I was in a friend's backyard having a cigarette looking up at the sky, watching planes fly by. i saw what i thought was a very reflective helicopter and began watching it out of curiosity. it made no noise, and had a somewhat wobbly flight path at a fairly (but not completely) constant slow to medium speed, moving unlike what a helicopter is capable of. i saw it at a low angle coming from behind the house blocking the sky (perspective) looking north towards gowanus and park slope from my location in kensington. it began in the north sky and moved west, then northwest, away from me. i clearly observed a large metallic reflective silver disc with moving/pulsating golden lights. the most prominent light was circling the disc as it was moving from the top to the bottom and back again like a helix, making me think the object may be spherical, even though the structure was clearly a disc. this main light appeared to move from above the structure to below the structure, with an observable air gap between said light and structure when it reached its apex. other lights observed on the object seemed as if reflections of sunlight upon a moving sphere, moving flashes, which were golden yellow in color. by the time i was certain this was not a helicopter, plane, or other known aircraft, and overcame my sense of absolute wonder, i called out to the person nearest to me, but it was flying lower in the sky, and was blocked by a fence on the north side of the backyard which said person was leaning up against and they did not observe it. the sighting lasted approximately 15-30 seconds and i did not have time to take a photo or video with my phone. approximate flight path was heading north-northwest over west brooklyn, passing over prospect park, gowanus, park slope, and red hook.