Astronomers Propose Changing the Definition of ‘Planet’ – Here’s Why

What is the true definition of a planet, and could there be a more accurate definition in the future? This is what we will find out in this article. Recent study Published in Planetary Science Journal She hopes to address this issue as a team of researchers from the United States and Canada. The possibility of arriving at a new definition of “planet” was investigated..

This study has the potential to challenge the old definition set by the International Astronomical Union (IAU), which established IAU Resolution B5 In 2006, this led to Pluto being demoted from a “planet” to a “dwarf planet”.

Here, Universe Today discusses this amazing research with the study’s lead author, Dr. Jean Luc MargotIn this interview, Dr. Margot, a professor in the Department of Earth, Planetary and Space Sciences at UCLA, talks about the motivation behind the study, the important findings, what steps need to be taken for the IAU to implement its new definition, and whether Dr. Margot thinks Pluto should be reclassified as a planet.

So, what is the motivation behind this study?

“The IAU B5 decision is problematic – it is vague and excludes exoplanets – and the problems will not go away on their own,” Dr. Margot tells Universe Today.

“Our society and the public deserve better definitions of important astrophysical terms like ‘planet’ and ‘satellite.’ We have had eighteen years to identify problems and think about possible ways forward. There is good reason to believe that in 2024 we are better prepared than in 2006 to deliver good results.”

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According to IAU Resolution B5, the current definition of a planet is:

(a) In orbit around the sun,

(b) has sufficient mass for its self-gravity to overcome the rigid body forces so that it assumes a hydrostatic equilibrium (approximately circular) shape, and

(c) He cleared the neighborhood around his orbit.

Unfortunately, this resulted in Pluto being demoted from a planet to a dwarf planet because it did not meet criteria (c).

In addition, the IAU resolution B5 is limited to planets within our solar system, specifically those orbiting a single star. In contrast, About 50 exoplanets Planets have been confirmed to orbit a single star within a binary (two-star) system. Therefore, the new definition by the International Astronomical Union that includes exoplanets may help create a better framework for planets throughout the universe.

While IAU Resolution B5 is a qualitative (non-mathematical) definition of planets, this latest study attempts to develop a more quantitative (mathematical) definition, or planetary classification, that could include planets and moons both inside and outside our solar system.

To this end, the researchers used a series of equations to calculate the “area clearing capacity of a planetary body,” which is consistent with Criterion (c) of IAU Resolution B5, to determine the approximate size a planetary body must be to “clear an area.”

Additional equations were also used to determine the difference between the planet and the moon as well. So, what are some of the most important findings from this study?

“We propose that planetary bodies can be classified on the basis of properties that can be easily measured: orbital elements and masses,” Dr. Margot tells Universe Today.

“We find that unsupervised clustering of solar system bodies according to orbital elements and masses leads to distinct groups. The clustering reveals that the satellites are different from the planets, and it also reveals that the eight planets are different from all other bodies. The existence of these groups and the gaps between these groups provide natural dividing lines for planetary classification.”

“We emphasize the focus on the ability to decontaminate an area in a specific time frame, as opposed to the case of decontaminating an area. The former is powerful and can be easily measured and monitored, while the latter is difficult to implement and difficult to quantify,” Dr. Margot continues.

“We propose a single timeline for purging all stars, stellar remnants, and brown dwarfs. We propose a definition that is consistent with the IAU recommendations, but we also consider potential difficulties associated with these recommendations. We propose a simpler mass-based proposal that avoids some of these difficulties.”

This proposal consists of the following definition:

A planet is a celestial body.

(a) orbiting one or more stars, brown dwarfs, or stellar remnants, and

(b) greater than 1023 kg, and

(c) Less massive than 13 Jupiter masses (2.5 × 1028 kg).

A satellite is a celestial body that orbits a planet.

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Headquartered in Paris, France, The International Astronomical Union was formed. On July 28, 1919, in Brussels, Belgium, with the aim of promoting and improving all aspects of astronomy, including scientific research, public communication, and universal education.

As of May 2024The IAU consists of 92 countries and 12,738 members. The IAU has held 32 General Assemblies during its history with the aim of establishing a scientific protocol or, in the case of planets, presenting a new definition at the 26th General Assembly in 2006.

Examples of more recent decisions include: Protecting radio astronomy from radio interference And Developments in Ultraviolet Astronomyboth at the 31st General Assembly in 2021. So, what steps need to be taken for the IAU to implement these three criteria for identifying planets?

“The IAU has an established process for considering and voting on proposed resolutions,” Dr. Margot tells Universe Today.

“In my opinion, the IAU should follow its established procedures and consider all reasonable applications. We failed in 2024, but we will likely resubmit the application before the 2027 General Assembly, and we hope to obtain a more positive outcome at that time.”

As mentioned earlier, the impetus for this study was the IAU’s B5 decision in 2006 which established a new definition of a planet, demoting Pluto from a planet to a dwarf planet based on the new criteria.

This was immediately met with skepticism from the scientific community, Including Dr. Alan Sternthe principal investigator for the New Horizons mission that visited Pluto in 2015, Pluto was demoted less than a year after New Horizons launched in early 2006.

This reply It has also been seen in politics. Several state governments, including California, New Mexico, and Illinois, have also publicly condemned Pluto’s demotion. So, in Dr. Margot’s opinion, should Pluto be reclassified as a planet?

“Pluto is an amazing planetary body that deserves to be explored,” Dr. Margot tells Universe Today.

“However, it does not make sense to classify Pluto among the eight planets. One may have legitimate concerns about the scope and accuracy of the 2006 IAU definition of a planet, but at least the outcome of the IAU decision was reasonable: Pluto does not belong to the eight planets and should have been classified in a different category. Our work is not focused on Pluto but on defining and generalizing the definition of a planet.”

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As of this writing, NASA has confirmed the existence of 5,690 exoplanets. This number continues to grow at a steady rate every day, which means that the number of exoplanets orbiting multiple stars will also grow.

Thus, the new definition of planet may provide a better framework for identifying and characterizing exoplanets and their exomoons (exomoons) as we continue to explore the universe.

This new study may help establish this framework by developing a quantitative approach to identifying planets and moons in and beyond our solar system, which could help shape our understanding of the universe and our place in it. Additionally, using mathematics to create a new definition may remove any subjectivity from the definition of planets as well.

“Nothing in our proposal is designed to keep the number of planets small,” Dr. Margot tells Universe Today.

“The cluster analysis pays no attention to human feelings. It could have resulted in a cluster of 8 planets, or 12 planets, or 50 planets, and we would have done exactly the same thing. He identified 8 planets.

“Readers who are saddened by the failure to recognize smaller bodies as planets should take comfort in the fact that these bodies are no less worthy of exploration. Taxonomic classification into one group or another is no indication of scientific importance.”

How will this new definition help scientists better understand planets and exoplanets in the years and decades to come? Only time will tell, and that’s why we care about science!

This article was originally published by The universe today. is reading Original Article.