Does our Solar System have 9 planets or only 8? Astronomers have gone back and forth on that a lot, with Pluto now being classified as a dwarf planet. However, out beyond Neptune there could be ...

While most models of solar system formation predict perfectly circular and coplanar orbits for the planets, reality presents a slightly different picture. Successful Simulations: Approximately 1% ...

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.

All of our solar system ... so when the planets appear in the sky, they all appear roughly along the ecliptic. It isn’t a perfect line of planets, because their orbits are tilted slightly ...

those that are beyond the eighth planet, with highly “tilted” orbits compared to the ecliptic plane. This seemed odd and illogical as when the Solar system formed, it would be expected that ...

A newly discovered planet could change the search for life. Scientists have confirmed a super-Earth orbiting a nearby sun-like star. The planet, HD 20794 d, sits in the habitable zone. It could ...

The four-planet lineup that began in January concludes by mid- to late February, as Saturn sinks increasingly lower in the ...

A new study suggests that a planet-sized object may have passed through the solar system billions of years ago. Its journey could have permanently altered the orbits of the outer planets.

Here’s how it works. A planet-size object that possibly once visited the solar system may have permanently changed our cosmic neighborhood by warping the orbits of the four outer planets ...

This may explain the strange properties of the orbits of our solar system's planets, which are not quite perfectly circular, and all lie on slightly different planes. NASA artist’s conception of ...

Credit: MARK GARLICK/SCIENCE PHOTO A super-Earth planet that dips in and out of ... In the context of our solar system, Mars — on the outer edge of our habitable zone — orbits our sun at an average ...