Jakarta, CNBC Indonesia – For decades, schools taught there were 9 planets in the Solar System. However, Pluto’s status as the smallest planet has been lost since 2006.
In 2006, the International Astronomical Union (IAU) changed Pluto’s status from a planet to a dwarf planet.
This decision is because the astronomers who make up the IAU face a dilemma. The options are either to choose to label hundreds of objects they discover in the future as planets for Pluto status or to kick Pluto out of the ranks of planets in the Solar System.
They chose the second option. Hundreds of scientists voted to remove Pluto from the list of planets.
Then, why is Pluto not a planet anymore?
When the IAU officially defined the word “planet” for the first time, Pluto didn’t quite fit the bill.
Quoting pages PopsciThursday (26/1/2023) to be able to maintain its planetary status along with Earth, Saturn and others, it must go through three stages, namely the planet must orbit the sun, the planet must [mendekati] round shape, and its orbit must be clear of other objects.
Pluto does pass the first test, though, as it revolves around the sun every 248 Earth years. However, by other standards it falls short.
In the second test, Pluto could also pass. But explained, smaller asteroids [yang mengorbit matahari] can indeed have a strange shape. Itokawa, for example, looks like a lumpy potato.
But as the mass of a celestial body increases, its gravitational force pulls the expanding part toward the center, creating a spherical shape. Pluto is large enough to force its shape to be round.
Pluto’s main challenge is on the third standard, which is at the heart of what many astronomers think of when they hear the word “planet.”
The orbits of the other eight planets in the Solar System are clear of other objects. However, Pluto is different. If you look at the Solar System as a whole, it is located between the asteroids and planets.
As far as astronomers know, there are no nearby objects blocking Pluto. However, now researchers are starting to understand more about Pluto’s environment.
Rather than being the most distant planet, Pluto is the closest member of the Kuiper Belt, a donut-shaped ring of perhaps a trillion comets and icy spheres orbiting beyond Neptune.
At least 200 of these objects are large enough to be spherical, qualifying them as dwarf planets.
Like asteroids, they all move in the same way. Pluto, said astronomer from the California Institute of Technology, Mike Brown, is said to always be part of the asteroid herd.
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