This unusual view of the Moon, made with the Green Bank Telescope (GBT), shows the glow from the Moon’s heat revealing features undetectable to an ordinary telescope that sees only reflected light. This image was made using a new, extremely sensitive radio camera called MUSTANG-2, which detects high frequency radio waves, and the GBT, the world’s largest fully steerable radio telescope. The wavelength of the radio waves detected by the camera is about 3.3mm (a frequency of 90 GHz), which makes it able to measure the temperature of the Moon as if it were sticking a thermometer into its surface.
In this thermal image, the Moon’s North Pole points toward the upper left, and the Sun’s illumination comes from the upper right. We can see the patterns of some of the vast dark plains, or maria, created by enormous lava flows billions of years ago. Ordinarily, when we look at the Moon in reflected sunlight, these maria give the Moon its distinctive pattern of dark patches, but in the MUSTANG-2/GBT image some appear bright, which means that they are warmer than their surroundings. One of these bright maria just to the upper right of center is the Sea of Tranquility, the landing site for the Apollo 11 mission.
Many craters are also visible, but these craters look very different than they do in the optical photographs that we are used to. The normally prominent rays emanating from the Tycho crater (near bottom center) are almost entirely absent because they are formed from compositional differences that do not have a distinct temperature signature. Scientists may use images like this to learn more about the Moon’s geologic history.
The level of detail in this new image of the Moon is made possible by the high angular resolution of the MUSTANG-2 camera (9 arcseconds) which can discern features as small as 16km (10 miles) on the Moon’s surface. Because of the extreme sensitivity of this 223-pixel bolometer camera, in use with the giant collecting surface of the 100-meter Green Bank Telescope, it took less than 40 minutes to make this image.
The MUSTANG-2 camera was developed by the University of Pennsylvania in collaboration with the Green Bank Observatory and the National Institute of Standards and Technology, the National Radio Astronomy Observatory, the University of Michigan, and Cardiff University. The MUSTANG-2 team is supported by the National Science Foundation (1615604), the Mt. Cuba Astronomical Society, and the University of Pennsylvania.
The Green Bank Observatory is a facility of the National Science Foundation and is operated by Associated Universities, Inc.