Low level silent triangle shaped exhibiting seemingly impossible acceleration

My wife and I let the dogs out to relieve themselves. Usually we let them run around a bit while we stand on the front porch. My wife and the dogs went out just before me. The dogs were in the yard and my wife was just a few feet off the porch on the walkway. I was walking to the edge of the porch when something in the air and almost right above me caught my eye. The weather was clear with excellent visibility and a few scattered clouds. The moon and stars were bright. Both my wife and I were facing to the west. The entire sighting lasted for about 6-7 seconds, maximum.
I saw 3 lights in a triangle shape almost directly above me moving slowly to the west. At first, I thought it was an extremely low and slow commercial plane (I thought possibly in distress) with the anti-collision and landing light on. But anti-collision lights flash and these were not flashing. And the lights were large, circular, and glowing. It was also completely silent, not a sound. My eyes began to adjust to the dark and I could see that it was not an airplane at all. It was a triangular vehicle with 3 circular “lights,” one near the apex of each of the points of the triangle. It had a solid black body. I could see the stars disappear as the vehicle passed between me and the stars. I pointed at it and said to my wife “Look at that!” I could see in my peripheral vision that she looked up where I was pointing. At that exact moment the vehicle shot/streaked away to the west at about the same altitude, accelerating to what must have been multiple thousands of knots, instantaneously! There was no sound, not even that of air vortices that I would expect from a body moving through the air. We were both stunned.
I cannot make a real accurate estimate of the vehicle altitude because it was almost straight above me (until it shot away) and I don’t know how large it was. My estimate is that if it was a small fighter sized craft it would have been about 300-500 feet above ground level. If it was a 747 sized craft, I would estimate it was 1200-1500 feet AGL.