This triangled-shaped aircraft was very large and made a very loud buzzing sound and it also had a green glow.I was in backyard it was about 8:00 at night when I heard a loud weird buzzing sound. When I spotted a triange shaped aircraft. It was just floating there I thin air, a green glow around its triangle body. But there was a distinct marking on a silver colored circular cone on the bottom of it. Suddenly rose up to about 400 feet and with immense speed it took off.