Whenever planets are visible in the night sky, they always appear roughly along the same line. This path, known as the ecliptic, is the same one that the sun travels along during the day.
This happens because the planets orbit around the sun in the same plane. Dr. van Belle (director of science at Lowell Observatory in Arizona) likened the configuration to a vinyl record: The sun is in the center, and the grooves are the orbits of the planets around it.
Our point of view from Earth, then, is along one of those grooves, “looking out along the platter,” he said. This week, the planets are configured in such a way that all of them will be present in the sky at dusk from mostly anywhere on Earth.
-Katrina Muller writing for the New York Times
