There exists a class of spatial body in between stars and gas giant plants known as brown dwarfs. These are essentially failed stars that never had the resources necessary to exhibit nuclear fusion, but they’re too large and hot to be considered planets.
Image Credit: NASA/JPL/Caltech
They’re more difficult to find than stars because they’re extremely dim in comparison. On the other hand, many do emit infrared radiation, which makes it possible to detect them even from thousands of light years away.
Because finding brown dwarfs a hassle compared to finding other objects in the galaxy, an ongoing question of just how many of them exist in our Milky Way galaxy has continued to stump astronomers.
A new study, on the other hand, conducted by astronomers from both the University of Lisbon and the University of St Andrews uses both new and existing surveys to suggest that our galaxy could be home to as many as 100 billion brown dwarfs.
To make the study possible, astronomers from different countries have been surveying star clusters in varying regions of the sky since 2006 to determine how common these objects really are. For consistency reasons, the study considered five different distant star clusters that were both close and distant, between 1,500 to 5,500 light years away, to see if there would be any stark differences.
To their surprise, every star cluster observed exhibited a fairly-consistent number of brown dwarfs. With this data, we can take the number of galaxy clusters we know about and multiply it by the average number of brown dwarfs found in the star clusters that were studied.
"We've found a lot of brown dwarfs in these clusters. 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," said Aleks Scholz, a lead astronomer involved in the study.
The estimates pin the number in between the 25 billion and 100 billion figures, but the researchers also note that their study doesn’t consider the smallest and dimmest brown dwarfs that couldn’t be found, which indicates that there might even be exponentially more out there than the study indicates.
The study concludes that brown dwarfs are far more common than we think. This has implications for our estimates of galaxy mass and star formation in our galaxy and others. It should be interesting to see if any future studies will pick up where this one left off and confirm these numbers indefinitely.
The findings are set to be presented during the National Astronomy Meeting at the University of Hull on Thursday.