View of two-thirds of the entire sky with very-high-energy gamma rays observed by HAWC. Many sources are clearly visible in our own Milky Way galaxy, as well as two other galaxies: Markarian 421 and Markarian 501. Some well-known constellations are shown as a reference. The center of the Milky Way is located toward Sagittarius. Credit: HAWC Collaboration The United States and Mexico constructed the High Altitude Water Cherenkov (HAWC) Gamma-ray Observatory to observe some of the most ene...