a little less than four times the distance of the outermost planet Neptune." However, the scientists' most surprising realization was that the flyby of an alien star billions of years ago could ...

As early as the 1840s, a tricky calculus foretold the existence of a planet beyond the orbit of Neptune. Calculations based on Neptune’s mass suggested that the ice giant’s orbit, and that of ...

An unidentified interstellar object, possibly eight times Jupiter’s mass, may have disrupted the solar system’s planets.

"BepiColombo's main mission phase may only start two years from now, but all six of its flybys of Mercury have given us invaluable new information about the little-explored planet." The ...

Also, Neptune's interior remains opaque ... activity and shot a series of dark plumes into space during Voyager's flyby, whose composition remains unknown. Visiting these faraway worlds requires ...