In April 2019, the Event Horizon Telescope produced the first-ever image of a black hole. The object, located in the center of the galaxy M87, was given the Hawai`ian name of Pōwehi. Its image appeared as a ring with a bright crescent edge, produced by photons orbiting around the black hole. To make these images, this unique telescope uses a technique known as Very Long Baseline Interferometry, which combines radio signals from multiple telescopes around the world. Two Maunakea observatories – the James Clerk Maxwell Telescope and the Submillimeter Array – are a part of this world-wide telescope. Now researchers have returned to data stored in early attempts at this experiment, and discovered that the ring is moving with time. While the earliest efforts could not produce an image, the team used state of the art statistical methods to figure out the shape and size of the ring, right back to 2009. As the gas falls onto a black hole, it heats up to billions of degrees and becomes turbulent in the presence of magnetic fields, varying like waves on the ocean. The “wobble” that the researchers saw in the data over the past decade tells us about how gas is flowing around the black hole.
Read more, in the JCMT press release and the SMA press release.