The number of planets that orbit the sun depends on what you mean by “planet,” and that’s not so easy to define ...

Stargazers will be treated to a rare seven-planet alignment in February. This is what scientists hope to learn.

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.

NASA artist’s conception of a brown dwarf (main) and stock image of the planets in the solar system (inset). An object between 2 and 50 times the mass of Jupiter may have flown through our ...

"With an orbital period of 570 days, it is a relatively cold gas giant planet," said Guðmundur Stefánsson of the University ...

Our solar system contains planets, dwarf planets, asteroids and comets — but only one ... Some time in the last 65 million years, a little of its debris drifted back together into a floating rubble ...

The dwarf planet ... reached the inner Solar System only later. For the current study, the researchers looked for previously unknown deposits of organic material on dwarf planet Ceres.

The seven planets will not be perfectly aligned, but will appear in an arc across the sky due to their orbital plane in the Solar System.

Timing: Dusk after sunset, but before 9 p.m. local time There are eight planets in our solar system and one dwarf planet (Pluto ... will be the best nights to see all six planets closer together ...

Timing: Dusk after sunset, but before 9 p.m. local time There are eight planets in our solar system and one dwarf planet (Pluto ... planets that appear close together). A six-planet alignment ...