I saw a large white triangular craft in orbit moving north to south

When I spotted the craft it was almost directly overhead. It was traveling north to south at the same speed as a satellite travels across the sky. It was in the shape of an isosceles triangle but with the nose rounded. The craft was white but not a mirror like reflection of satellites. As it moved south it passed into the earths shadow and disappeared. There was no sound nor would you expect any at that altitude.