When I was in primary school, my teacher taught me that our solar system has the Sun at the centre and Nine Planets revolving around it in their respective orbits. By the time I was in middle school, the teacher had said Pluto was moving far away from the orbit, and it was clearly not visible. Now, the Scientists say that Pluto is a Dwarf Planet.

Illustration of Pluto


I was curious to know about the Curio Planet (Pluto). It is rightly remarked upon by the Dwarf due to its miniature visible size and distance from us. Pluto, which is at a distant region beyond Neptune, is known as the Kuiper Belt. It was discovered by an American Astronomer, Clyde William Tombaugh, in the constellation Gemini on February 18, 1930. 

On March 30, 1930, the New York Times announced, “In the little cluster of orbs which scampers across the sidereal abyss under the name of the solar system, there are, be it known, nine instead of a mere eight worlds.”

Inside the paper, another article suggested that the planet was “possibly larger than Jupiter and four billion miles away.” As we now know, Pluto’s distance from Earth ranges from 2.6 to 4.6 billion miles, and Jupiter is roughly 63 times as wide. Pluto is a complex and mysterious world with mountains, valleys, plains, craters, and maybe glaciers.

Pluto (minor-planet designation: 134340 Pluto)

Planet X renamed as Pluto

It was originally known only as Planet X, but The Times called it Pluto for the first time on May 25, 1930, when the Lowell Observatory in Flagstaff, Ariz., made the official announcement of the new name. 

The name Pluto is for the Roman god of the underworld, from a Greek epithet for Hades. Pluto’s planetary symbol was then created as a monogram of the letters “PL”. However, the most common astrological symbol for Pluto. Pluto has five known moons: Charon, Styx, Nix, Kerberos, and Hydra.

Pluto – Why dwarf?

A Dwarf Planet is a body other than a natural satellite (moon) that orbits the Sun, and that is, for practical purposes, smaller than the planet Mercury yet large enough for its own gravity to have a substantially rounded shape.

Planet Pluto was reclassified as a Dwarf Planet in 2006. In August 2006, the International Astronomical Union passed an official definition resolution for the term “planet”. According to this resolution, there are three conditions for an object in the Solar System to be considered a planet:

  • The object must be in orbit around the Sun.
  • The object must be massive enough to be rounded by its own gravity. More specifically, its own gravity should pull it into a shape defined by hydrostatic equilibrium.
  • It must have cleared the neighbourhood around its orbit. 

Pluto fails to meet the third condition. 


Pluto’s orbital period is about 248 years. Its orbital characteristics are substantially different from those of the planets, which follow nearly circular orbits around the Sun close to a flat reference plane called the ecliptic. Pluto’s rotation period, its day, is equal to 6.387 Earth days.

In traveling its eccentric path around the Sun, Pluto varies in distance from 29.7 astronomical units, at its closest point to the Sun (Perihelion – Nearness to Sun), to 49.5 AU, at its farthest point (Aphelion – Away from Sun).

The plains on Pluto’s surface are composed of more than 98 per cent nitrogen ice, with traces of methane and carbon monoxide. Pluto’s internal structure is Ice, Liquid Ocean, Silicate, and Core.

Pluto’s density is 1.860±0.013 g/cm3. Pluto’s diameter is 2376.6±3.2 km, and its mass is (1.303±0.003)×1022 kg. Its surface area is 1.774443×107 km2, or just slightly bigger than Russia or Antarctica. Its surface gravity is 0.063 g (compared to 1 g for Earth and 0.17 g for the Moon).


Extensive research continues in the attempts to classify Pluto in its rightful category. The uncertainty amongst different astronomers led to Pluto acquiring a dual definition. It possesses both characteristics of a planet and the Trans-Neptunian Objects (TNOs). Most astronomers still protest against these definitions since they still think that there is no solid proof that Pluto is not a planet. Thus, it takes more research to establish the fate of Pluto as a planet finally.

 For further exploration of educational content and insights, delve into the resources available on Chrysalis High.


Why was Pluto demoted from its status as a planet?

Explore the reasons behind Pluto’s reclassification, including the criteria for planetary status and how Pluto no longer met these criteria.

What are the arguments in favor of considering Pluto a planet?

Examine the perspectives advocating for Pluto’s planetary status, including historical context and the reasoning behind challenging its reclassification.

How has our understanding of Pluto evolved over time?

Trace the scientific discoveries and advancements that led to a reevaluation of Pluto’s classification, shedding light on the changing perceptions of this celestial body.

What impact does the debate over Pluto’s status have on astronomy?

Delve into the broader implications of the debate, including its influence on scientific classifications, public perception, and the evolving field of astronomy.