Cosmologists peering into distant, dust-enshrouded galaxies have found that they are far older and more numerous than previously thought.

Their findings, published Wednesday in the journal Nature, push back the birth of these massive star-creation engines and add more precision to the model of how our expanding universe evolved.

“It doesn’t say when the universe began,” said Joaquin Vieira, an observational cosmologist at Caltech and lead author of the paper. “What it does change is when the most massive galaxies in the universe were born. It pushed it back by a billion years.”

Dusty starburst galaxies are extremely difficult to observe, but astronomers can focus on faint radiation signatures with wavelengths of less than a millimeter. Much of that ability is owed to an antenna array in Chile, known as ALMA, the Atacama Large Millimeter Array.,1201459.story