Warnings:

• Use of NASA logos, insignia and emblems are restricted per US law 14 CFR 1221.
• The NASA website hosts a large number of images from the Soviet/Russian space agency, and other non-American space agencies. These are not in the public domain.
• Materials from the Hubble Space Telescope may be copyrighted if they do not explicitly come from the STScI. [1]
• All materials created by the SOHO probe are copyrighted and require permission for commercial non-educational use. [2]
• Images featured on the Astronomy Picture of the Day (APOD) web site may be copyrighted. [3]