An international team of astronomers has discovered 165 ultra-cool brown dwarfs within 50 parsecs (163 light-years) of the Solar System, opening this class of substellar objects to better and more detailed study than ever before.  

Understanding brown dwarfs is very important. They are the missing link between giant planets and stars, objects that are not big enough to turn on nuclear fusion at their core and start shining.

By studying their properties, astronomers could provide crucial information on how both stars and planets form. The discovery will also help in understanding how brown dwarf themselves come to be. For example, are they born in isolation or are they ejected from a star system after formation?

"Everyone will benefit from the study of brown dwarfs because they can often be found in isolation, which means that we can more easily gather precise data on their properties without a bright star blinding our instruments," said co-author Jonathan Gagné, from the Carnegie Institution of Washington, in a statement.

Although their dimness is an advantage when studying them, it’s also what makes them so difficult to find. These objects are defined as ultra-cool, relative to stars, with a temperature less than 1,930°C (3,500°F). These objects emit most of their electromagnetic radiation in infrared or microwaves, so they are difficult to find with our current instruments.

The Canadian-American team surveyed 28 percent of the sky to discover these 165 new objects, and their research, which is available online and accepted for publication in the Astrophysical Journal, highlights the fact that about a third have very unusual properties so they could have been missed in previous studies.

"The search for ultracool brown dwarfs in the neighborhood of our own Solar System is far from over," said Gagné. "Our findings indicate that many more are hiding in existing surveys."