A New Proposal to Add Planets to the Solar System

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#1 21 February, 2017 - 19:59
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A New Proposal to Add Planets to the Solar System


There is a new proposal to change the definition of a planet so that there would be hundreds of planets in our solar system rather than just eight.

Here is the current definition from the IAU:

a planet is a celestial body which:

  1. is in orbit around the Sun,
  2. has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and
  3. has "cleared the neighborhood" around its orbit.

to this:

A planet is a sub-stellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape adequately described by a triaxial ellipsoid regardless of its orbital parameters.

That definition would make the Moon a planet. We would also have other new planets like Ceres, Enceladus, Titan, Charon, and Pluto. Brown dwarfs would be classified as planets.

I kind of like the idea, because then there would be incentive to memorize more planets and create more interest in them. :)

On the other hand, should a moon be considered a planet? What is the boundary between a satellite and a planet?

Memorization is discussed, though I think that memorization wouldn't be that difficult:

Finally … what do you propose the acronym should be for our new planetary family?

There shouldn’t be such an crayon, there are simply too many planets. Knowing the names of them is, well, so 20th century. We don’t memorize the names of all the mountains or rivers of Earth or all the stars. We only used to be able to do that for planets because our technology was do primitive and we didn’t know there were so many. In the 21st century one only needs to know the names of famous planets, just like kids only have to learn the names of the larges rivers and mountains. Beyond that all you need to know is that there are many more and you can look them up on the web or in books.

What do you think about the idea?

Side note: here is an interesting chart of the different kinds of solar system bodies:

Euler diagram of solar system bodies

22 February, 2017 - 05:07
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For this subject, I will put on three glasses to view the matter from a few different angles: The point of view of science, the point of view of psychology and the point of view of a mother. In general, my opinion is a face to my desk.

First of all, the most complex one: science.

When looking at the chart you provided, one might say that it indeed needs some cleaning up. In reality, it is much clearer than it might make you suspect, as it really clearly explained what a certain object is, which then tells you something about his aspects. Some 'Small Solar system Bodies' are trans-neptunian comets, falling in three or even four categories, that tells you something about it that one large category just can't cut. If I tell you I am a woman, I tell you my category, but that leaves half of humanity to fit the same description. If I tell you I am a white mother in her mid-20s, I give you more categories ot work with, and thus allow you to do more specified research and comparisons between categories. Of course, there are blurry lines there, like, when saying 'mother', does that only includes biological mothers or also foster mothers? But the chart of objects in our solar system isn't much different, the lines are not an immediate stop.

Looking more closely at the chart, that is what you see. Charon is a trans-neptunian natural satellite, meaning it is a natural satellite (pluto's moon) which has an orbit outside of neptune's orbit around the sun. Now, it also might be a dwarf planet, making pluto part of a binary dwarf planet system, science is not sure yet. That uncertaintly is not a reason to discard a system we have, it just means that our current knowledge of reality has gray areas laying inbetween the black and white of the charts.

Also, all these objects pictured in the chart already are a certain category: "bodies of the solar system", which you could give the fancy name of "heliospheric bodies" or so and be done with it, I heard that the name for this is actually "worlds", but I have yet to find a conclusive statement for this, so I will go with the fancy name! Say you call all of them Heliospheric Bodies, and you erase all other categories shown in the chart. A scientist researching objects formerly known as comets will have to specify his area to clarify that his findings only apply to certain objects, so another scientist looking at jupiter would not argue about the difference in findings. So he might call them bi-tailed heliospheric objects, and he explains the traits of these Heliospheric bodies. Other scientists also focus on the same part, some who maybe change the edges of this group of bodies a bit. Soon the group will be accaepted in the scientific community as a specified set of objects within the group of heliospheric objects. So in the end, nothing would change, and you'd only waste more time that we could spend on research.

I do also feel like the researcher behind this initiative knows very little about the history of the planetary categories. When I grew up, we had nine planets. Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. But this story goes further back. One of the earliest systems on planets had mercury, venus, mars, jupiter and saturn all listed as planets, but also the sun and the moon. Basically, if it was bright and moved across the sky periodically, it was a planet. This was all before the dutch invention of the telescope and all humanity had was an eyball with 1x zoom. The category of planets started to be more specified to objects around the sun as the use of telescopes became big in astronomy, and more planets got discovered. Like Uranus in 1781 and Neptune in 1846. Before Neptune was discovered, astronomers also found various objects flying between Mars and Jupiter, and soon the eleven planets of the solar system included the seven known by then, plus Ceres, Pallas, Vesta and Juno (don't quote me on that order, I don't know the order). They kept finding more and more of those objects which all looked similar, but didn't look much like planets, so they were called asteroids and were no longer planets. Currently, the list of asteroids above 100m in diameter has about 150 million entries... glad I didnt have to learn those as planets of the solar system. The list later got Pluto as well, in 1930, hence the list of nine planets we knew and loved. Years passed and more discoveries were made, like pluto being not as large as neptune as previously thought, but actually being smaller than quite a fair lot of moons found around the solar system. Pluto's mass is about five times lower than that of our moon, but it remained a planet. As with the four now-asteroids, science found more and more objects looking like pluto, so they made an agreement: as long as all of those objects remain smaller than pluto, we keep pluto as a planet, even though it is surrounded by objects of the same composition and roughly the same size. Which happened in 2005, at the identification of Eris, first spotted in 2003. That meant that not only where there objects similar to pluto, some were larger than pluto, and all where called Kuiper Belt Objects, after their region: the Kuiper belt.

Looking at what is out there, I see no objective reason to categorize objects in the manner proposed by Dr. Stern.

The secord opinion is psychological in nature

When I first read about this, the article to me showed that the motivation for this lies in the scientist's feeling of contempt towards Pluto's demotion to "dwarf planet". A few years ago, another article came out with the same reason: nostalgia. That article too said that Pluto should be called a planet again, because "Dwarf Hamsters are Hamsters as well". People looking for reasons to soothe their feeling of nostalgia.

I too still think of pluto being a planet, or at least a special dwarf planet. But I disagree with the argument to make it a planet officially, because that decision is based on a biased opinion origination from subjective thoughts of nostalgic events, not on a beneficial step or idea to improve the course of scientific knowledge and research, as could be seen in the change from hydrogen classification to the Hertzsprung-Russel Diagram when looking at stars, which was a giant leap forward for astronomy.

My opinion is that science has to work with objective systems that show and categorize things the way they are, and with the rise of technology, science can actually improve the objectivity. All reason to not degrade ourselves to the subjectivity our brains are primed to use.

He might have actual objective reasons, but I have yet to read about those.

The last opinion is that of a mother, who is looking at her daughter going to school.

I love hearing her come home and tell what they have done at school, and a couple months ago they had a guest teacher telling about the stars and planets. My daughter loved it, and she couldnt wait to run outside after the sun had set to see Venus with her own eyes. She even set her alarm at 6 in the morning to be able to see jupiter and mars. That kind of enthousiasm is what I love to see, that is what gets people interested in science. A few weeks ago, she demanded that we went to an observatory because she had questions, so we did and I think she traumatized the people there with the sheer number of questions she had to ask (she might have inherited a bit of autism from me *blush*), and seeing the proudness on her face from knowing all planets of our solar system just makes me happy.

back when I was in school, we got to taste many fields of science. We went outside at night to find bats in a nearby forest. We build out own electrical circuits. We visited historical sites where we could dig up our own miniature dinosaur bones and build our own dinosaur skeleton. We visited various temples to get a brief taste of various religions and cultures. That is what makes all of that interesting, and while it is a subjective reasoning, it is the reason that makes me hope that science doesn't just make things bigger and more complex, but also smaller and easier, for the kids who are eager to know more about it.

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