Now Joanna Pietrowska of the University of Cambridge, who recently presented a study at the Virtual National Astronmy Meeting, finally has an answer to a question that was lingering for decades. Astronomers had not previously been confounded by what holds back star formation in some galaxies, known as quiescent galaxies, which still produce stars but hardly anywhere near as fast as those that see much more action. “The transition between a regular star-forming galaxy and one which is no longer forming new stars is an incredibly complex process,” she told SYFY WIRE. “It involves a change galaxy structure and dynamics, which leads to a broad range of relationships observed between different galactic properties and decreased star formation.”