Why Pluto Is Not A Planet ? Now We Have 8 Planetary Solar System.
As a kid we grew up being told that we have 9 planets and 1 star in our solar system. After 2006 this all has changed and we have 8 planets and 1 star in our solar system. Where did 1 planet go ? which is that missing planet ?
Answer to the question is Pluto ! After 2006, we do not count Pluto as planet and hence we have only 8 planets.
Why Pluto Is Not A Planet ?
Pluto was demoted from being planet at 26th general assembly of International Astronomical Union in Prague, 2006. Sealing Pluto is not a planet was a controversial decision as there were assembly members who wanted to keep it as planet only but sadly they could not hold up their argument well. They had no scientific justification for calling Pluto as a planet.
Pluto is a celestial body that is part of Kuiper belt . This belt is nothing but a lot bigger asteroid belt next to Neptune. There are about trillions of objects in Kuiper belt . Nearly all of them are chunks of ice and rocks just like Pluto. Since the Pluto was discovered well before all of this, we counted it as planet but as we studied Kuiper belt we found that there are many objects like Pluto and one of that is even bigger than Pluto. It’s name is Eris .
Eris is about 25% bigger by mass & twice as far from sun as Pluto. Scientists predict there may be up to 100s of things out there more or less the size of Pluto. So by logic, all of these objects should have been counted as planets or Pluto should not be counted as planet.
So in 2006, scientists decided a criteria.
To be a planet, an object has to have following
– Should orbit the sun.
– Should have enough gravity to pull itself into spherical shape (not exactly spherical but not elliptical also).
– Should have cleared pretty much everything out of its orbital path.
Pluto did satisfy first 2 criteria but failed in last one as it’s part of Kuiper belt there are many asteroids in it’s orbital path. Pluto is only 0.07 times the mass of everything else in its orbit. Where as earth is 1.7 million times the mass of everything else in its orbit.
Scientists came up with new category for celestial objects those satisfy first 2 criteria. The category is called Dwarf Planets . Hence from 2006, Pluto is not a planet but a dwarf planet !
To know more on Why Pluto Is Not A Planet ? watch the following video.
Courtesy : SciShow Space