“It took the Event Horizon team two years to reduce and collate the results from their 2017 observations. The data were too voluminous to transmit over the internet, and so had to be placed on hard disks and flown back to M.I.T.’s Haystack Observatory, in Westford, Mass., and the Max Planck Institute for Radio Astronomy, in Bonn, Germany.

The data from the South Pole could not arrive before December 2017, Dr. Doeleman said, “because it was Antarctic winter, when nothing could go in or out.”

Last year the team divided into four groups to assemble images from the data dump. To stay objective and guard against bias, the teams had no contact with each other, Dr. Doeleman said.”