If you can observe the same area of the night sky over many days, the positions of the stars compared to one another do not change noticeably. However, if a starlike object starts to change its position relative to the fixed stars as the days go by, it is likely to be a planet. Mercury and Venus are never visible at midnight because Earth is farther away from the Sun than these two planets are, while Mars, Jupiter, and Saturn can be visible at any time of night. Uranus and Neptune are not visible without the aid of a telescope or binoculars.