In the late 1990s, the James Clerk Maxwell Telescope, with its Submillimetre Common-User Bolometric Array (SCUBA), gazed deep into space. The array, built at the Royal Observatory, Edinburgh, in Scotland, looked for submillimeter (100–1000 µm) radiation, and saw significant quantities of luminous matter. 1 Observers reasoned that SCUBA had seen high-redshift (z) analogs of infrared emissions from dust heated by starlight in low-z galaxies.
In April of this year, researchers nailed down the redshifts of 10 of those SCUBA galaxies. 2 Their median z is 2.4, which indicates that the universe was about two billion years old when a typical SCUBA galaxy emitted its light. The SCUBA observations, explains University of British Columbia astronomer Douglas Scott, mean that star-forming dusty galaxies were far more common in the past—by factors of a thousand or more per unit volume—than they are today.
But what was the source of the dust in those...
