The natural satellite of the Earth does not have a constant color, humanity knows the “bloody moon”, “blue”, “silver”, “cheese” and many other options. And recently astronomers using the most powerful radio telescope ASKAP in Western Australia received another – unique – image of the moon. On it, she appears before us in all the colors of the rainbow and, although this picture seems unreal, in fact it is absolutely accurate.
The secret is simple – the image is formed from data on radio waves reflected by the Moon. Since the human eye cannot see them, the computer has colored the picture, but the radio waves themselves are real from the point of view of physics, so the image is reliable. Moreover, astronomers note that the moon looks much more interesting in the radio range than in the visible spectrum.
The moon reflects radio waves rather poorly, no more than 6% of those incident on it, the rest of the radiation is absorbed and converted into thermal energy, which is re-emitted back. As an example, consider this image from the National Radio Astronomy Observatory in Green Bank, West Virginia (above). During filming, the Sun was to the left of the Moon, so that part is noticeably warmer, as seen in the image.
ASKAP’s work is built on a different principle, here the change in the orientation of radio waves when they are reflected from the lunar surface is recorded. Since it has the shape of a ball, for an outside viewer, the angles of polarization change over the entire visible disc. It is clearly seen that the opposite areas along the edges have identical parameters, and along the lunar limb there is an effect rainbows.