Brown dwarf stars are interesting objects. The celestial bodies are failed stars that resemble rogue planets and, as a general rule, have masses that are less than 0.075 times that of the Sun or 75 times that of Jupiter. Size alone would make them difficult to find, but the challenge is compounded by their faint brightness.
Research suggests that there could be as many as 100 billion of these small, dim wanna-be stars hiding all over the Milky Way. But astronomers have actually found that there are about six stars for every brown dwarf in our area of space, making these runts of the proverbial stellar litter even rarer than thought.
All that’s to make a point that identifying brown stars in the sky is no trifle, which makes it all the more amazing that an amateur scientist with no formal training in astronomy upped the catalog with nearly three dozen new brown dwarf systems.
Brown dwarfs are ‘sub-stellar’ objects, meaning they have less mass than a star but more than a planet, and are generally thought to be binary. Now, a citizen scientist from Luxembourg has nearly doubled the amount of known brown dwarf systems in the Sun’s neighborhood.
Frank Kiwy, a software developer, examined the NOIRLab Source Catalog DR2 of the National Science Foundation’s (NSF) NOIRLab, a database of four billion celestial objects, to find brown dwarf companions. His extensive research produced 34 ultracool dwarf binary systems, roughly doubling the number of systems previously identified.
Like stars, brown dwarfs are made when clouds of gas and dust in the space between stars collapse because of their own weight. In main-sequence stars, the core is lit by nuclear fusion, which is caused by the heat and pressure in the core. But some aspiring stars never attain that point. Instead, they attain a stable state before fusion is triggered. Without fusion, these stars don’t give off much light, making it hard for astronomers to see them.
The nearest brown dwarfs are found in the Luhman 16 system, a binary of L- and T-type brown dwarfs located at a distance of around 6.5 light-years. After Alpha Centauri and Barnard’s Star, Luhman 16 is the third nearest star system to the Sun.
More than 2,500 probable ultracool dwarfs were discovered by Kiwy by scanning the data for objects matching the color of brown dwarfs. These, in turn, were examined for indications of comoving companions, and 34 systems containing a white dwarf or low-mass star with an ultracool dwarf companion were discovered.
Zooniverse’s Backyard Worlds: Planet 9 citizen science project’s astronomers, of which Kiwy is a part, previously consulted a global network of more than 100,000 volunteer citizen scientists who examined telescope photos to spot the tiny motion of brown dwarfs against background stars. This helped them detect the brown dwarfs. Although machine learning and supercomputers have evolved, the human eye is still a unique resource when it comes to searching telescope images for moving objects.
“I love the Backyard Worlds: Planet 9 project! Once you master the regular workflow on the Zooniverse project, you can dive much deeper into the subject. So, for example, you can get involved in side projects conducted by members of the science team and join the weekly hangouts with the scientists, which is great fun and always very informative,” Kiwy said in an interview.
“The Backyard Worlds project has fostered a diverse community of talented volunteers,” commented Aaron Meisner, an astronomer at NSF’s NOIRLab and co-founder of Backyard Worlds. “150,000 volunteers across the globe have participated in Backyard Worlds, among which a few hundred ‘super users’ perform ambitious self-directed research projects.”
In addition to being a great example of citizen science, these discoveries could help astronomers figure out if brown dwarfs are more like oversized planets or undersized stars. They could also help them understand how star systems change over time. It also shows how scientists who use astronomical archives and science platforms continue to make outstanding contributions to astronomy.
“If you are curious and not afraid to learn something new, this might be the right thing for you. Just give it a try and you will quickly find out,” Kiwy said.