Our home galaxy boasts hundreds of billions of stars. Some of them emit lots of light, while others are dim. And tonight, the southern sky features a stunning contrast between two nearby stars: one powerful, the other feeble.
Both reside in the constellation Piscis Austrinus, the southern fish. If you look due south in early evening, you\’ll easily see the bright star, Fomalhaut. This white star is just 25 light-years from Earth.
Just south of Fomalhaut is another nearby star. In fact, Lacaille 9352 is even closer — a mere 11 light-years away. But you’ll never see it without some help, because the star emits only one percent as much visible light as the Sun does. So, close though it is, Lacaille 9352 is visible only through binoculars or a telescope.
Despite their vast difference in luminosity, both stars generate energy the same way: Nuclear reactions in their cores convert hydrogen into helium. But Fomalhaut was born with twice the mass of the Sun, so its center is hotter, making it burn brightly. In contrast, Lacaille 9352 was born with only half the mass of the Sun. So it’s faint, cool, and red — what astronomers call a red dwarf.
Red dwarfs may seem insignificant, but in one way they far surpass their brighter brethren: They account for about three-quarters of all the stars in the galaxy.
Script by Ken Croswell