I have installed this on two identical machines from the repository and have the same issue on both: the Celestia splash screen appears and the file check feedback scrolls by in the splash picture, but the software never actually loads and does not produce an error. Perhaps have a look at that package?
Getting this error from the command line:
celestia: symbol lookup error: /usr/lib64/libgtkglext-x11-1.0.so.0: undefined symbol: GTK_WIDGET_NO_WINDOW
Compaq Presario 900Z (AMD Athlon MP, 1.5 GHz, 2 GB RAM, 30 GB HDD) - VL 6.0 Standard
Gateway Laptop (Celeron M 1.60 GHz, 1 GB RAM, 80 GB HDD) - VL 6.0
2 x Homebrew PCs (AMD Phenom II X4 965, 4096MB RAM, 500 GB SATA HDD, ATI Radeon HD 5700, ASUS M4A79XTD EVO) - VL 7.0-64