A ‘yes’ would truly seem epoch making. But in reality .. this really isn’t a question of scientific worth. Mercury, Venus, Mars, Jup and Saturn were known for a long time. Hershel discovered Uranus in the 1700s, JG Galle discovered Neptune after a few had predicted the existence of such a planet thro calculations and CW Tombaugh added Pluto to the list in 1930. Pluto has been and remains a celestial body with an identity crisis. ..To be (a planet) or not to be?. ‘Planet’ is a loosely defined term with many eminent astronomers having their own views (shape,size,composition,orbit properties are popular criteria). Pluto has had its own opponents, but has made its way to our School Text Books as the ninth planet. And the rest of the eight fellows.. they are in better placed…. They are all BIG..by pluto’s standards.(alright…i know mercury is small.. but it is part of the old ‘planet’ listing… enrolled much before we started measuring sizes and distances!) . Mike Brown puts down this bigginess condition in a scientific way here.(he lists other conditions too). This debate, however, was not very prominent in the public domain. For the layman..we have always had nine planets.(Brown’s page was made for Sedna)
The debate was pushed into public glare last year following the discovery of Sedna by Brown and his team.(see press release) Brown categorically rejected the possibility of Sedna being called a planet. Now, with the yet to be christened 2003 EL61(the object touted as the tenth planet these days), the debate is back in focus. The discovery was announced by Brown (again!) and his team and this time around..they apparently insisted on it being called a Planet. There is a lot of confusion surrounding this discovery. The number of interesting objects actually discovered and the nature of the press releases are being speculated by various pple on the internet. But even assuming that all is fine with the discovery and if we indeed have an object of the claimed size ….do we call it a planet?
It is important to realise that with modern telescopes , vast and unexplored regions of our cosmic neighbourhood are now accessible to us. So, new discoveries are bound to be made. Ofcourse, we will cheer them whenever they are made. Sedna and this latest discovery fall in this domain and full marks to Brown and his team for their fantastic job. Such discoveries require great patience and meticulous observations. More will probably follow.These are times when even graduate text-books get left behind by new discoveries(Observational Astronomy never had it better!). We will understand more about the new objects in terms of their sizes, orbit, composition etc in the future. Though we may not know these things to a great accuracy, these are well defined attribites.. ie when I ask “What is the diameter of Sedna?”.. there is no inherent ambiguity in the question. On the other hand, “Is xxx a Planet?” is an ill-posed question and a yes/no answer may not always be possible. It is time school text books are rewritten.. agreed. But not with an extra planet…. but with a clarification that there is nothing exact about something being a ‘planet’.Much remains to be understood about ‘Planet’ formation and there is no fundamental reason for us to pre-suppose the size range in which ’round’ objects revolving around the sun fall. Lets us treat these discoveries for what they are .. path-breaking advances into a previously unknow zone and avoid this rant about things being ‘called’ a planet. This isn’t a debate of worth!