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

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 ...

Scientists believe that two asteroids might be fragments of long-lost "planetary embryos" from the early solar system.

NASA said the system is thought to be moving at least 1.2 million miler per hour, nearly twice as fast as our solar system.

Plate tectonics give Earth its mountains, earthquakes, continental drift and maybe even helped give rise to life itself. But do other planets in the solar system have them too?

The four planet-strong "planet parade" currently visible to the naked eye in the night sky for a short time after sunset will ...

The solar system is portrayed ... a reality show. If planets could talk, they’d be whispering about each other faster than Mercury on an espresso binge. Mercury on Earth "Thinks it’s the ...

While the composition of gas and dust in a molecular cloud is fairly uniform, everything changes once a star begins to form.

These embryos, somewhere between small planetesimals and fully formed planets, were abundant during the solar system's formative ... angrites that have fallen to Earth and compare them with ...

All of our solar system’s planets are lining ... in orbital periods between the planets. Mercury, which is closest to the sun, takes about 88 Earth days to complete an orbit, while Neptune ...