I don't understand. How many planets are there in our solar system?

Question

And for extra credit, define the word planet. I understand that the definition of planet has changed in the past year or so. So what are the last four planets?

Answer 1

Eight of the "nine planets" are still planets. Pluto is now a dwarf planet along with Ceres, an asteroid, and Eris, a Kuiper Belt Object.
This is the International astronomical Union's resolution of what a planet is:
(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 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)
shape2 , (c) has not cleared the neighbourhood around its orbit, and (d)
is not a satellite.

(3) All other objects3 except satellites orbiting the Sun shall be
referred to collectively as "Small Solar-System Bodies".


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

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

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

Answer 2

There are officially 8 planets in our solar system. Pluto was demoted to dwarf planet status. The International Astronomical Union is the only organization that can do this kind of thing, and they've come up with an official designation of what constitutes a planet -- A planet is; (1) a celestial body that is in orbit around the Sun; (2)has enough gravity to form it into a spherical shape; (3)has cleared the region of its orbit of other large objects.

Last four planets --
Jupiter
Saturn
Uranus
Neptune

Answer 3

There were nine. Now there is some doubt about Pluto being a planet. Some space nuts are saying it is too small.

The problem is, no one has a definition of what a planet is. Even the British Interplanetary Society is debating this.

The last four planets in the solar system until this latest controversy with Pluto, is Pluto, Neptune, Uranus, and Saturn.

Answer 4

We currently have 8 planets. The former 9th planet, Pluto was later classified as a Dwarf Planet.

Extra Credit.
A planet is any object which orbits around a star, is too small to fuse hydrogen at its core but large enough that its own gravity keeps it round and must have cleared its immediate region of objects of similar size.

Extra extra credit:
Pluto was removed because of Kuiper's Belt, which infact does have a number of objects of similar size too close to Pluto for it to qualify to be considered a planet.

Answer 5

there are 8 planets in the solar system 1-mercury 2-venus 3-earth 4-mars 5- jupiter 6-saturn 7-uranus 8-neptune

Answer 6

There are 8 planets. Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Pluto was a planet but now it has been discovered that it is not.

Answer 7

Well, since Pluto has recently been declassified as a planet, here are the planets in their order going out from the sun:
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus.

Answer 8

there are totally 8 planets. Pluto, ceres and other asteroids are called dwarf planets and they are not considered as planets.

Planets can be defined as any spherical or round shaped thing that orbits the star in a eliptical orbit and with the diameter size more than 3000Kms

Answer 9

well if you want to include pluto its nine planets 8 if you count pluto out, and the definition of planet is is an object in orbit around a star that is not a star in its own right.

Answer 10

There are eight planets (there used to be nine), because when astronauts found a asteroid larger than Pluto, they decided not to have Pluto as a planet, unless they add that asteroid, but they think now that they found this, there could be others that are larger than Pluto out there that we haven't found yet.