Pluto, a planet or not? Controversies have forever surrounded Pluto. Many of us have grown up learning that there are 9 planets in the Solar System but not anymore. Pluto has yet again been demoted to a Dwarf Planet. Irrespective of its status as a planet, Pluto has its own tale to tell which has made its mark in the history of our Solar System. Tise story is brought to you by Obuli Chandran.

Narrator: Obuli Chandran


Hey everybody, this is Aasif, and welcome to Hello Educator!


Today’s episode is from Mango Science Radio and the science story is from Obuli Chandran. He will be sharing a story about Pluto which is a dwarf planet or a planet? It has always been confusing. So, I hope today’s episode is useful to you.

00:38  Hi, Mango Science Radio listeners. Hope you’re all doing good. Obuli Chandran here again. So, I’m going to share some interesting piece of history of our understanding of planet Pluto. It’s not going to be long but very interesting because Pluto has been a planet of fascination for me for a very long time, but I’m just calling it a planet because back then when I was studying in my school it was still called a planet.

01:06  Today it has been declassified or demoted from the status of being a planet to a dwarf planet, but it is currently being debated whether it should be put back into being called a planet. Back then when I was studying in my eighth grade or ninth grade in 2000- 2001, it was a planet. Of course, we didn’t have much information about it in the books, not because it was not found in my books, but people did not have much information about the planet, Pluto.

01:38  So, let me tell you a little bit of the history of finding little things about Pluto, from a historical perspective. It was in 1905, there was this astronomer Percival Lowell. He thought there might be another planet beyond the orbit of Neptune because he found some deviations in the orbits of Neptune and Uranus, very little deviations. He thought there might be a planet but again it was not found when he was alive. It was in 1930, there was another astronomer called Clyde Tombaugh. He was the first person to actually observe the planet Pluto through his telescope. It was very interesting back then. It had to wait for so long. It is the latest planet to be discovered on the time scale. For example, Uranus and Neptune were discovered much earlier, at least a couple of centuries before that or at least a century before that, and also they did not, even when it was observed through a telescope, it was not revealing much information because it’s too far away.

02:47  It’s really really far away that a telescope could just see it as a faint dot with the surface features not visible like. For example, if you observe Mars or Saturn using a bigger powerful telescope you could see at least something on it. Like, for example, you can see the red spot on Jupiter, you can see the clouds on Jupiter, you can see the polar ice caps on Mars. But Pluto was too far away that nothing was visible, so we did not know about Pluto for a very long time. It would need something as powerful as a Hubble Space Telescope to discover a little more about it.

03:26  So it was in 1994 when the Hubble Space Telescope, a telescope that is operating in space, was repaired and you know, it was put to work to observe Pluto. Then it discovered that there are more moons than we thought initially. But even it did not reveal much about the close-up features of what Pluto is made up of, what is the surface of Pluto like? It is very tempting to know. So I’m going to talk about a mission that was said to know about Pluto and the name of the mission is the New Horizons.

03:59  It was launched in the year 2006 in January. The launch was on January 19, 2006. So it started, and of course, it was one of the spacecraft that was launched with so much power that it reached the orbit of the moon in about nine hours after launch. This is one of the five objects that were set to leave the solar system; the other four spacecrafts that were leaving the solar system were Pioneer 10, Pioneer 11, Voyager 1 and Voyager 2. I think in one of my earlier stories, I talked about Voyager 1 and Voyager 2 having left the solar system already. So New Horizon was the fifth spacecraft that was set to leave the solar system.

04:44  So, back to knowing about Pluto. The same year it was launched, in 2006 in August, the planet Pluto was demoted to being called a dwarf planet after the spacecraft had been launched. Of course, it has nothing to do with that, it was launched and being demoted to a dwarf planet, but the International Astronomical Union (IAU), based on the revised definitions of calling something as a planet, put Pluto into the dwarf planet category and that was a very disappointing moment.

05:18  Though, when I was studying, I was in my first year of college when it happened. I did not know about the spacecraft being launched but I learned about Pluto being demoted to a dwarf planet and some news or something. I don’t remember it but I did not know about the launch until much later. Do you know how long it took for the spacecraft to actually go close to Pluto? It did not land on Pluto. It is something that we call a flyby of the planet. It goes as close to the planet as possible and then, you know, studies it, takes pictures and then analyzes it, then goes past it. It doesn’t get into an orbit around Pluto.

05:55  It was in 2015 that the spacecraft reached Pluto. So it was launched in 2006 and reached in 2015. That’s nine long years! So it has taken nine years for this New Horizon spacecraft to reach Pluto and guess what? The analysis of the pictures taken by the New Horizons spacecraft revealed a world that was spectacular and it revealed, for example, icy mountains, terrains. They even detected mountains as high as 3.5 kilometres, they found a lot of methane ice, they found one of its moons like Charon. They were able to take pictures of other moons like Nix, Hydra, Kerberos and Styx. They were able to take pictures of this particularly big moon Charon, and also they were able to actually measure the proper size of Pluto. It was about 1/5 of the diameter of Earth’s and it was even smaller than our moon, 2/3 of the Moon. Since it could not get into an orbit around Pluto, it was difficult to set it in an orbit into Pluto because the spacecraft was moving at tremendous speeds and it is really difficult to slow it down and get it captured by the orbit of Pluto. It had to flyby but nevertheless it is given us so much information about Pluto than we could ever get from anything else. And luckily, the trajectory of the New Horizon spacecraft was such that it was led to explore another object, something that we call as the Kuiper belt object – KBO region – where there are hundreds and thousands of comets, not hundreds and thousands probably billions of comets and icy objects, very similar to an asteroid belt that we have between Mars and Jupiter.

07:48  So there are these Kuiper Belt objects. It went past one of the other icy bodies called Ultima Thule. In 2019, it was also able to take a picture of that object. So now that it is done now it is on its way out of our solar system. So from not knowing anything about Pluto until 1905 and getting the smallest of hint that it might be there, to observing it actually for the first time in 1930, to actually taking a close-up picture in 2015, we’ve come a long way and science has helped us to understand very interesting things about things that we otherwise could not have known about. So that is my interesting piece of information for today. I’ll catch you again with another interesting story or a piece of information soon again. Bye. 

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