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,
A Deepness in the Sky halo and is populated by incomprehensibly vast and powerful posthuman entities. "A Deepness in the Sky" takes place in the Slow Zone, though Vinge does not explain the connections, and the characters in the story remain unaware of the zones' existence. The sun's inexplicably strange behavior, the unusual planetary system (with only a solitary planet and several asteroid-sized diamonds), and the discovery of "cavorite" on the planet may indicate the system originated in the Transcend, though it is currently moving outward from the Unthinking Depths. Vinge's characters speculate that the Spiders descend from an ancient star-faring civilization, and that the