Two ways of measuring how fast the universe is expanding disagree, a puzzle known as the Hubble tension. Tiny magnetic fields ...

Even when you remove the bright stars, the glowing dust and other nearby points of light from the inky, dark sky, a background glow remains. That glow comes from the cosmic sea of distant galaxies, ...

For the first time, scientists have watched high‑energy cosmic rays at work deep inside a thick cloud of gas, not just at its outer surface. Using the High Altitude Water Cherenkov Observatory (HAWC), ...

Roughly 400,000 years after the Big Bang, the universe cooled just enough to allow photons to escape from the primordial cosmological soup. Over the next 14 billion years, these ancient photons—the ...