4690 Kelvin. At a distance of 98 light years, it is not quite up to average giant brightness, radiating 32 solar luminosities into space, from which we derive a modest diameter (for a giant) 8.5 times that of the Sun. A star of around 1.5 solar masses, once a hydrogen-fusing cool class A star, it is now evolved, and is quietly fusing helium to carbon in its core. The star is known to be somewhat metal poor compared with the Sun, its iron content down by about a third. Of most interest perhaps is how well we know it. Recent accurate measures of angular diameter by the Navy Interferometer show it to be 0.00254 seconds of arc across (the separation of car headlights seen from a distance of 80,000 kilometers, 20 percent of the way to the Moon), which gives it a physical diameter 8.2 times that of the Sun, the agreement with the previously calculated diameter showing that we know the size, temperature, luminosity, and distance very well.
Written by Jim Kaler. Return to STARS.