New research, that was presented at the National Astronomy Meeting at the University of Hull on 6 July 2017, suggests that our galaxy contains as many as 100 billion brown dwarfs.
Brown dwarfs are celestial objects that just didn’t have quite what it takes to become a fully-fledged star. Brown dwarfs are too hot and big to be considered planets, but at the same time they are too small to be stars. Brown Dwarfs are a result of processes that normally lead to the formation of stars but because they lack the mass to sustain stable hydrogen fusion at their cores, the formation is never completed. Astronomy is a harsh industry – in 2006 it demoted Pluto from a Planet to a Dwarf Planet – so it’s not surprising to find out that Astrologists often refer to brown dwarfs as “failed stars”.
This discovery came about when researchers Aleks Scholz from the University of St. Andrews and his colleague Koraljka Muzic from the University of Lison began investigating the density of brown stars to stars in star forming regions known as clusters. The two started researching this when one of the clusters, NGC 133, which is 1500 light-years-away featured half as many brown dwarfs as stars. This figure seemed unusually high to the two researchers – so to get a better sense of the brown dwarf formation rate, within clusters of varying densities – they embarked on a search of brown dwarfs in more distant, far denser star forming region known as RCW38.
The RCW38 cluster again showed that there were half as many brown dwarfs as stars. “We’ve found a lot of brown dwarfs in these clusters,” said Scholz in a statement. “And whatever the cluster type, the brown dwarfs are really common. Brown dwarfs form alongside stars in clusters, so our work suggests there are a huge number of brown dwarfs out there.” This implies that the formation and frequency of brown dwarfs have very little to do with the composition of the star clusters. By comparing brown dwarf formation in two very different clusters—one with a low density of stars and another with a high density—the Scholz and Muzic demonstrated that the stellar environment isn’t necessarily a factor that regulates the ability of a star forming region to produce these objects.
The numbers in the new paper make sense given that stellar objects are more abundant in the galaxy. However, whilst this is an exciting discovery, it is important to note that this paper has been yet to appear in a peer reviewed science journal – so we will have to wait until it has been approved before we can 100% confirm that our galaxy is filled with these free floating ‘failures’.