A surprising discovery: strange "blue bubbles" in the night sky turned out to be clusters of young stars.

Five of these blue spots were found in the Virgo galaxy cluster using observations from Hubble and the Very Large Array. It appears to be a new type of stellar system composed solely of young blue stars, arranged in a random fashion. This peculiar arrangement raises the question of how they became isolated from any older stars. They were indeed isolated, as the nearest potential parent galaxy was hundreds of light-years away.

Upon closer inspection, the team discovered even more peculiarities in the blue spots. Spectroscopy revealed that there was very little atomic hydrogen in the systems, which is strange because this is a key ingredient for star formation.

“We noticed that most systems lack atomic gas, but that doesn’t mean there’s no molecular gas,” said Michael Jones, the lead author of the study. “In fact, it must be there because stars are still forming in these systems. The existence of predominantly young stars and a small amount of gas suggests that these systems must have lost their gas quite recently.”

It was also found that the young stars contain a significant amount of heavy metals, indicating that the systems were born within much larger galaxies, where several generations of star birth and death had already occurred. However, their youthful age and isolation from any potential parent galaxies suggested that they lost this gas very rapidly. Thus, astronomers propose that this occurred as a result of a process known as pressure-driven stripping.

The team predicts that ultimately these blue stellar systems are likely to split into smaller ones before spreading further into the Virgo cluster.