Say Hello to our new found planet Sedna in our Solar System in The AnswerBank: Science

There are only 8 planets,pluto was downgraded.

There was not nine anyway, Pluto is not designated as a "proper" planet unlike the 8 "proper" planets.

Pluto is now designated as a dwarf planet and there are now 5 objects that are probably dwarf planets (Ceres, Pluto, Haumea, Makemake, and Eris) though they may not all be dwarf planets.

jake-the-peg

What happened was that an increasing number of objects were being found in the outer solar system - Sedna was just one of them.

http://en.wikipedia.o...ans-Neptunian_objects

It was getting to the point where we were going to be either adding planets on a regular basis or we were going to have to redefine a planet and probably lose Pluto in the process

The International Astronomical Union decided on the latter.

The rule was a planet had to orbit the sun and be massive enough to have a reasonably spherical form.

To these wo they added a further rule that to be a planet an object had to have generally cleared its orbit of other bodies.

This effectively declassified trans-Neptune objects as planets

JonnyBoy12

Question Author

Thanks for your speedy replies, folks but I really do not like people stealing planets from our solar system. I may have to call the Planetary Police if you do this much more. Dwarf planets have feelings too, you know.

My Very Excellent Mother Just Served Us Nine Pizzas

This is a good way to recall your old 9 planets.

jake-the-peg

I'm afraid the IAU *are* the planetary police!

Might I suggest a change of menu?

My Very Excellent Mother Just Serves Us Nachos

Kiki-frog

Jonny - the one I was taught was Many Vicars Eat Mice Just So U Notice Priests.

modeller

Thanks kiki I'll remember that one.

I can't remember what you call that method . Can you tell me ?

modeller

Thanks johny I had missed your method .

JonnyBoy12

Question Author

I am glad you agree that my question is out of this world! I will not insult any of you by saying what planet are you on as clearly you know your stuff.

My Very Easy Method. Just Serve Us Nine Planets!

THECORBYLOON

My Very Easy Method, Just Say U kNow Planets. It's called a mnemonic.

jake-the-peg

It was actually Eris that set the cat amoungst the pigeons because it is larger than Pluto

It was that that lead to Pluto's downgrade otherwise all these would probably have a good case to be planets too

http://en.wikipedia.o...ki/File:EightTNOs.png

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Say Hello to our new found planet Sedna in our Solar System

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