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xkcd #3063: Planet Definitions (xkcd.com)

submitted 4 days ago by [email protected] to c/xkcd

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Under the 'has cleared its orbital neighborhood' and 'fuses hydrogen into helium' definitions, thanks to human activities Earth technically no longer qualifies as a planet but DOES count as a star.

https://explainxkcd.com/3063/

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[–] CosmicCleric -1 points 4 days ago* (last edited 4 days ago) (1 children)

For some reason this subject always hits a nerve

Always bothers the hell out of me because of the politics that went into defining an arbitrary rule that makes no sense for identifying something that the rest of humanity has to obey, as well as that planetary scientists did not make the decision astronomers did, as well as that just a small subset of the international governing body voted the rule in, and not most/all of them.

Scientists should know better. They should not 'just call it a day' then make money by arrogantly selling books on the subject.

It's bad Science.

They should have used the term “dynamical dominance”, implying whether or not a body is the primary object left in its orbital area after formation. And this has its own issues, as solar systems change over time.

What does the environment around a body have anything to do with classifying the body itself? How would the body magically change if the area around it became crowded? It's a nonsensical criteria.

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[–] [email protected] 2 points 4 days ago (1 children)

That's a good question. Is being hydrostatic equilibrium the only physical attribute we should use for classification? Should Ceres be a planet?

[–] CosmicCleric 0 points 4 days ago (1 children)

Should Ceres be a planet?

I honestly don't know. I tend to say no, as it seems to just be a lifeless rock with no geological activity. I'd love to have rules to identify that, made by planetary geologists.

But I wouldn't want to disqualify a body with planetary characteristics like geological activity just because the space around it is busy, or it's orbit is not in the ecliptic plain, etc.

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[–] [email protected] 1 points 4 days ago (1 children)

Ceres does appear to be active in some form with cryovolcanoes, based on the 2015 Dawn mission.

I think focus ought to be more on what the qualifications are for the minor label. What does it mean to be minor?

[–] CosmicCleric 0 points 4 days ago

Ceres does appear to be active in some form with cryovolcanoes, based on the 2015 Dawn mission.

Then It's say that it was a planet, though IANAPG.

I think focus ought to be more on what the qualifications are for the minor label. What does it mean to be minor?

There shouldn't be a 'minor' nomenclature, it's a contrivance. It's a planet, or not

Also, to reiterate, the issue being discussed is one of disqualification, and not what qualifies. Identifying a body as a planet or not should not be done based on the criteria of the crowded or not nature of the space around it.

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