Look up in nighttime sky anytime between now and July 16, and you just might spy our solar system's brightest asteroid. Vesta, a 326-mile-wide object residing in the asteroid belt between Jupiter and Mars, is about to make its closest approach to Earth in nearly two decades. But don't worry, unlike other close calls with asteroids in recent history, Vesta is in a stable orbit around the sun that will only bring it within 106 million miles of Earth. Nonetheless, this convergence will make it visible to the naked eye, with a magnitude brightness approaching a maximum of 5.3 this week. Unlike other asteroids, Vesta's internal geology mimics those of terrestrial planets, with a metallic iron-nickel core covered by a surface crust of basaltic rock. In fact, it's this "frozen lava" that gives Vesta its beautiful reflectivity, casting back 43 percent of all light that hits it. (For comparison, our moon only reflects about 12 percent of all light.) A 2011 visit by the NASA