According to the new definition of the name of a planet desired by the chief of the International Astronomical Union (UAI), There are 8 Planets in the world, downgrading Pluto to the rank of dwarf planet. This new definition removes Pluto from the planets of our system , relegated as a dwarf planet. However, the search for a 9th planet is launched …
Initially, this new definition was to extend the amount of planets within the system from 9 to 12 and lots of more within the following years. It should are ratified by the bulk of astronomers gathered in Prague during the 26th Congress of the International Astronomical Union.
A system with 8 planets
Planets in the world, they rejected this new definition, effectively disavowing their own executive committee. By refusing to expand the standards that outline a planet, astronomers are now satisfied with a system made from only eight so-called classic planets:
- The Earth, our planet.
According to UAI resolution B5, these eight planets meet the subsequent conditions:
they orbit round the Sun:
Planets in the world, have sufficient mass for its gravity to outweigh the cohesive forces of the solid body and maintain it in hydrostatic equilibrium, in an almost spherical shape;
eliminated anybody likely to maneuver during a close orbit.
Pluto: a dwarf planet among others
As for Pluto, it’s simply lost its status as a classic planet. When Pluto was discovered in 1930, it had been considered the ninth planet in our system, particularly due to its size, which was believed to be on the brink of that of Earth. But subsequent observations showed that Pluto, 5.9 billion km far away from the Sun, is really five times smaller (2,300 km in diameter) and 100 times lighter than Earth.
But, within the 1990s, thousands of objects like Pluto were discovered (including Sedna, Haumea, Eris, Makemake, Quaoar …) within the Kuiper belt, well beyond the orbit of Neptune. It therefore became difficult to feature thousands of planets to the classic ones already known to our system . this is often why the UAI decided to officially demote Pluto and therefore the other large objects within the Kuiper belt to a replacement class, that of dwarf planets.
Five objects are considered dwarf planets:
Officially, a dwarf planet may be a heavenly body that meets the subsequent 4 criteria:
It orbits around the Sun:
Planets in the world has sufficient mass for its gravity to outweigh the cohesive forces of the solid body and maintain it in hydrostatic equilibrium, in an almost spherical shape;
it didn’t eliminate other bodies from its near-space environment;
it is not a satellite from another planet.
The other planets: scattered objects
All other objects, which are therefore neither planets, nor dwarf planets, nor satellites of other objects and which have an elliptical orbit, are considered “small bodies of the Solar System” or scattered objects. At the beginning of October 2019, the list, maintained by the asteroid Center of the IAU, was quite 1,000.
For example, in November 2015, a replacement planet was discovered. Designated V774104, it’s 3 times farther away than Pluto and features a diameter of 500 to 1,000 kilometers. Its orbit remains undetermined: if it approaches our sun, it’ll be one among the dwarf planets whose orbits are often explained by gravitational interactions with Neptune.
Number of planets in our Solar System: a still heated debate
Since the invention in 1992 of the primary exoplanets, the classification of the planets has become far more complex and therefore the retrograde of Pluto has sparked heated debate.
Despite its downgrading, Pluto still arouses the interest of astronomers who would really like to understand more about this border guard of our system . The New Horizon spacecraft, the fastest spacecraft ever built (with almost 14 km / s), reached Pluto in July 2015.
What if the 9th planet was a primordial black hole?
Despite the emulation aroused by this search for the 9th planet which should be of a big size, it’s still not been discovered.
Therefore, astronomers hypothesize that it might be alittle region the dimensions of a ball .
“Our system may have a primordial region in orbit – a hyperdense mass of matter the dimensions of a ball . If so, we’d like to vary our approach in our research.” states MIT Technology Review.