Dwarf planets are planets too; they have structures, compositions, and processes very similar to the larger planets; they just happen to be smaller. Dr. Alan Stern coined the term "dwarf planet" in 1991 to designate a third class of planets in addition to terrestrials and jovians, small planets that are rounded by…

Sorry, I didn't see this message until today! I would love to discuss this stuff with you. You can reach me at laurel2000@gmail.com if you're still interested.

To many astronomers, Pluto IS still a planet, as are all dwarf planets. Hundreds of professional astronomers signed Dr. Alan Stern's formal petition rejecting the IAU decision. Stern is the person who first coined the term "dwarf planet," and his intention was to designate a third class of planets in addition to…

Some astronomers have proposed designating spherical moons as "secondary planets" or "satellite planets," given that these objects are complex worlds very much like the terrestrial planets, except for the fact that they orbit other planets instead of orbiting the Sun directly. The reference to these moons as…

Alan Stern recommends classifying moons large enough to be spherical as "satellite planets." This was actually proposed as far back as the 19th century, with the term then being "secondary planets." Either acknowledges that these larger worlds have the same characteristics as planets; they just happen to orbit other…

Thank you! I do consider Makemake and Ceres to be planets since both are clearly rounded by their own gravity and orbit a star.

Pluto IS a planet. Its status is a matter of ongoing debate. Only four percent of the IAU voted on the controversial demotion, and most are not planetary scientists. Their decision was opposed by hundreds of professional astronomers in a formal petition led by New Horizons Principal Investigator Dr. Alan Stern. …

I would rather save Vulcan for a hot exoplanet, but Pluto is not a "piddling TNO." It is a small planet.

Did you get to meet Patsy Tombaugh? She was at the launch.

A teacher can and should teach that the number of planets in our solar system is a matter of debate, depending on astronomers' understanding of the term "planet." It is also not a fixed number, given that new objects are constantly being discovered. I like Alan Boyle's description of four (terrestrials) plus four…

One should never "move on" from a bad definition that does more harm than good and causes more confusion than clarification. There is now a poor, badly written standard that a large number of astronomers do not like and will not use, one that completely ignores every solar system but ours. It does matter how we…

But objects in hydrostatic equilibrium are NOT asteroids or comets. Compositionally and structurally, they are very much the same as planets, with the only difference being they are smaller. All solar system planets have asteroids in their orbital paths. We cannot define objects solely by where they are; we also have…

Sure, why not? Teachers should teach the controversy and discuss both viewpoints. According to the geophysical planet definition, these objects are all planets too.

It matters for several reasons. First, many of the people who do care about this already have an interest in astronomy, so it makes sense they would see this as something to care about. More importantly, this issue points to much more serious questions, such as how do we know what we know? Who decides what is "truth?"…

If our solar system turns out to have 500 planets, then that is what it has. There is absolutely no scientific merit to the argument that "we cannot have too many planets because kids won't be able to memorize them." That is like saying we can't have billions of stars and billions of galaxies, or Jupiter can't have 67…

Yes, they do. Supporters of a geophysical planet definition, which does not require an object to "clear its orbit" to be a planet, recognize Ceres, Haumea, Makemake, and Eris as small planets. Vesta and Pallas are borderline objects, being nearly in hydrostatic equilibrium. The Dawn mission revealed Vesta to be far…

There is no Kuiper Belt Object larger than Pluto. Eris was initially thought to be larger than Pluto, but more accurate measurements in November 2010 showed it to be marginally smaller than Pluto though somewhat more massive. In any case, Eris is clearly spherical and therefore a planet as well. Pluto and Eris do not…

Your beliefs and hard work are not outdated. All of these professional astronomers share your view that Pluto is a planet: http://www.ipetitions.com/petition/plane…

A second pat on the back to his teacher from me!

Pluto is NOT an asteroid. An asteroid is a tiny rocky or icy body shaped only by its chemical bonds. Pluto is large enough to be rounded by its own gravity, a state known as hydrostatic equilibrium. It has geology and weather, and is differentiated into core, mantle, and crust just like Earth is. It may even have a…