The year 2006 was a particularly eventful year in the astronomical and planetary science community as Pluto was relegated to the “non-planet” status thus bringing the total count of the number of planets in our solar system to 8.
The subject of what can be defined as a planet and the subsequent decision to demote Pluto as a non-planet by the IAU (International Astronomical Union) was a topic of debate and much deliberation in the scientific community.
Now, in a recent bid to revisit this decision and reaffirming the belief that Pluto, a group of astronomers from the John Hopkins University made a presentation at a scientific conference in Texas that aimed at restoring the lost status. This attempt at reinstating the planetary status would not only include Pluto but also include a 100+ celestial entities in the solar system satisfy the criteria to be called as a planet.
As per the definition laid down by the IAU previously, Pluto lost its planetary status owing to the fact that it was an extremely small sized object in the Kuiper belt that lies beyond the planet, Neptune. Due to the presence of several other similar bodies in the Kuiper belt as well as because of its orbital characteristics, Pluto was redefined as a dwarf planet. After having been discovered by Clyde Tombaugh in the year 1930, this was one of the biggest changes done to the manner in which the body was recognised by the scientific community.
Kirby Runyon, a scientist from the team, remarks that as per the definition put forward by the IAU for defining a body as planet,
1. It must not have undergone nuclear fusion at any point after its formation
2. Should have enough gravity to maintain a somewhat spherical shape and
3. It must also have a fixed orbit around the sun which has been cleared of other smaller bodies.
It is the third criteria that made Pluto unfit to be termed as a planet. Runyon argues that, since Pluto and the other 110 identified celestial bodies in the solar system fit the bill as far as the gravity, mass and orbital constraints are met in addition to having other secondary bodies such as satellites around them, they should be given the planetary status.
Planet or not, Pluto is one of the farthest entities of this solar system and is known to have a frigid solid surface. Other bodies such as satellite of Jupiter, Europa would also come under the ambit of this definition.