Brown dwarfs are celestial balls of gas that never got quite massive enough to become stars.
With masses between those of stars and gas giants like Jupiter, the gravitational pressure of their interiors isn’t strong enough to support hydrogen fusion – the reaction that causes stars like our Sun to shine.
As you might expect, this means that they’re incredibly faint and difficult to detect. Many could be in our own cosmic backyard, even closer to us than the closest known star (Proxima Centauri) without us even being aware of it!
Now, with a new citizen science project, Backyard Worlds: Cool Neighbours, anyone with a phone or computer can be the first to spot an undiscovered brown dwarf.
Brown dwarfs are just massive enough to fuse deuterium – an isotope of hydrogen containing a proton and a neutron in its nucleus – that is easier to fuse together due to its higher mass. As a result they emit only a tiny amount of light and mostly in the infrared spectrum, which isn’t visible to the human eye but can be detected using specialised telescopes.
In the project, citizen scientists search for brown dwarfs in the images taken by NASA’s Wide-field Infrared Survey Explorer (WISE) telescope, which may appear as small dots moving across a field of otherwise static stars.