All disk galaxies rotate once every billion years By Jake Parks | Published: Tuesday, March 13, 2018 Grand spiral galaxy (NGC 1232). FORS/8.2-meter VLT Antu/ESO In a study published March 9 in The Monthly Notices of the Royal Astronomical Society, astronomers announced the discovery that all disk galaxies rotate about once every billion years, no matter their size or mass. “It’s not Swiss watch precision,” said Gerhardt Meurer, an astronomer from the International Centre for Radio Astronomy Research (ICRAR), in a press release. “But regardless of whether a galaxy is very big or very small, if you could sit on...