Just a year prior, astronomers had discovered Eris, a frozen body whose orbit is farther out from Pluto's.
Then came the debate of how many more such bodies in the Kuiper Belt had to be declared planets.
The Union ultimately decided to fix a definition of a planet that eventually dislodged Pluto, Eris and many other similar bodies.
As the world observes the 20th year of this decision, another debate is simmering over whether to welcome back Pluto as a planet.
After cruising 4.8 billion km over nine-and-a-half years, the spacecraft flew within 12,500 km of Pluto.
Just a year prior, astronomers had discovered Eris, a frozen body whose orbit is farther out from Pluto's. It raised an astronomical question: should Eris be declared the 10th planet? Then came the debate of how many more such bodies in the Kuiper Belt had to be declared planets. The Union ultimately decided to fix a definition of a planet that eventually dislodged Pluto, Eris and many other similar bodies.
As the world observes the 20th year of this decision, another debate is simmering over whether to welcome back Pluto as a planet. This is because in 2015, the world discovered more about Pluto’s conditions which suggested that it could fulfil the third condition to be a planet.
US space agency nasa launched its New Horizons flyby probe to Pluto on January 19, 2006. After cruising 4.8 billion km over nine-and-a-half years, the spacecraft flew within 12,500 km of Pluto.
The images sent introduced us to a Pluto that had never been imagined. It has nitrogen ice glaciers visually similar to Earth’s ice sheets; big ice mountains measuring over 3,000 metres in height; an atmosphere filled with layers of nitrogen haze; and active geological activity like on Earth and Mars. And, Pluto has five moons.
Alan Stern, then principal investigator of the New Horizons Pluto mission, may have had a premonition of these discoveries on the day Resolution 6A was passed (much before the images were seen), given that he said, “Once Pluto gradually comes into focus and you see its complex surface, its system of moons, and its atmosphere, no one will be able to say, ‘That is not a planet’.” He added, “Pluto maintains a spherical shape through its own gravity and has five moons. Geo-physically, it is a fully fledged planet.”
