Free Astronomy Magazine July-August 2019

32 JULY-AUGUST 2019 SPACE CHRONICLES by NASA/ESA Disparity in Hubble Constant calculations is not a fluke A stronomers using NASA’s Hubble Space Telescope say they have crossed an impor- tant threshold in revealing a dis- crepancy between the two key techniques for measuring the uni- verse’s expansion rate. The recent study strengthens the case that new theories may be needed to explain the forces that have shaped the cos- mos. A brief recap: The universe is getting bigger every second. The space between galaxies is stretching, like dough rising in the oven. But how fast is the universe expanding? As Hubble and other telescopes seek to answer this question, they have run into an intriguing difference be- tween what scientists predict and what they observe. Hubble measurements suggest a faster expansion rate in the modern universe than expected, based on how the universe appeared more than 13 billion years ago. A ground-based telescope's view of the Large Magellanic Cloud, a satellite galaxy of our Milky Way. The inset image, taken by the Hub- ble Space Telescope, reveals one of many star clusters scattered through- out the dwarf galaxy. [NASA, ESA, A. Riess (STScI/JHU), and Palomar Digitized Sky Survey]