Scientists Propose Redefining Planets To Include Pluto And Over 100 Celestial Bodies


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Solar System with eight planets and one dwarf planet (Photo Credit:

In 2006, the International Astronomical Union (IAU), which promotes and safeguards the science of astronomy, passed a resolution that classified all bodies (except satellites) in our solar system into three distinct categories – planets, dwarf planets, and Small Solar System Bodies. To qualify as a planet, the body had to orbit around the sun, have sufficient mass for its self-gravity to pull it into a round shape, and have cleared the neighborhood around its orbit. Since Pluto did not meet the third criterion, it was downgraded to a dwarf planet.

Now, a group of NASA scientists not only want to restore Pluto’s original status but also reclassify over 100 celestial bodies, including our moon, as planets. The team, led by John Hopkins researcher Kirby Runyon, believes that a planet should be defined by the intrinsic qualities of the celestial body itself, not the external surroundings like its orbit or other objects. They argue that any object in our solar system that hasn’t undergone nuclear fusion and has enough gravitational pull to maintain a round shape, should be called a planet. Under this new definition everything, except for stars, black holes, asteroids, and meteorites, would be considered a planet. This means the number of planets in our solar system would expand from the current eight to almost 110! Among them would be Pluto, our moon, and all newly discovered worlds that are currently dubbed exoplanets.

Pluto (lower right) and, its moon, Charon (upper left) may soon be planets

Though that may sound a lot, especially for students who have to memorize their names, Runyon believes calling them planets will elevate the prestige of the celestial bodies and stimulate the public’s interest. This curiosity will lead to more exploration of our solar system. Additionally, given that most planetary scientists are closely affiliated with geology and other geosciences, the new definition is more relevant than the IAU’s astronomical definition.

While the idea seems valid, the researchers, who presented their arguments at the 48th Lunar and Planetary Science Conference held in Texas from March 20 to 24, still have to obtain approval from the IAU when it meets in Vienna in 2018. Until then, you will have to be satisfied with just eight planets!

Resources: Science Daily,,,

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  • OmalThursday, August 10, 2017 at 7:26 am
    I have to say that is cool
    • OmalThursday, August 10, 2017 at 7:23 am
      Very nice
      • turtlesturtles
        turtlesturtlesTuesday, June 13, 2017 at 6:27 am
        Pluto? Yes, I think should be a planet because it was once actually a planet. Our moon? No, who ever heard of a planet orbiting another planet? Our moon was never a planet, unlike Pluto, so in my opinion I think Pluto should, yes, be a planet as it once was, but as for the moon, no, it should stay a moon
        • cosmologist377
          cosmologist377Friday, December 1, 2017 at 1:59 am
          I think I disagree with that. You see, that depends. Pluto was declared as a planet as soon as it was discovered, but after 2006, the IAA announced it as a dwarf planet because it did not have a stable orbit as the current 8 planets. So, this is my opinion. ==> Like if you agree! :-)
        • CatbugMonday, June 5, 2017 at 8:59 am
          • peteral
            peteralFriday, June 2, 2017 at 2:58 pm
            Pluto deserves to be a planet. Even though it is not huge, it is big enough to have hydro-static equilibrium.
            • cosmologist377
              cosmologist377Friday, December 1, 2017 at 2:02 am
              Mister Peteral, I disagree with that. You see, hydrostatic equilibrium is a feature of the planet, and pluto was declared as a dwarf planet because it did not have a stable orbit, so do the other 4 dwarf planets. Size does not matter, then what do you say about Mercury? ==> Like if you agree! :-)
            • thWednesday, May 31, 2017 at 9:17 pm
              Wow I did saw a heart on pluto
              • LarryWednesday, May 24, 2017 at 10:03 am
                I still don't agree - moons are not planets - they orbit a planet - you may call them SUB-Planets or planetisimals - but based on mass they are not fully developed planets - IMHO
                • ribbitfrog
                  ribbitfrogFriday, May 19, 2017 at 7:20 am
                  I LOVE SCIENCE!!!!!!!
                  • batmanFriday, May 12, 2017 at 8:28 am
                    hi love it
                    • GO news Tuesday, May 9, 2017 at 4:29 pm
                      I can use this for anything! grade year person