Pluto: No Longer a Planet Controversy

The question of whether Pluto has lost its planetary status has always been a hot topic of discussion between the scientific community and the public. In 2006, the International Astronomical Union (IAU) passed a controversial resolution to remove Pluto from the list of planets. This decision has sparked widespread controversy and discussion, with one side represented by Mike Brown, an astronomer at the California Institute of Technology, who is famous for discovering a new celestial body beyond Pluto, and the other side represented by Philip Metzger, a retired planetary physicist at the Kennedy Space Center of the National Aeronautics and Space Administration (NASA).

Brown believes that Pluto's dwarf planet status is a "silly term" that was secretly planted in the IAU vote by Pluto supporters in the hope of restoring Pluto's planetary status. He points out that taxonomy is part of science and that the public's astrology-based classification is of no use to science.

Metzger believes that the definition of a planet established by the IAU in 2006 is problematic, that they have no power to vote, and that they violated their own charter. He points out that the definition of a planet should be scientific, not based on some unknown metric. If Pluto were discovered today, no one would say it is a planet.

In discussing the criteria for planet status, Metzger mentioned three conditions set by the IAU: a planet must orbit directly around a star, be large enough to pull itself into a circle through its own gravity, and gravity dominates its orbit, clearing out the influence of other bodies on its orbit. However, they did not define what these conditions meant.

Brown believes that the invention of digital cameras has enabled astronomers to discover more large objects like Eris, which has forced them to abandon Pluto's planetary status. If Pluto were discovered today, no one would say it is a planet.

As for whether the solar system should have only eight planets, Brown said there is no magic number, but rather that astronomers are forced to acknowledge reality. If Pluto is redefined as a planet, the solar system will have 200 more planets, many of which will be beyond Neptune.

Metzger believes that we should teach the concept of planets as an evolving concept, rather than fixing on the number of nine planets. The solar system is a dynamic universe, and things are changing and evolving.

Regarding the search for the ninth planet, Brown said that the existence of the ninth planet is a hypothesis that can explain many unexplained phenomena we see there. However, until we point the telescope at it and see it, it is only the best hypothesis to explain these phenomena.
Finally, Metzger said that people's attachment to Pluto is due to the amazing photos taken by the New Horizons spacecraft when it flew past Pluto. Pluto is not only a planet, but also similar to Earth in geology, climate and material composition.

Overall, the question of whether Pluto has lost its planetary status has sparked widespread discussion among the scientific community and the public. Both those who support Pluto and those who oppose it have debated based on their own views and evidence. However, the controversy has not been resolved, but has instead stimulated more discussions about the definition of planets and the development of the solar system.

References:

Did Pluto ever actually stop being a planet? Experts debate. https://www.nationalgeographic.com/science/article/pluto-planet-dwarf-planetoid-solar-system