It began its life when a group of particularly massive stars, producing strong stellar winds, created individual expanding bubbles of hot gas. (sciencedaily.com)
One of the biggest topics in tech this year was the ever - expanding bubble in startup valuations, fueled by an ever - expanding pool of increasingly less qualified investors. (theverge.com)
Their intense radiation heats up surrounding gas to form expanding bubbles. (scientificamerican.com)