An object eight times the mass of Jupiter may have swooped around the sun, coming superclose to Mars' present-day orbit before shoving four of the solar system's planets onto a different course.

Skywatchers: A six-planet alignment peaks this week as Mars, Jupiter, Uranus, Neptune, Venus, and Saturn come together for ...

which slowly accretes to form systems of planets. For the past decade, astronomers have relied on the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to study young stars and their ...