Why do they not consider pluto as a planet now?

Answer 1

G'day Rohini karthikeyan,

Thanks for your question.

Pluto is now considered to be a dwarf planet.

There are three main conditions for an object to be called a 'planet', according to the International Astronomical Union resolution passed August 24, 2006.

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 neighborhood 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.

I have attached sources for your reference.

Regards

Answer 2

Pluto was discovered in 1930 by a scientist called Clyde Tombaugh. At that time, because there were no powerful telescopes to see it, Pluto was thought to be bigger than earth. But when powerful telescopes became available later, they showed that it was much smaller than our own moon.


Pluto’s diameter is 2,360 km or 1,467 miles, but our moon’s diameter is 3476 km or 2,140 miles. Pluto is also egg shaped and its orbit cuts across Neptune’s.

But the reason for sending Pluto out from the planet group is not exactly this. Since 1990, scientists have discovered a lot of smaller objects in the Kuiper Belt and three years ago, they found an object much bigger than Pluto. It has no names, so the scientists of California University, who were the first who saw it, called it 2003UB313.

After this object was discovered, astronomers asked an important question: if there is an object bigger than Pluto in the Kuiper Belt, then is it right to call Pluto a planet? So, they felt that it is only correct to include it with the objects in the Kuiper Belt.

The International Astronomical Union (IAU), which is the world’s largest group of scientists observing space, finally decided to discuss the matter in their special meeting, which was conducted in the city of Prague last month.

The scientists had two choices. They should exclude Pluto and declare that there are only eight planets. Or they should include 2003UB313 along with two more objects and make the number of planets as 12. When they sat for the meeting, there was tension all around. Nobody, not even the scientists, could say at that time what would happen to Pluto.

In the end, the scientists have created certain rules for planets. What are they? First, a planet must circle the sun. It must be large and round shaped and it must clear other objects from its orbit. Since Pluto did not match these rules, they decided to exclude it from the planet group. Along with two other icy objects in the Kuiper Belt, Pluto is now called a ‘Dwarf Planet’. Yes, many of you are asking what is a ‘Dwarf Planet’, right?

Just like shorter boys are separated in class, Pluto is also separated from the eight big ones and joined with the smaller objects. These smaller objects can’t be compared with the big ones, but then, they also circle the sun. So, scientists have chosen a different name for them– ‘dwarf planets’.

Answer 3

Pluto continues to be designated a Planet by the International Astronomical Union, which is the only body of astronomers on this planet that has the final say in designating astronomical objects.

The problem is that there is very strong interest in providing Pluto with a dual classification because it shares many of the same properties with the recently discovered trans-Neptunian bodies. Historically, there are several presidents for such a dual classification. The minor body Chiron, for example, was initially claimed to be the Tenth Planet, but subsequent studies showed it to be a distant asteroid. Still, it has a distinct coma so it is also classified as a periodic comet among the nearly 10,000 minor bodies with known orbits.

Pluto is a large body and is rightly identified as a planet on this basis alone, with a radius of about 1,700 kilometers. However, in 1996 another large body was discovered beyond the orbit of Neptune, but now has the temporary designation 1996TL66. If one assumes an albedo of about 4%, the radius of this object is some 250 kilometers. There are many dozens of other smaller trans-neptunian bodies that are also known, and this has led the International Astronomical Union to investigate whether Pluto should receive a dual classification as a Planet and as a trans-Neptunian body. It would be the largest of this new population ever detected, and historically the first one discovered.

This does NOT mean that it would be stripped of its classification as a planet, only that it would be the only planet that would also be listed among the minor bodies of the solar system with a designation number near 10,000. The subsequent trans-Neptunian bodies would receive permanent designations beyond number 10,000, so that whenever an astronomer pulls-up a list of these bodies, Pluto would always appear first in the list with the lowest designation number.

It is not more complicated than this, but it is sad how the media, and some astronomers even, have played this story as an attempt at demoting Pluto to merely an asteroid. It is NOT merely another asteroid, it is as genuinely a planet as any of the other 8 large bodies, its just that it also shares MANY attributes with the trans-Neptunian body population, and for technical reasons its membership in this family should also be acknowledged in the catalog of minor planets.

Answer 4

Astronomers do not consider Pluto as a planet now because there are other heavenly bodies which revolve around the Sun like Pluto which are estimated to be 54 in number. If they consider Pluto as a planet, they would also have to include them!!!

Answer 5

the international astronomical union defined three terms "planet", "dwarf planet", and "small solar system body". this does not change anything about the solar system or pluto. it just corrects the mistake of classifying pluto as a planet initially. i don't know how long this will drag on tho. many planetary scientists are not satisfied that the definition is not rigorous enough.

because pluto orbits the sun, is round, does not have an isolated orbit (a bunch of other similar bodies have similar orbits.), and is not a satellite it is a dwarf planet.

i have been waiting for this since i was about twelve. i feel somewhat satisfied. this was the right thing to do, believe me. i don't understand why so many are having such a problem with this.

(1) A "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, and (c) has cleared the neighborhood 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, (c) has not cleared the neighborhood around its orbit, and (d) is not a satellite.

(3) All other objects orbiting the Sun shall be referred to collectively as "small solar system bodies".


look here:
http://en.wikipedia.org/wiki/Kuiper_belt

Answer 6

Purely due to it's size. other than that it has all of the right qualifications. It circles the sun on a regular defined orbit. It also has a satelite(moon which orbits it.) . Some over zealous astronomers claim Pluto's moon is nothing more than a small rock.

Answer 7

Reading any of the dozen or so articles about the Astronomical Society's decision will give you the specifics, but in short:

Pluto is too small.
Too icy.
And, Pluto never managed to claim it's orbital path all to itself (like all of the eight real planets have.)

Answer 8

See the little box above that says "Search for questions"? Type in Pluto and you'll discover that this question has been asked and answered about a ga-zillion times already.

Answer 9

WED (Walter E. Disney) Enterprises Inc. gave him an ultimatum: Either be a planet of be a cartoon character. He chose the money ☺


Doug

Answer 10

Because they are too confused! They are billions of planets up there. They are not able to categorize them so that is why! Before they used to think that there were only nine but every day they discover one or two, can you imagine!