In a historic first, a spacecraft has reached a dwarf planet. NASA’s Dawn satellite entered orbit around Ceres, a mini-planet located between Mars and Jupiter, early Friday after a seven-and-a-half year journey. Ceres is the largest object in the asteroid belt, making up about one-third of the belt’s total mass. Little is known about the planet discovered 200 years ago, including if it has polar caps. The last remaining unexplored planet in the solar system is Pluto, which a NASA spacecraft will reach this July.