Fast triangular object in Oakland at night at 06:3

I was star gazing trying find constalations at 5:00 P.M.. I went back at 5:57 P.M.. I went outside again at 6:00 P.M.. I turned the lights outside my house was going to go back because it was cold but instead I went to the darkest place outside my house. I saw a triangular object. The three sides were curved and on the bottom there were three circles. The three circles looked light brown and the rest of the triangle was black. It had no lights , was low , looked smaller than an air plane , and went fast.