Six of Earth's neighboring planets — Mercury, Venus, Jupiter, Saturn, Uranus, and Neptune — will briefly appear in the sky on the same night, starting Sunday (Aug. 17). When you purchase through links ...

With Mercury joining the show, all seven of Earth’s celestial neighbors will be present at dusk this week. By Katrina Miller Astute skywatchers may have already seen the striking line of planets ...

This article was originally featured on The Conversation. Are planets in the solar system that are closer to the Sun older than the ones further away? – Gavriel, age 10, Paducah, Kentucky A cloud of ...

Planetary size was determined pre-spacecraft by measuring the planet's angular diameter and its distance from Earth (in AU, later converted to terrestrial units after the AU was accurately measured ...