When we probe beyond our own galaxy, we see cataclysmic explosions that scatter the ingredients of new stars and planets into space. We trace the origins of galaxies by finding their ancestors, ragged masses of stars near the limits of the visible universe. And in an unexpected twist, we wonder why most of the universe consists of stuff we cannot see—including an utterly unknown form of energy that compels space to expand faster and faster as time goes on.
Just 15 years ago, these mysteries were beyond reach. We simply didn't have the right tools. Since then, astronomers have built major telescopes to gather the barest flickers of starlight, designed powerful electronic detectors to analyze the light, and launched satellites tuned to scour the sky in x-rays, infrared light, and other radiation. Together, this equipment has parted the curtains that shrouded much of our galaxy and the distant universe from view. It's a time of genuine revelation, a time when technology has extended our reach into the deep.
Some of this research has irresistible "gee whiz" appeal. One of my favorite advances teamed a laser beam and a high-tech mirror to help expose the wild physics near the monster black hole at the center of the Milky Way. Stars trapped in orbit around the black hole dive close to the center and then race back out again, like comets dashing around our sun. But to gain a clear view of stars so far away at the galaxy's core, astronomers must erase the blurring effects of Earth's atmosphere. They aim a laser high in the sky, its point of light jitter�ing from distortion caused by air currents overhead. A special flexible mirror at the base of their telescope counteracts the light's motion, allowing the telescope's instruments to record a sharp image. Such engineering wizardry is not your grandparents' astronomy.
The shapes and speeds of the stars' orbits show that the black hole tips the scales at four million times the mass of our sun. A few years ago, one of the stars passed so close to the center (but not close enough to plunge into the maw) that the black hole's gravity boosted the star's speed from 170 miles a second at the far point of its orbit to 5,200 miles a second—a remarkable 3 percent the speed of light. Other stars skirt past the black hole so perilously that gravity slings them around and expels them from the galaxy, a cosmic version of crack-the-whip.
We've also found that the cosmos is a pyromaniac's delight: Something's always blowing up. The main attractions are gamma-ray bursts, fierce explosions that momentarily outshine the stars in a billion galaxies combined. NASA's Swift satellite finds the bursts and sends their locations to telescopes around the world within seconds. Astronomers think most gamma-ray bursts herald the deaths of massive stars in a particularly violent breed of supernova—one that creates a black hole at its core.