16 Psyche

16 Psyche ( SY-kee) is a large M-type asteroid, which was discovered by the Italian astronomer Annibale de Gasparis, on 17 March 1852 and named after the Greek goddess Psyche. The prefix "16" signifies that it was the sixteenth minor planet in order of discovery. It is the largest and most massive of the M-type asteroids, and one of the dozen most massive asteroids. This body has a mean diameter of approximately 222 kilometers (138 mi) and contains about one percent of the cumulative mass of the whole asteroid belt. It was thought to be the exposed core of a protoplanet, but observations reported in 2020 have cast doubt on that hypothesis. Psyche will be explored by NASA, with a spacecraft of the same name, marking the first time a human-made object will journey to a metallic asteroid. The spacecraft was launched on 13 October 2023, with an expected arrival in 2029.