Scientists who were studying a catalog of gas clouds detected something strange: five “blue blobs” consisted of young blue stars in the Virgo galaxy cluster.
Unusually, these stars were isolated from their parent galaxies, and their stars were organized in an irregular pattern. Based on those features, the researchers think they’ve discovered a new type of stellar system. A stellar system is a collection of gravitationally bound stars that’s not quite a galaxy but not a common type of star cluster, either.
Even more surprisingly, the blobs were assumed to have little atomic hydrogen gas, a significant ingredient in star formation.
The research team that was directed by Michael Jones, a postdoctoral fellow at the University of Arizona Steward Observatory, reported the presence of heavy metals in the blobs. “This tells us that these stellar systems formed from gas that was stripped from a big galaxy, because how metals are built up is by many repeated episodes of star formation, and you only really get that in a big galaxy,” Jones announced in a statement.
There exists only two main ways gas is removed from a galaxy: tidal stripping, in which the gravitational attraction between passing galaxies draws gas away from them, and ram pressure stripping, which is “when a galaxy belly flops into a cluster that is full of hot gas, then its gas gets forced out behind it,” Jones said. “That’s the mechanism that we think we’re seeing here to create these objects.”