Night sky or good binoculars, the planets appear as discs demonstrating finite size, and it is possible to observe orbiting moons which cast shadows onto the host planet's surface. Venus is the most prominent planet, often called the "morning star" or "evening star" because it is brighter than the stars and often the only "star" visible near sunrise or sunset, depending on its location in its orbit. Mercury, Mars, Jupiter and Saturn are also visible to the naked eye. Earth's Moon is a grey disc in the sky with cratering visible to the naked eye. It spans, depending on its exact location,
Star system star, or this closeness may be merely apparent, in which case it is an "optical" multiple star (meaning that the stars may appear to be close to each other when viewed from planet Earth, as they both seem to occupy the same point in the sky, but in reality, one star may be much further away from Earth than the other, which is not readily apparent unless one can view them from a different angle). Physical multiple stars are also commonly called "multiple stars" or "multiple star systems". Most multiple star systems are "triple stars". Systems with four or more