Fermi Sees the Moon in Gamma Rays

The image is broken up into a grid of eight panels. The first panel has text that reads: “Fermi Images the Moon. These images show the Fermi mission’s improving view of the Moon’s gamma-ray glow. Brighter colors correspond to greater numbers of gamma rays above 31 million electron volts, tens of millions of times the energy of visible light. At these energies, the Moon is actually brighter than the Sun. The glow comes from cosmic rays, particles that constantly bombard the lunar surface. The Moon has no magnetic field, which would screen out lower-energy particles. So instead they strike and interact with the surface, which produces gamma rays. Credit: NASA/DOE/Fermi LAT Collaboration.” The first panel also includes a visible-light image of the Moon, which is small in the center of the panel. The subsequent panels are labeled 2 months, 4 months, 8 months, 16 months, 32 months, 64 months, and 128 months. Each shows a bright yellow region in the middle surrounded by a haze of orange that fades into light red at the edges of the image. The first image is extremely pixelated, with the the central circle coming into more focus with each subsequent image.
NASA/DOE/Fermi LAT Collaboration
CreditNASA/DOE/Fermi LAT Collaboration
Historical DateAugust 19, 2019
Language
  • english

These images show the steadily improving view of the Moon’s gamma-ray glow from NASA’s Fermi Gamma-ray Space Telescope. Each 5-by-5-degree image is centered on the Moon and shows gamma rays with energies above 31 million electron volts, or tens of millions of times that of visible light. At these energies, the Moon is actually brighter than the Sun. Brighter colors indicate greater numbers of gamma rays. This image sequence shows how longer exposure, ranging from two to 128 months (10.7 years), improved the view.