JUST DISCOVERED       A 150-m wide asteroid, 2003 GG21, flew past Earth on April 3rd only three times farther away than the Moon. JPL's Near-Earth Asteroid Tracking program spotted it as it was receding from our planet on April 7th. This was Earth's closest encounter with a sizable asteroid this year. Even so, there was no danger of a collision. [ephemeris] [3D orbit]  Courtesy: NASA