Early observations of the planets revealed worlds far different from Earth, demonstrating that the universe was far more ...

It has now been 15 years since ex-planet Pluto was re-classified as a dwarf planet by the International Astronomical Union (IAU). On August 24, 2006, the IAU convened at its 26th general assembly ...

Astronomers had found Planet X, now called Pluto (after the Roman god of the underworld). However, after analyzing the new planet’s orbit, astronomers declared Pluto had too little mass to ...

That’s why the team put an upper bound on mass in their definition of a planet. And in case you’re wondering, Pluto weighs approximately 2.89*10 22 (1.31*10 22 kg).

Because then, as you decrease the mass of the sun, the mass ratio of Pluto, whatever you want, to the sun becomes a huge number. Then things, even not very massive things start acting like planets.

We’ve learned that the most common mass/size combination for a planet is intermediate between Venus/Earth and Uranus/Neptune: ... The 8 planets of the Solar System are all in; Pluto is clearly out.

Group of scientists published 5-year study arguing the current definition of planet was rushed, and should include Pluto, along with 100 other celestial bodies.