Why is Pluto out of the solar system?

Answer 1

its because pluto is really far from other planets & sun.
its orbit path exceeds the solar system boundary.

Answer 2

Pluto has been voted off the island.

The distant, ice-covered world is no longer a true planet, according to a new definition of the term voted on by scientists.

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"Whoa! Pluto's dead," said astronomer Mike Brown, of the California Institute of Technology in Pasadena, as he watched a Webcast of the vote. "There are finally, officially, eight planets in the solar system."

In a move that's already generating controversy and will force textbooks to be rewritten, Pluto will now be dubbed a dwarf planet.

But it's no longer part of an exclusive club, since there are more than 40 of these dwarfs, including the large asteroid Ceres and 2003 UB313, nicknamed Xena—a distant object slightly larger than Pluto discovered by Brown last year.

"We know of 44" dwarf planets so far, Brown said. "We will find hundreds. It's a very huge category."

A clear majority of researchers voted for the new definition at a meeting of the International Astronomical Union (IAU) in Prague, in the Czech Republic. The IAU decides the official names of all celestial bodies.

The tough decision comes after a multiyear search for a scientific definition of the word "planet." The term never had an official meaning before.

What Is a Planet Today?

According to the new definition, a full-fledged planet is an object that orbits the sun and is large enough to have become round due to the force of its own gravity. In addition, a planet has to dominate the neighborhood around its orbit.

Pluto has been demoted because it does not dominate its neighborhood. Charon, its large "moon," is only about half the size of Pluto, while all the true planets are far larger than their moons.

In addition, bodies that dominate their neighborhoods, "sweep up" asteroids, comets, and other debris, clearing a path along their orbits. By contrast, Pluto's orbit is somewhat untidy.

Answer 3

Pluto is still in the solar system.
When discovered, Pluto was thought to be quite big (bigger than Earth) and behaving 'like a planet', that is having cleared its area of space, affecting other objects in its area and even having effects on orbits of other planets.
In fact, its discovery comes from a search for something affecting the orbit of Neptune.
Now, we find that it is quite small and there are many other similar objects on similar orbits, with similar properties.

The same thing happened in 1850.

In 1801, Ceres was discovered, after a search to find the 'missing' planet between Mars and Jupiter. It was called a planet. Three more were quickly discovered, but after that no more for almost 50 years. Astronomers were happy that there were 4 planets between mars and Jupiter (after all, that is a lot of space).

Then Astraea, then a whole bunch more and all of a sudden, there were dozens, then hundreds, then thousands (millions?). So, a new class of objects was created: asteroids (also called minor planets). Ceres and the other three planets lost their status and joined the ranks of the minor planets.

Same thing just happened. Pluto is now at the head of a new class of objects called 'dwarf planets'

(Pluto is not even the biggest of these, only the 'oldest known' -- if it were an artist, it may have had itself called, for a while: 'the Trans-Neptunian Object formerly known as Planet Pluto')

If the trend continues, there may be a new class of objects (Oort planets?) that will be discovered in another 150 years.

When looking at the evolution of planetary systems, some theories consider our solar system as having only 4 planets (the gas giants) and, in some dynamical models, only 1: Jupiter (but these are extreme mathematical cases).
The reason is that only the gas giants have truly stable orbits because their large masses may, eventually (after billions of years) eject the smaller riff-raff from the solar system.
We already know that Pluto was formed differently from a 'normal' planet. It was formed more like a comet (but not quite).

Answer 4

Pluto is excluded from our solar system. Now it is referred to as the 'Dwarf Planet.
1. a planet should be circular or round in shape, much bigger than its satellite.
2. it should orbit around the sun in an elliptical or oval orbit without interference.
whereas Pluto is egg-shaped , same size as its moon, Charon.
Pluto has a circular path which crosses that of Neptune's.
there are other planet like objects found in the Kuiper Belt (where Pluto is located )which are bigger than Pluto.

At present the nature of other bodies are studied to find whether they can be included along with Pluto in the giant planet category.
they are:
Xena, (2003 UB 313 ), Sedna, Quosar,2005FY9, 2003EL61 ----

Answer 5

... It's still *in* the solar system, you know o.O

It's just not classed as a planet anymore, and rightly so. It's tiny; it's moon is about 3/4 the size Pluto is and the gravity between the two makes that the gravity centre of Pluto is outside of it's body; it has a too eccentric orbit, which has an aphelion of nearly twice the length of the perihelion; the perihelion itself lies between the orbits of Uranus and Neptune; the inclination to the sun's equator is over 11° which is nearly twice the inclination of most planets - of which Earth has the most eccentric one of 7°; AND to finish off... : IT HAS NOT CLEARED ITS ORBIT OF SMALL DEBRIS AND OTHER SPACE JUNK!!!!

Once it does that, it might be classed as a planet again - and so would any other object in our or any other solar system that has a hydrostatic equilibrium (it is massive enough to have a gravitational effect on its surface to form a round shape, but not massive enough to - basically - become a star), which is not a sattellite (or, which is in direct orbit around a star) and has cleared all space junk from it's neighbourhood.

Something tells me we might have to wait a couple million years for that.

Answer 6

Pluto is still a member of the solar system, it's just not a full fledged planet anymore, according to the eggheads at the International Astronomical Union. It still has the same orbit, et cetera.

For what it's worth, the Union's vote was very controversial...the full membership didn't participate in the vote, and according to the new rules, other planets could be theoretically 'demoted'.

Answer 7

A couple reasons that Pluto was dropped from the list of planets known in our system are based on it's size and orbit. The orbit that has in more consistant to the orbit that an asteroid who take. The size of Pluto simple lowers it to dwarf planet status or TNO (trans neptune object). I personally must applaud the scientific community for this change. I wouldn't call an apple something other than an apple.

Answer 8

Pluto is still in the solar system. Pluto lost its Planet status as it wasn't considered large enough. There are lots of atroids in the Kuiper belt that are a lot larger than pluto.

Answer 9

IAU decision and the "Great Pluto War"

The debate came to a head in 2006 with an IAU resolution that created an official definition for the term "planet". According to this resolution, there are three main conditions for an object to be considered a 'planet':

1.The object must be in orbit around the Sun.
2.The object must be massive enough to be a sphere by its own gravitational force. More specifically, its own gravity should pull it into a shape of hydrostatic equilibrium.
3.It must have cleared the neighbourhood around its orbit.

Pluto fails to meet the third condition. The IAU further resolved that Pluto be classified in the simultaneously created dwarf planet category, and that it act as prototype for a yet-to-be-named category of trans-Neptunian objects, in which it would be separately, but concurrently, classified.

There has been resistance amongst the astronomical community towards the reclassification, dubbed the "Great Pluto War" by some astronomers.Alan Stern, principal investigator with NASA's "New Horizons" mission to Pluto, has publicly derided the IAU resolution, stating that "the definition stinks, for technical reasons." Stern's current contention is that by the terms of the new definition Earth, Mars, Jupiter and Neptune, all of which share their orbits with asteroids would be excluded. However, his own published writing has supported the new list of planets, as "our solar system clearly contains" eight planets that have cleared their neighbourhoods. Marc W. Buie of the Lowell observatory has voiced his opinion on the new definition on his website and is one of the petitioners against the definition. Others have supported the IAU. Mike Brown, the astronomer who discovered Eris, said "through this whole crazy circus-like procedure, somehow the right answer was stumbled on. It’s been a long time coming. Science is self-correcting eventually, even when strong emotions are involved."

Among the general public, reception is mixed amidst widespread media coverage. Some have accepted the reclassification, while some are seeking to overturn the decision, with online petitions urging the IAU to consider reinstatement. A resolution introduced by some members of the California state assembly light-heartedly denounces the IAU for "scientific heresy," among other crimes. The U.S. state of New Mexico's House of Representatives passed a resolution declaring that, in honour of Tombaugh, a longtime resident of that state, Pluto will always be considered a planet while in New Mexican skies, with March 13th being known as "Pluto Planet Day". Others reject the change for sentimental reasons, citing that they have always known Pluto as a planet and will continue to do so regardless of the IAU decision.

The verb "pluto" (preterite and past participle: "plutoed") was coined in the aftermath of the decision. In January 2007, the American Dialect Society chose "plutoed" as its 2006 Word of the Year, defining "to pluto" as "to demote or devalue someone or something", an example being "as happened to the former planet Pluto when the General Assembly of the International Astronomical Union decided Pluto no longer met its definition of a planet."

Answer 10

Pluto is still in Solar system but it has lost its planet status, because of its small size orbital. Now its a dwarf planet

Answer 11

It is? Since when? I disagree; Pluto is still part of the solar system.

Perhaps you mean, why is Pluto not considered a planet?