Free Astronomy Magazine March-April 2024

MARCH-APRIL 2024 by NOIRLab − Yuanyuan Zhang & Josie Fenske A unique insights into the acceleration of the Universe I n 1998 two separate teams of as- trophysicists, using telescopes at the US National Science Founda- tion’s Cerro Tololo Inter-American Observatory (CTIO) and Kitt Peak National Observatory, both Pro- grams of NSF’s NOIRLab, discovered that the Universe is expanding at an accelerating rate. This phenomenon is attributed to a mysterious entity called dark energy that makes up about 70% of our Universe. The dis- covery came as a surprise to astro- physicists who, at the time, ex- pected the Universe’s expansion to be slowing down. This revolutionary discovery was achieved with observations of a par-