When is a planet?

Today marks the 9th anniversary of the discovery of Eris, which may be the solar system's tenth planet, but only if you recognise Pluto as a (ninth) planet.  Most people don't. If you believe in the ability to accurately measure the diameter of an object that is 100 times more distant from the sun than we are and one pixel wide, then Eris is 2330km across - essentially the same as Pluto.  It was found on 5th Jan 2005 by comparing sequential images taken of deep space and looking for dots that moved.  The team that made the discovery was led by Mike Brown from the CalTech Palomar Observatory; they were consciously hunting for TNOs (Trans Neptunian Objects) to better understand what's happening at the very edge of the solar system.  Interestingly the actual images were taken on 21st October 2003 but weren't found in the backlog until 15 months later and not announced until 6 months after that.  It's easier to obtain astronomical data than it is to make sense of it, a statement which is true of DNA sequence data of which we have oceans.

You have to store this raw data somewhere until you get round to processing it, and the Palomar team left it on the web-server.  Their web-server was connected to the internet and so was available to anyone who knew where to look and what to look for.  Meanwhile in July 2005 Pablo Santos Sanz a student at the Sierra Nevada Observatory in Spain was analysing their backlog of photographs and discovered the trace of another object on pictures taken in March 2003.  He checked the interweb to see if anyone else had reported his slowly moving dot and came across a note about them, or something close to them,  from Mike Brown. Some judicious googling pulled up the logs from Palomar, so Santos and his boss hurried their report into the Minor Planet Centre to establish priority.  A collaborator of theirs in Mallorca found their dot as far back as 1955 in digitised images from Palomar.

Needless to say, la merda started to fly then.  The Palomar people accused the Spaniards of ripping off their data, the Spaniards suggested that Palomar didn't know what they had in their war-chest.  Things looked murky when the Spanish denied they had seen the Palomar logs, while the Palomar server logs showed that someone had viewed the data from an IP address owned by Sierra Nevada.  And of course, each team had chosen a different name: Ataecina an Iberian  goddess of the underworld or Huamea a Hawaian goddess strongly associated with Mauna Kea where there's another observatory.  These names are decided by the IAU International Astronomical Union a quango which is top heavy with Americans, so you may guess which name was officially registered.  While he was about it, Brown hurriedly announced his discovered of Eris and another smaller object called Makemake (a deity associated with Easter Island) at the same time.  Makemake was discovered just after Easter 2005, hence it's name.  I guess we can be grateful that Eris is named after a minor goddess of the classical Greek world: the Palomar team came within an ace of calling it Xena after a TV series.