Update
Only logged in members can reply and interact with the post.
Join SimilarWorlds for FREE »

Pluto will always be a planet in my book

Pluto's "demotion" was largely about politics.

Much of the following is based on the book "Chasing New Horizons", written by Alan Stern and David Grinspoon. Stern was in charge of the New Horizons mission to Pluto.

Pluto was discovered by an American "research assistant" at Lowell Observatory, named Clyde Tombaugh. (He eventually went on to get a degree in astronomy.) This was in 1930. (Tombaugh eventually wrote "Out of the Darkness", which describes how he made that discovery. I enjoyed reading it years ago, but it is a very nerdy book, and not for everyone.)

Many years later, a British astronomer named Brian Marsden developed a personal animosity toward Tombaugh, and in 1980 Marsden told Tombaugh that he intended to erase Tombaugh's legacy and see to it that Pluto got reclassified as an asteroid.

And so, on the very last day of the 2006 Conference of the International Astronomer's Union (IAU) Marsden and his team introduced a very restricted definition of a planet. It was voted on and approved by the small crowd on hangers-on in the final afternoon of the conference -- less than 4% of IAU membership participated in the vote. Pluto got renamed a "dwarf planet."

Meanwhile, there is another group of scientists called planetary scientists, who are a bit different from astronomers in their focus. Planetary scientists study the geology , meteorology, and potential biology of individual planets, as worlds. To them, Pluto was still a planet. The fact that Pluto did not have enough gravity to clear out all debris in its orbit (which was central to the IAU's new definition of a planet) struck them as irrelevant to what they studied. In fact, within two weeks of the IAU vote, planetary scientists sent a petition , with more signatures than the total number of people voting at the IAU conference, declaring that they did not recognize the authority of astronomers to define what a planet was, that the adopted definition was flawed, and that they would not use it.

In my own experiences with my little telescope, I learned early on that I am more interested in observing the moon and planets than I am in looking at stars and galaxies. That is, I have the temperament of a planetary scientist, rather than of an astronomer.

Pluto is still a planet to planetary scientists. And it is still a planet for me.
This page is a permanent link to the reply below and its nested replies. See all post replies »
ArishMell · 70-79, M
I did not know the history but never understood the purpose of the "demotion".

I thought the great and good of professional astronomy had created some rather subjective definition of a planet based on minimum diameter, but I don't know if they have.

The notion of basing a planet on its ability to keep its sphere of influence tidy seems a bit odd, given that Saturn still has a gigantic quantity of rubble orbiting it as its rings, and Jupiter an impressive collection of discrete satellites.
This comment is hidden. Show Comment
DrWatson · 70-79, M
@ArishMell In the definition they accepted, bodies orbiting the planet do not count as debris in the planet's orbit.