Why is pluto not a plant anymore?

Answer 1

The International Astronomical Union decided that Pluto was no longer a planet. The reason is that while Pluto is round, orbits the sun, and has three moons, it has not cleared (via gravity) its own orbit of debris. Instead, they decided to classify it as a "dwarf planet".

See the details below.

RESOLUTION 5A
The IAU therefore resolves that "planets" and other bodies in our Solar System, except satellites, be defined into three distinct categories in the following way:

(1) A "planet" [footnote 1] is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape [footnote 2] , (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.

(3) All other objects [footnote 3] except satellites orbiting the Sun shall be referred to collectively as "Small Solar-System Bodies".


Footnote 1: The eight "planets" are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

Footnote 2: An IAU process will be established to assign borderline objects into either dwarf planet and other categories.

Footnote 3: These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies.

RESOLUTION 6A
The IAU further resolves:

Pluto is a "dwarf planet" by the above definition and is recognized as the prototype of a new category of trans-Neptunian objects.

Answer 2

We have detected at least two objects larger then Pluto beyond it, these bodies are cometary in nature and on further consideration it was decided that Pluto was as well, it has an eccentric orbit and is a relatively small ball of ice compared to the other planets.

Answer 3

Pluto’s Not A Planet Anymore



My mother told the most beautiful lies. We could lay for hours and listen to her, my sisters and I, peering into the words, the worlds, like a paperweight. They defied logic, her stories, but were never supernatural.


In the afternoons, we read the bible. We laughed. Mother’s stories were so much more colorful. She told us about the baseball player who pitched a no-hitter on acid. My sister said, “I want to be like that when I grow up.” She told us that the rings of Jupiter were made of gas, and we giggled. She told us the moon tugged on the ocean and then let go, every day, several times a day.


In school, they told us how the earth was made. My sisters and I passed notes that read, “This paper is made from trees.” We were always in trouble.


When mother passed, news came on the radio. “Pluto’s not a planet anymore,” they said. We knew it wasn’t so. Just like when they told us Paul was dead, or John, when we observed the 10 minutes of silence at Yoko’s request.


She sent us a joke, from beyond the grave. That we could believe.

Answer 4

Under the current IAU definition, a planet must:

A) Be sufficiently massive such that its gravity pulls itself into a spherical object
and
B) Clear its orbit around the sun of most debris.

While Pluto satisfies A), it does not satisfy B). There are many, many small asteroid-like objects in the Kuiper Belt near Pluto's orbit.

Answer 5

1. Pluto is smaller than what scientists think of when defining "planets"

2. It has a weird orbit that's closer to the kind of orbit comets follow.

3. They are discovering, or expect to discover other "Pluto-sized" rocks in the outer solar system, and have no intention of declaring them all "planets"

4. Also several points others have made are also correct.

Answer 6

A planet USED to be anything with the gravitational power to pull its self into a ball, BUT Pluto is...ugly, its moon its almost its size and makes it wobble, it is VERY small and if we let it keep its planet status then when we moved into the rest of the universe we would find a inconvenient number of "planets" so we added to the definition a planet must be the dominant body in its region of space.

Answer 7

Pluto was never a "plant" to begin with

Answer 8

Astronomers recently defined a planet as celestial body that (a) is in orbit around the Sun, (b) has a nearly round shape, and (c) has cleared the neighborhood around its orbit. Pluto is relatively round and orbits the Sun, but it does not meet the criteria because its orbit crosses Neptune's orbit.

It is one of many thousands of new objects found in the Kuiper belt, and is now considered a "dwarf planet".

Answer 9

Pluto was never a plant, nor are there many plants in space, anyway

Answer 10

apparently pluto is so small and so out of place in the solar system as well as the fact it doesn't have a definitive orbit around the sun makes in no longer a planet