Why are the sun and moon not planets please?

Question

Why are the sun and moon not planets please?

Answer 1

First of all, the moon is to small to be a planet.  Secondly the sun is to hot to be a planet.

Answer 2

A long time ago, they were.

The Greek expression "aster planetes" meant: moving star.  

It was used to distinguish the seven special objects in the sky that moved among the rest of the fixed stars.  Sun, Moon, Mercury, Venus, Mars, Jupiter and Saturn -- except that, of course, Greek astronomers would have used the Greek names: Helios, Selene, Hermes, Aphrodite, Ares, Zeus and Chronos.

The word "aster" meant any object in the sky, beyond the atmosphere.  Anything in the high atmosphere was called a meteor.  The study of "meteorology" is the study of what goes on in the atmosphere (in meteorology, clouds are 'meteors').

Aster planetes gave us the word "planet", just like the aster cometes (hairy stars) became "comets".  

When Galileo discovered 4 more moving things (around Jupiter), they were called planets, at first.

When the Sun-centred system (described by Kepler) was finally accepted, the vocabulary was redefined.

The Sun was finally recognized as a star and given the special place at the centre of the "solar system".  The word planet was reserved for objects in orbit around the Sun.

The Galilean planets lost their planet status: a new class of objects was created: satellites (objects in orbit around planets).

The Earth became a planet (even though it was never actually "seen" as moving among the fixed stars -- but it was in orbit around the Sun).

The Moon also lost its planet status and became a satellite.

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1801, a new planet was discovered between Mars and Jupiter.  It was Ceres.  Soon after, three more:  Pallas, Juno, Vesta.  They were all known as planets for almost 50 years.

All of a sudden, after 1850, better telescopes allowed astronomers to discover tens, then hundreds more planets between Mars and Jupiter.

Astronomers decided to create yet another class of objects:  minor planets:  objects in orbit around the Sun, but not big enough to show a disk in a telescope (they "looked like stars" = asteroids).

Ceres, Pallas, Juno and Vesta lost their "full fledged" planet status and became the first minor planets.

When Pluto was discovered, it was called a planet because it was thought to be big.  Now, we know that Pluto is even smaller than our Moon, it is not made like other planets (it is mostly ice), and it is surrounded by other objects of similar size on similar orbits (just like in the 1860s with the asteroids).

This time, a formal definition of planets was created.

This formal definition definitely excludes the Sun and the Moon.

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At some point (a few decades ago) there was talk of calling the Earth-Moon pair a "double planet".  Although there is not a formal, official definition yet, it seems that a pair would be called a double planet if the centre of mass is completely outside both bodies.  In the case of the Earth-Moon pair, the centre of mass is still inside Earth (Earth is so much more massive than the Moon).  Therefore, it is not considered a double planet.

This "confirms" that the Moon is a satellite, not a planet.

Answer 3

The Sun is a star

The moon is a satellite of a planet - earth

Answer 4

Because the sun is a star and the moon has no atmosphere, gasses, nothing to distinguish itself. It's a large rock. Made of cheese.

Answer 5

because they dont orbit a star

Answer 6

your little mind wouldn't be able to comprehend...

Answer 7

the sun - it makes it's own light (it's actually a star) a star can't be a planet too.

the moon - it doesn't revolve around (move around) a star, it revolves around earth.

understand? the other one said you won't comprehend so i explained a little.

Answer 8

Firstly the sun is a star it is just our name for our sun. Secondly the moon has no gases or atmosphere on it. There is also no gravity on the moon. Also the moon does not orbit the sun like allthe planets do it orbits us.

Answer 9

they have a difference. the sun is not like a planet. its a ball of hydrogen which is being converted into helium while this doe snot happen on the earth... the moon is too small to be called a planet and as it rotates around a planet(earth) it is called a satellite!!  

Answer 10

In short, planets are bodies that orbit a star. A moon is a body that orbits a planet.

Answer 11

because they are stars

Answer 12

The sun is a star and does not orbit anything

The moon does not orbit a start instead it orbits a planet, therefore the moon would be a satellite

Sun = Star

Moon = Satellite

(need help with a question) http://answers.yahoo.com/question/index?...

Answer 13

i guess they dont have the prerequists to be called planets

Answer 14

To be a planet, you need to be orbiting a star, be massive enough to be rounded by your own gravity, but not be massive enough to start a thermonuclear reaction.

The sun isn't orbiting a star, and it has a thermonuclear reaction happening inside - hence it's a star itself.

The moon is orbiting a planet (the earth) instead of a star, hence it can't be a planet either.

Answer 15

The moon is the earth's only satellite, it is so called because it orbits the planet earth, the sun is the centre of our solar system, and all known planets rotate around it, due to it's massive gravitational pull.

Earth is about 93 million miles from the sun, the moon is about 1/4 million miles away, from earth, why don't you work out the mass of the sun?

Answer 16

In traditional astrology the Sun and the Moon are not actually considered as planets, but as the "lights" — the Light of the Day and the Light of the Night. They symbolize the two fundamental aspects of that universal Power which ancient philosopher-mystics saw as the dynamic warp and woof of the material world.

Answer 17

The Sun is a star, a body composed primarily of hydrogen and helium, that emit copious amounts of energy generated by thermonuclear fusion.

The Moon orbits the Earth, this is why it isn't a planet.  If Moon was orbiting the Sun alone in our orbit, it would be a planet.

Happy?

Answer 18

Good question. The first thing you should keep in mind is that no scientist can accurately define "a planet". Scientist usually just go by what planets we have and identify their characteristics. The Sun is not a planet because it is a star. A star is a giant ball of collective gases that are held in a gravitational field and produce energy called fusion. Fusion is a special form of energy production that causes atoms, that wouldn't regularly fuse together, to fuse together causing extreme amounts of energy. This fusion happens in every star. If that happened to a planet, it wouldn't exist as a solid.

The moon is not a planet because it orbits a planet already and because technically, the moon is dead. It has no seismic activity, no hot core, no significant magnetic field, and it has no atmosphere of any kind.  

Answer 19

The Sun is a star because it has enough mass and the right composition to sustain fusion reactions inside itself.

The Moon is a satellite/moon because it formed  around a larger, non stellar, body after said body, the Earth, captured and collided with another body, Theia.

Planet is a pretty iffy way of defining what astronomical objects are. In the end astronomers will probably wind up working out some dry classification system that doesn't involve the vagaries of colloquial language.

I'm hoping for one based on mass and composition as the first considerations with origins and orbital relationships as secondary considerations.