They haven't discovered Kuiper Belt Objects bigger than Mars as far as I know. But they have discovered one (UB313?) that is bigger than Pluto.<br /><br />The International Astronomical Union is, as far as I know, hard at work deciding how to find a way of determining how they should go about to find out how they will decide who to invite to a discussion about how they should try to find a definition of the word "planet". It will take time. For now the 9 "classic" planets are officially planets, and the other objects are not classified as planets yet.<br /><br /><br />The problem is to decide where to draw the line between planets and other objects.<br /><br />Some people say we have 8 planets and that Pluto is not a planet, because it clearly has been formed in a different way to the other planets (gas giants) out there. Although if objects as diverse as Mercury and Jupiter both are planets, then Pluto and Sedna and the other large Kuiper Objects could very well be called planets as well.<br /><br />Other say we have 9 planets because a planet is a cultural and historical term, not a scientific one, while others (myself included) say that Pluto and any other large object out there should be classified as planets - which of course leads to the question of what a "large" object is.<br /><br /><br />There are objects ranging in size from dust grains to pebbles, rocks, boulders, mountains and so on all the way up to the planets we know in our solar system. The line has to be drawn somewhere. Every dust grain is not a planet.<br /><br /><br />It has been speculated that the International Astronomical Union will stop using the word "planet" and instead divide them into categories, like "Terrestrial planets", "Gas giant planets", "Minor planets" and that Kuiper Objects (including Pluto) will be in a separate category of planet.<br /><br /><br />Pluto, as mentioned in a previous post, has been confirmed to have 3 moons. Strangely enough, as ever smaller objects are found orbiting Jupiter an <div class="Discussion_UserSignature"> <p><font color="#ff9900">----------------------------------</font></p><p><font color="#ff9900">My minds have many opinions</font></p> </div>