I went on the website, and it told me that I needed the Forge Mod Loader, the Micdoodle8 Core Plug-in, and then I downloaded the updated Galacticraft Coremod and the Galacticraft Planets Coremod. I was able to successfully download them all, however when I tried to run the launcher, an error with the micdoodle8 plug-in caused a fatal crash. The instructions on the website told me to put all of the files into the coremods folder. However, the FML setup can't launch the micdoodle8 plug-in, and the updated version does not work. If I remove the older version, then the mod is not there at all. Galacticraft is part of the Tekkit pack, if that's what your original question was.
Edit: I think I just found out the problem: The modpack has been formatted for 1.6.4, but technic has not been updated for compatibility with 1.6.4. I will just have to wait and see then.