Why is Pluto a sub planet?

Answer 1

it has a moon and only planets have moons

it is definitely not a planet for a couple of reasons.

1. It's planetry orbit crosses Neptunes orbit which means it does not qualify as a planet.
2. It's way too small to be a planet, unlike most other planets which are spherical and a lot bigger.

scientists have therefore classified it as an dwarf planet.

Answer 2

Pluto was a planet when it was discovered in 1930, since the criteria for being a planet was any largish body in direct orbit around the sun. More planets like Pluto were discovered in more recent times, of similar size and distance, maybe a bit further out. We either had to keep adding planets to the list, or re define what a planet was. In 2006, they decided to reclassify what a planet was, one criteria is that a planet has to be big enough to have cleared most of it's orbit from other bodies. Pluto has not done this, but all other eight remaining planets have. So now we have just stuck to eight planets. In 2006, Pluto was reclassified to a dwarf planet.

Answer 3

Short answer: Pluto is too small, doesn't have a nearly round shape (hydro-static equilibrium), and has become gravitationally dominant.

Pluto became reclassified as a dwarf planet after the discovery of Eris in January 2005. Some astronomers called Eris our Solar System's "tenth planet" when it was first discovered. After a lot of discussion, astronomers decided to make up a new category for objects like Eris. That is where the idea of dwarf planets came from. When the category was created, several other similarly sized solar objects were placed in the category along with Pluto and Eris, including Charon - Pluto's moon, or twin planet depending on how you want to classify it, Ceres - the largest asteroid in the asteroid belt between Mars and Jupiter, Makemake - a Kuiper Belt Object that is usually further out than Pluto, and Haumea - a Kuiper Belt Object even further out than Pluto.

Answer 4

Answer:

A planet's gravity must be strong enough to pull it into a spherical shape (hydrostatic equilibrium). Pluto satisfies this requirement. A planet's primary must be a star. Pluto sort of qualifies in this category, though actually Pluto and Charon coorbit each other. Pluto's two smaller moons clearly orbit the Pluto/Charon pair.

Finally, a planet must have cleared most of the debris from its orbit. Pluto fails in this category. Thus it joins the other dwarf planets, Ceres (which was called a planet longer than Pluto was), and Eris, which is larger and more impressive than Pluto. Makemake and Haumea are two more of our solar system's dwarf planets. Sedna, Orcus, and Quaoar might also qualify as dwarf planets.

Original Answer:

It is a dwarf because it is very small, smaller than the earth's moon. Astronomers no longer refer to it as a planet. It also is not comprised of typical planetary materials. Pluto consists of the same stuff of which comets are made, predominantly water ice and dry ice (frozen carbon dioxide), with a smattering of organic debris, unlike all other planets.

Answer 5

With the improved ability of modern telescopes such as the Hubble Space Telescope and the Keck Observatory's telescope on Hawai'i, scientists were able to find several small objects in the outer solar system which, their discoverers hoped, would be designated the "Tenth Planet".

In 2006, the International Astronomical Union took up the issue of "what is a planet?" Strange, perhaps, that the question had never been debated, but here it was. The IAU came to the (very controversial!) determination that a "planet" had to meet three criteria:

• It had to orbit the Sun, not another planet.
• It had to have sufficient mass to have achieved "hydrostatic equilibrium", meaning that it had enough gravity that it crushed itself into a sphere.
• It had to have "cleared the area of its orbit" of other mass.

Objects that met the first two criteria but not the third would be called "dwarf planets".

Pluto, orbiting in the inner Kuiper Belt, was accompanied by other massive bodies; it had not 'cleared the area of its orbit'. Ceres, formerly considered to be the largest of the asteroids, was also re-categorized as a "dwarf planet", and three newly discovered Kuiper Belt objects also met this description, and were named Eris, Haumea and Makemake.

As I said, the decision was somewhat controversial; some astronomers claim that by this definition, Earth itself would be a "dwarf planet"! Further meetings of the IAU will certainly revisit this discussion, and they may change their minds again.

Answer 6

In 2006, the International Astronomical Union (IAU) declared standards for what a constitutes a planet. According to their new standards, Pluto is a 'dwarf planet", along with four other small objects in the solar system that had been nominated as the 'tenth planet".

Answer 7

We know a lot more about Pluto than we did when Pluto was discovered. Astronomers made the decision to call Pluto a dwarf planet now that we see how small it is.

Answer 8

its not little a frigin dwarf and because space guys said that it didnt make specificationss