A new paper from NASA’s Backyard Worlds: Planet 9 project announces that volunteers have essentially doubled the number of known brown dwarfs, with over 3,000 new discoveries made over the past 10 years since the project began. Brown dwarfs are balls of gas the size of Jupiter, less massive than stars. There’s one for every three or four stars near the Sun.  Although brown dwarfs are common, they can be hard to spot because they shine so faintly compared to stars. Having twice as many brown dwarfs to study allows astronomers a deeper understanding of these elusive objects. Already, this vital new list of brown dwarfs has revealed a new variety of objects – the extreme T subdwarfs and many other rarities , such as ultra-cool objects and a brown dwarf that appears to have aurorae . It has also helped us inventory the distribution of mass in our galaxy and map our cosmic neighborhood .…