Juno, the third asteroid ever discovered, was first spotted by astronomers early in the 19th century. It orbits the Sun with thousands of other bits of space rock in the main asteroid belt between Mars and Jupiter. One of the largest asteroids, at a size of 150 miles across, Juno essentially is a leftover building block of the solar system. Astronomer Sallie Baliunas of the Harvard-Smithsonian Center for Astrophysics and colleagues photographed Juno when it was located relatively nearby in astronomical terms, about 10 percent further from the Earth than the Earth is from the Sun. Even at that distance, Juno appeared very tiny in the sky. Imaging Juno at the high resolution needed to resolve surface details thus presented a challenge. To solve the problem, the scientists used an adaptive optics system connected to the 100-inch Hooker telescope at Mount Wilson Observatory. Their surface maps showed that Juno, like other asteroids, is misshapen rather than round, and that it has “sharp” edges. Even better, as Juno tumbled through space during the night of observing, a “bite” came into view – an area that appeared dark as seen at near-infrared wavelengths.