in a terminal:
sudo add-apt-repository ppa:stellarium/stellarium-releases
sudo apt-get update
sudo apt-get upgrade

from:
http://ubuntuforums.org/showthread.php?p=10252825

The first command adds the stellarium database/software site (called
repository) to you list of sources to download software from
the second updates that list of sources
The third upgrades installed software

So that should effectively update your existing Stellarium install. There
was also a link to dowload the .deb file for Stellerium 0.10.6 which can be
installed in one click.