My father and I were observing the ISS in our backyard when about a few minutes in I noticed an object similar to the ISS but much further up approaching from the south. I pointed it out to my father and we both agreed it was a stable white light like the ISS and nothing like an airplane or other flying vehicles in our area. Since we live in a heavy air traffic area we could easily distinguish the differences by comparing it to the planes in the sky at that time. The planes were giving off red, and white lights that would flash. This object was a steady white like the ISS but dimmer since it was higher up.It was going almost twice the speed of the ISS which compared to airplanes is already much quicker.The object disappeared in the north about 5 minutes after the ISS, which disappeared in the east.