Boomerang, no lights, silent

Tonight at approximately 8:30 while looking up at the stars, I noticed a dark object moving through the sky. It was difficult to estimate distance and altitude. Though, I would say it was maybe at the altitude a helicopter flies. There were no lights or sound. It was moving at a speed consistent with a helicopter. My sighting lasted only about 10 seconds. My best estimate of the shape was something like a boomerang. It moved through the sky very smoothly unlike the flapping of a bird’s wings. Though I imagine if I misestimated the altitude, it’s feasible that it was a large bird gliding. After discussing it with a third party with pilot training, it was also mentioned that it may have been a B2 bomber.