not sure if it's Sadna or Sedna or Sadne but anyway, in 2005 NASA found 3 more planets that are much the same as pluto. although they are even more small then pluto, Aris that is really far from pluto got a small moon (which is a rock) and Sanda is the last planet that they found that the Sun gets to it. it's like 5 Billion + Km from the sun.
they are not planets, but they have a mass bigger then an Astroied and now, anything that will pass this mass, will be called "tiny planet".
recoreding to what I read, there are over 1500 planets over there that are much smaller and a little bigger then pluto. it's own of the Kupier Belt Astroids that their mass are a little bigger then a regular Astroid.
if you read National Geographic you will learn much more then you ever did. like that Jupiter have a ring! and Neptune too! they are not as big as Uranus and Saturn but they are there!
Jupiter have 63 moons and 48 has been given names. Saturn have 45+ planets and 35 has been given names. Uranus and Neptune got a lot of moons too, but I don't know the exact amount.
I forgot to tell you about Chars, but you didn't ask.. anyway I told you much then you asked so it's a small rock, that have a shape of a Planet and it's stuck in the Astroid filed between Mars and Jupiter.
the three planets are not a pard of our Sol System, we only have 8 that are planets but they will always find some new planets! they are countless!
anyway, if anyone got any comment to say about it, because it's what I remember and I'm not sure! so you are welcome to disagree