SPACE — The Solar System has eight planets and five dwarf planets. What differentiates the two?
The word “planet” comes from an ancient Greek word meaning “wandering star.” This is because for thousands of years, humans have watched the planets change their positions in the night sky. That’s how the ancients discovered the five planets: Mercury, Venus, Mars, Jupiter and Saturn.
Astronomers using telescopes discovered Uranus in 1781 and Neptune in 1846, and Pluto in 1930. The nature of planets changing their positions is unlike stars, which appear still and motionless when seen with the naked eye.
As time and technology developed, scientists discovered more objects beyond Neptune, in a place called the Kuiper belt. The Kuiper Belt is a place in space that holds “remnants” of the solar system, especially small icy objects.
Scientists then discovered three small objects named Eris, Haumea, and Makemake which were discovered in the early to mid 2000s. These objects are large enough to be considered planets. These three objects are all about the same size as Pluto.
Astronomers then suspected that there may be more icy objects in the Kuiper belt. They began to wonder: how many planets can be identified in our solar system? Twenty? Thirty? One hundred?
Dwarf planet definition
In 2006, and after much debate, the International Astronomical Union (IAU) produced a new definition for a planet. It was in 2006 that the term dwarf planet was first used.
According to the IAU agreement, a planet must orbit the sun directly. Planets must also be large enough to have a round or spherical physical shape.
Additionally, the planet must “clean up its environment.” This means that, apart from the moons that usually follow it, the planet may not share its orbit with another object of comparable size.
Objects that meet only the first two criteria, but not the third are now called dwarf planets.
Pluto was demoted from a planet to a dwarf planet
In 2006 Pulo lost its status as a planet and is now classified as a dwarf planet. Pluto does not meet the third requirement because there are other icy bodies in the Kuiper belt that are in Pluto’s orbital path. That controversial decision is still debated by scientists to this day.
At the same time that Pluto was downgraded, there were other objects that received new status. Ceres, once considered an asteroid, is now classified as a dwarf planet. Ceres is in the main asteroid belt, orbiting between Mars and Jupiter.
If you add up Pluto, Ceres, Eris, Haumea, and Makemake, the number of dwarf planets in our solar system becomes five. However, it is possible that the list of dwarf planets will increase.
There are hundreds of candidates, almost all of them in the Kuiper belt, potentially meeting the criteria for dwarf planets.
2023-12-06 23:35:00
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