In 2005, Mike Brown discovered a tenth planet in the solar system, which was named Eris. Eris was about as big as Pluto (which was still a planet back then) and it orbited around the sun at a distance nearly three times greater.But the existence of Eris raised troubling questions, such as: What’s a planet, exactly? And if Eris is a planet, why not also various other small spheres that orbit the sun? This led to the categorization of Eris and subsequently Pluto as dwarf planets, a polite term for ‘you’re not a planet anymore.’ Thus the solar system was left with eight planets, instead of ten.
Recently, Brown and his colleague Konstantin Batygin have found evidence for an object that will qualify as being a full-fledged planet which lies way out at what’s usually considered the edge of the solar system. They have not observed it directly, but inferred its existence based on the odd orbital characteristics of six bodies in the scattered disk portion of the Kuiper belt, which may have been caught in its gravitational sway. They arrived at this conclusion after more than a year of calculating, watching and conducting computer simulations. According to them, this planet is ten times more massive than earth and doesn’t come closer than two hundred and fifty astronomical units; and one astronomical unit is the distance from earth to the sun or nearly ninety three million miles. Even Pluto is only forty astronomical units away! In fact, it would take this new planet between 10,000 and 20,000 years to make just one full orbit around the sun. It took New Horizons 9.5 years to reach Pluto. A similar space probe will take nearly 59.3 years to reach planet nine when it is at its closest to the sun and 356 years when it is at its farthest (which is 1200 AU).
A ninth planet had long been hypothesized originally going under the name Planet X. It was first talked about more than a century ago, and looking for that planet was what brought astronomers to find Pluto.What hidden secrets can this planet nine hold? It is only a matter of time till someone observes it directly but it surely is going to be icy cold out there!