Researchers have discovered, with the help of citizen scientists, about 100 cool worlds that are close to our sun. These are so-called brown dwarfs. Some objects are even among the coolest to be uncovered so far.

Brown dwarfs

A brown dwarf has a mass smaller than the mass of a star, but much larger than that of a gas giant. Because brown dwarfs form in the same way as a star, but are too small to achieve nuclear fusion, brown dwarfs are also called failed stars. It means they don’t have enough mass to ‘ignite’ and start shining like other stars. At the same time, that also makes it difficult to track them down. That’s why astronomers are looking for brown dwarfs mainly in the region around the sun.

Discovering and characterizing objects in the night sky is fundamental to our understanding of our place in – and the history of – the universe. But that’s not so easy. Astronomers, for example, are still trying to map our close neighbors. However, they do not do so alone. They receive help from as many as 100,000 citizen scientists. Thanks to the keen eye of these volunteers, more than 1500 cold worlds have been discovered near the sun. And even now, they’re diligently digging through trillions of telescope images to discern subtle movements of brown dwarfs and planets. And that’s sorely needed. Despite today’s technology, machine learning and supercomputers, there is still no good substitute for the human eye to recognize moving objects on telescope images.

Temperature

The hard work is paying off. Because now astronomers are presenting the discovery of about 100 cool brown dwarfs near our solar system. Using NASA’s Spitzer space telescope, the team was able to accurately estimate the temperature on these worlds. And it shows that some objects are among the coolest we know. These brown dwarfs are approaching the earth’s temperature, which means they are cool enough to accommodate water clouds. And that’s interesting. Brown dwarfs are thought to cool down as they age. It means that their temperature is first comparable to that of stars. Then they cool down further and further to temperatures of planets and eventually completely extinguish. The new discovery of cool brown dwarfs confirms this theory.

It’s a special discovery. Because although this kind of cool objects has long been hypothesized, researchers have failed to find them. The discovery therefore includes a missing link within the population of brown dwarfs. “These cool worlds provide new insight into the formation and atmospheres of planets outside the solar system,” said study leader Aaron Meisner. “This collection of cool brown dwarfs also allow us to accurately estimate the number of worlds that roam interstellar space near the sun.”

Uncharted territory

Thanks to the study, we are getting to know more and more about our own ‘neighborhood’; the area around our sun. “This study is proof that our ‘solar district’ is still uncharted territory,” says Jackie Faherty. There’s probably a lot to discover here. The discovery of the 100 new brown dwarfs is at least an important step to learn more about this area. Moreover, the study proves that citizen scientists are excellent astronomical cartographers. “By making archival data public and easily accessible, people with a fascination for astronomy can make a real contribution to science and understanding of the universe,” says researcher Chris Davis. And that’s all citizen scientist Jim Walla can agree with. “It’s great to know that our discoveries are now counted among the sun’s neighbors and will be the target in future research,” he said.

Moreover, we will soon be able to count on more discoveries. Because the search for rare objects in large datasets is also one of the objectives of the upcoming Vera C. Rubin Observatory. This observatory is currently under construction in the Chilean Andes and will be fully operational from 2022. This telescope will, among other things, observe the outer regions of our solar system and will image the visible sky from the southern hemisphere every three nights for ten years. This will provide a huge amount of data that will enable new ways of astrophysical research. Moreover, this will also shed new light on this now unknown vast area.