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Eris is slightly smaller but more massive than Pluto. The discovery of Eris lead to the reconsideration of the definition of a planet. There's a choice to be m
by exDM69 10y ago
Eris is slightly smaller but more massive than Pluto. The discovery of Eris lead to the reconsideration of the definition of a planet.
There's a choice to be made, either Pluto, Eris, Haumea, Makemake and Ceres are all planets or none of them are. And any new discoveries will be planets too. Or we come up with some kind of non-scientific arbitrary choice that Pluto is a planet because people on the internet got mad when it was changed to a dwarf planet.
Out of the dwarf planets, Ceres is my favorite because of the ingenious mathematics that lead to the determination of its orbit and thus verified that it's a planet. There was only a week's worth of observations before the planet went behind the sun and Carl Friedrich Gauss invented a method for initial orbit determination from three observations and pioneered the method of least squares to further refine the orbit to match the rest of the observations and the planet appeared where predicted a year later.
At the time of discovery in 1801, Ceres was considered to be the 8th planet (Neptune wouldn't be discovered for another 70 years). I don't know what eventually caused Ceres to be demoted from its planet status (perhaps because it's in the middle of the asteroid belt).
I think that dwarf planet is a suitable label to give Pluto. It's an insignificant blot of dirt in the outer solar system, and there are probably dozens like it waiting to be discovered.
- ianburrell 10y agoThe first four asteroids, Ceres, Pallas, Juno, and Vesta, were considered planets until the 1850s when lots more asteroids were discovered. https://en.wikipedia.org/wiki/Ceres_(dwarf_planet)#Classification https://en.wikipedia.org/wiki/Ceres_(dwarf_planet)#Classific...
- runarberg 10y ago> There's a choice to be made, either Pluto, Eris, Haumea, Makemake and Ceres are all planets or none of them are. This is half true. We don't strictly need a clear definition of a natural phenomena. Just look at the trouble we are having defining life. In fact, it might prove to be impossible to derive a solid definition. Yet most of us agree that all animals are living organisms, but fire isn't. In my view Pluto, Eris, Haumea, Makemake, etc. are all planets. Just because they fit my idea of what a planet is. I am less keen on grouping Ceres with them (but the reason is that I was raised knowing that it was an asteroid, so I am willing to reconsider). If voyager 1 stumbles upon an earth size spherical body in (say) 50 years, I will want to consider it a (rouge) planet, even though it is missing some criteria for the current definition. We can indeed call Pluto a planet and Ceres an asteroid. That is only consistent with how we treat most other categories of natural phenomena.
- derekp7 10y agoI like to think of the entire asteroid belt as a failed planet.