Moon!!

The Moon is Earth's only permanent natural satellite. It is one of the largest natural satellites in the Solar System, and the largest among planetary satellites relative to the size of the planet that it orbits.

It is the second brightest object in the sky after the Sun. As the Moon orbits around the Earth once per month, the angle between the Earth, the Moon and the Sun changes; we see this as the cycle of the Moon's phases. The time between successive new moons is 29.5 days (709 hours), slightly different from the Moon's orbital period (measured against the stars) since the Earth moves a significant distance in its orbit around the Sun in that time.