136199 Eris and 134340 Pluto
Published on Sep 13, 2006 at 6:45 pm.
2 Comments.
Filed under asteroids.
Xena is now Eris. The object that caused all the furor over whether or not Pluto is a planet is 2003 UB313. That has been its catalog number. It couldn’t get a name right away, though, so the team that found it nicknamed it Xena. Now it has an official. It is now named Eris. Its moon, which had been dubbed with the nickname Gabrielle, is now Dysnomia.
In the mid 1800’s, there had been a flurry of discoveries of “planets” located between Mars and Jupiter. In fact, in 1850, there were 18 planets. It soon became apparent that these bodies were far too small to count as planets, and that there were so many of them as to consider them planets to be silly. So, after decades of contentious arguments, they were demoted to “asteroids.” However, in more modern terminology, the term “asteroid” is a layman’s term. Astronomers use “minor planet” to refer to these bodies. The International Astronomical Union has a Minor Planet Center that keeps tabs on these things. Astronomers who find an asteroid (or minor planet, as they are officially called) gets to name the body. However, after several asteroids were found, named, and then lost again the rules changed so that you don’t get to name the asteroid until it has been tracked for long enough to know where it is. Generally, this means three or four synodic periods. This avoids the awkardness of someone else finding and naming an already discovered and lost asteroid.
So, when an asteroid is first discovered, it receives a provisional designation that includes the year of discovery and a code that tells when during the year and what order during that period the minor planet was discovered. For example, 2003 UB313 was one of many bodies discovered late in 2003. But, it could not get a real name until it had been observed for a while, the and orbit really nailed down. Also, its planetary status had to be worked out, since asteroids and planets get names in different ways.
Once an asteroid’s orbit has been nailed down, it gets an official minor planet number. This number is sequential. Generally the bigger the number, the more recently discovered, and the smaller the number the longer ago discovered. That is not hard and fast, though, since it only gets the number once its orbit has been nailed down.  For example, the asteroid Hermes was discovered in 1937, but then lost. It was only found again a few years ago, and it has the number 69230. So, the proper way to reference Hermes is 69230 Hermes. Likewise, asteroid 2214 Carol is the 2214th minor planet to get a number, and was found in 1953. Asteroid 1010 Marlene was found in 1923.
Some asteroids have orbits nailed down enough to get their number, but the discoverer either failed to submit a name, or submitted one that was rejected by the committee that has to approve such things.
So, now we have 2003 UB313, with an official number of 136199, and an official name of Eris. Its moon does not get its own number, it has to share a number with Eris. It is officially Eris I, but with the notation that its name is Dysnomia. So, Xena is now 136199 Eris.
The same IAU bulletin that announced the name of Eris, also notes that Pluto is now assigned a minor planet number of 134340 now that it is no longer considered a full fledged planet. So, properly, Pluto is now Minor Planet 134340 Pluto.Â
-Astroprof
Ed Minchau on September 14, 2006 at 10:43 am: 1
The IAU has outsmarted themselves here. Under the rules for naming minor planets, Eris cannot be used as it is too close to the name Eros (asteroid 433). Furhtermore, although they may reject the name Xena, nobody but Mike Brown is allowed to suggest an alternate name until ten years after the discovery of the minor planet. So, until at least 2013, 2003UB313 must still be called either by its numerical designation, or must be called Xena. Eris is out, under the IAU’s own rules.
Now, if they had used a little common sense and accepted the proposed definition of “planet” at the beginning of their meeting this year, then 2003UB313 would be a planet and the IAU could name it whatever they wanted to. By forcing it into the category of Minor Planet however, they are forced to use the rules governing the naming of minor planets, and so we’re stuck with Xena.
Astroprof on September 14, 2006 at 1:56 pm: 2
My understanding from what I have heard Mike Brown say was that \”Xena\” was just a nickname — a sort of joke, and not a serious proposal. I think that it would have been a good name, though! I rather like the whimsical ones. I believe that he did formally propose Eris, though.
But, I totally agree with you that Eris is FAR too close to Eros and so should not have been accepted.