Decades ago, when observational techniques were not that technically advanced, scientists assumed and thus defined many objects in the Solar System according to their limited knowledge and expertise at that time. However, today’s advanced telescopes are questioning and demanding a newer look at all those researches and observations. With each passing decade, or let’s say now with the latest observational instruments and telescopes, the universe is opening up to unveil an amazing variety of objects that were never seen or thought of by humans before.

The most interesting part is the discovery of the distant worlds that reside in the Milky Way. And to make it further intriguing, the ones found might just be like our very own Earth. All this is because today scientists understand planets and stars better than they did previously.

But stars do not come in as many varieties as planets do; these small worlds are becoming more complex to understand with every new observation. In our own Solar System, we have a unique array of worlds orbiting our Sun; from very hot to the very cold gas giants, to the perfectly beautiful green and blue planet — Earth. However, there are many more worlds out there within our own Solar System that are being discovered and are still waiting to be discovered. Especially, the ones which are in a region outside the orbit of Pluto, in an area called the Kuiper Belt, outside the orbit of Neptune.

This is an icy region made up of thousands of small rocky worlds that are cold and distant. These rocky worlds are called KBO’s or Kuiper Belt Objects. We know very little about them but as they are in the outskirts of our Solar System, so very much in our own backyard. Scientists and researches are too eager to know what KBO are and what they are up to which ultimately brings us closer to defining what exactly a planet is!

It all started when astronomers all around the globe gathered for the planet debate regarding Pluto’s status as a planet. In other words, does this tiny world in the outskirts of the Solar System deserves to be called a planet where so many other bodies like this one also roam?

Some argued that since Pluto fits the planet definition of being round, orbiting its host star and having its own moons around it, it deserved the status. Some said that we do not know enough about the outer reaches of the Solar System to be sure, while others argued that since there might be other objects out there like this one, they could be called ‘dwarf planets’ or ‘plutoids’.

In 2005, Pluto’s neighbourhood revealed another icy object named Eris. According to the 2006 definition of a planet by astronomers: “a body that circles a sun without being some other object’s satellite, is large enough to be rounded by its own gravity, and has cleared it’s neighbourhood of most other orbiting bodies”.

It was the last part regarding ‘clearing the neighbourhood’ that almost made Pluto lose the battle because of the discovery of many such icy bodies in its region. So Pluto and Eris were called dwarf planets, which means that we were left with just eight major planets — Mercury, Venus, Earth, Mars, Jupiter, Uranus, Saturn and Neptune.

The term ‘dwarf planet’ also appealed to some researchers as they felt that such a small world, so far out, with an outlandish orbit, too elliptical, did not belong to the family of the other eight larger ones. Astronomers feel that the only reason Pluto was called a planet was because when it was discovered back in 1930, they knew very less regarding the region where it was detected.

But then researchers found another flaw with the above definition regarding the other eight planets as well. None of the other eight planets had completely ‘cleared its neighbourhood’, which brings us back to where we started. But then again if all these far away bodies are called planets, we would lose count by finding out more and more with each new discovery.

Nevertheless, scientists also think that there really is no reason to label these unique new worlds as planets as the term is difficult to define due to the variety of objects out there in the Universe. For instance, the latest telescopic observations have shown strange planets that do not have a host star at all which means that they do not circle a sun but just move around on their own in pairs, etc.

So what do we call them? In our own Solar System, if we just stick to the fact that all the worlds that are round due to the gravitational pull inside their core and are thus rounded and circle our Sun are called planets, then their count will soar to thousands. So what definition should we require?

According to a leading astronomer, Neil deGrasse Tyson, who is the director of The Hayden Planetarium in New York, should one categorise such worlds as terrestrial planets or rocky worlds like Earth, Mercury, Mars and gas giants such as Jupiter, Saturn, Neptune and Uranus and Kuiper Belt objects such as Pluto, Eris and the rest and others as asteroids.

Interestingly, Pluto’s moons, Charon and Ceres orbit on their own and their centre of gravity is not inside Pluto like Earth’s Moon which is controlled by the gravity inside Earth’s core.

As researcher Tyson puts it in his interview to www.space.com, “The word ‘planet’ has far outlived its usefulness. It doesn’t celebrate the scientific richness of the Solar System.”

The universe is vast, complex and has much still left to be discovered. We have not even touched the tip of the iceberg, so to say. So, do we really need fixed definitions for a diverse group of objects or should we just marvel at their uniqueness?

We can only wait and see what further observations will reveal about the magnificent cosmos.