Your position regarding how to measure a planet...?!?

Question

If you could participate in a hot debate over the need for a new definition of a planet...
What would be the main point you'd argue? Would you be for or against it?, why and why not?, and where is your stance in the controversy it's created surrounding Pluto? Was demoting Pluto...the right decision?, why or not?

(Not asking for an essay, this is part of a research project)

Answer 1

The main reason for 'demoting' Pluto is two-fold:

It is not what it 'promised' to be.

It is only one of a whole family of objects in the same area of the solar system.

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When Pluto was discovered, it was following an analysis of perturbations of the orbit of Neptune. Calculations showed (at the time) that there should be a massive planet (a light gas giant, perhaps). These attributes were assigned to Pluto immediately after its discovery.

However, as it was studied, it was found to be much smaller than first thought and definitely could not be responsible for whatever perturbations had been detected on Neptune's orbit.

Even after a few years, it was clear that Pluto was a tiny object. But, as long as it was alone in its corner, it was not harming anyone and we kept it as a planet (the only one discovered by an American). It was good politics.

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In the early 1800s, four planets had been discovered between Mars and Jupiter's orbits. For almost 50 years, they were the only ones there. Astronomers were OK with these 4 small planets, even though they were small and appeared crowded on their orbits (compared to the other 'major' planets).

Then in the 1850s, more and more were discovered. They were smaller and smaller. it quickly became clear that these 4 objects were simply the bigger members of a whole, large family of small objects sharing a section of the solar system.

The original four lost their planet status and a new class of objects was created (minor planets). They were also called 'asteroids' because when you looked at them through telescopes, they still looked like stars (aster) while 'real' planets showed a disk.

The same thing happened: Pluto, Eris and others are simply the first few objects of a whole family of planetoids that occupy another section of space (Trans-Neptunian Objects).

Some of them are big enough to form a new family of objects (dwarf planets).


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The word planet comes from the Greek: aster planetes (moving star -- or, more poetically: wandering star). Anything light in the sky that moved was a planet:

Sun, Moon, Mercury, Venus, Mars, Jupiter and Saturn.

When Galileo discovered the moons of Jupiter in 1610, they were called 'planets' in the original text (in Latin).

However, as the Kepler heliocentric system got accepted, the definition of a planet was changed so that only objects orbiting the Sun could be called planets, and the objects orbiting planets became 'satellites' (from a Roman word that applied to people who kept around important persons -- what we today would call groupies).

Answer 2

Defining "planet" is sort of like picking out where "gray" appears when going from black to white. We know that black is not gray and that white is not gray, just like we know that a meteoroid and a comet are not planets and a star is not a planet. The problem is just where do we draw the lines. Pluto, like Jupiter, is what we say it is. There is no sign on Pluto saying "Dirty orbit, too small, not a planet, call me a dwarf". By the old definition, Pluto was rendered a planet, because "it orbits the sun in a relatively circular orbit and isn't in the middle of the asteroid belt, and we were looking for a planet when we found it so it must be a planet". Before we found Neptune and Pluto, we had already found Ceres, Vesta, Pallas, and Juno, and called each a planet. By 1850 or so there were a dozen asteroids that were called planets, along with 8 "real" planets. So the asteroids were reclassified as "minors". Now Pluto has been reclassified.
What Pluto or any other body is called is not as important as what it is. Labels are merely for our convenience and don't add to or take from the object being labeled. It is what it is.

Answer 3

To borrow a quote, "length concerns", and ol' pluto grew to become into got here across "lacking". Orbit stability additionally counts, and too many eccentricities thereof won't get you into the club, previous boy.