The 10th Planet has been downsized…

Tuesday, January 31st, 2006 at 12:45 PM by Administrator

2003 UB313 was announced last summer as the first Kuiper Belt Object bright enough and far enough out to be significantly larger than Pluto. In fact, unless it was 100% reflective, it was almost certainly larger than Pluto in diameter and so many started calling this distant world the 10th planet. The actual size of this world was still up in the air because astronomers were uncertain as to its reflectivity, called by astronomers its albedo. If an object has high albedo, it reflects a lot of sunlight and thus will look brighter than an object of low albedo.

Well, it appears that observations from the Hubble Space Telescope were actually able to resolve 2003 UB313, showing it to be barely bigger than Pluto. To quote the article I’ve linked to “The team’s previous estimates had ranged from 25% larger (on its Web site) to 50% larger (at NASA’s announcement in July).” This Plutonian diameter implies 2003 UB313 has a very high albedo on the order of 92%, high enough to indicate a “fresh icy surface”. With the discovery of icy volcanos on Enceladus a few months ago a though has cross my mind… could it be possible cryovolcanism is at play here. I know that Enceladus has an Albedo very close to 100%, and an icy composition would be expected for a Kuiper Belt Object, but it is still something interesting to comtemplate.

Its also interesting to note how much has been learned about this distant world in just a few months[1] … we now have a good idea as to its size, its mass and some idea of its surface composition.

Linknotes:
  1. Well, Brown’s team had two years longer than anyone else to observe 2003 UB313, but these discoveries have all happened in the few months since the public announcement of the existance of this world. ↩

Posted in Astronomy News

One Response to “The 10th Planet has been downsized…”

  1. SCSU Astronomy » Blog Archive » Super-sizing the 10th Planet again… wrote on 02/2/06 at 11:06 am :

    [...] There is a general rule in science and that you should never trust a single observation. Earlier this week I reported a story that the “10th Planet” 2003 UB313 had been “downsized” with a new diameter estimate just a bit larger than Pluto’s diameter. Now come the millimeter-wave observations… [...]