Astronomers have unveiled a remarkable cosmic discovery: a pair of brown dwarfs locked in an extraordinary orbital dance around a small star. Previously identified as a single brown dwarf named Gliese 229B, new observations have revealed that it is, in fact, two distinct brown dwarfs orbiting astonishingly close to each other.
The twin brown dwarfs, now designated as Gliese 229Ba and Gliese 229Bb, possess masses 38 and 34 times that of Jupiter, respectively. Situated approximately 19 light-years from our solar system in the constellation Lepus, they represent one of the rare binary brown dwarf systems known to science.
Brown dwarfs occupy a unique position in the cosmic hierarchy—too massive to be planets but not massive enough to ignite the nuclear fusion that powers stars. “A brown dwarf is an object that fills the gap between a planet and a star,” explained Sam Whitebook, lead author of one of the studies published in the Astrophysical Journal Letters. “Because they can’t fuse hydrogen, they just glow dimly as they cool down.”
What makes this discovery particularly intriguing is the close proximity of the two brown dwarfs. They orbit each other every 12 days at a distance only 16 times greater than the separation between Earth and the Moon. Such a tight binary system of brown dwarfs is exceedingly rare, with only one other known pair exhibiting similar characteristics.
The initial discovery of Gliese 229B in 1995 marked a significant milestone in astronomy, confirming the existence of brown dwarfs. However, anomalies in its observed mass suggested there was more to uncover. “Some models predict that objects with masses above 70 Jupiter masses fuse hydrogen and become stars, which was clearly not happening here,” noted astronomer Jerry Xuan, lead author of the study published in Nature.
The revelation of Gliese 229B being a binary system not only solves this mystery but also provides valuable insights into the complexities of star formation. “We still don’t really know how different brown dwarfs form, and what the transition between a giant planet and a brown dwarf is,” Xuan added. “This finding shows us that brown dwarfs can come in configurations we were not expecting.”
As astronomers continue to explore the cosmos, discoveries like these expand our understanding of the universe and the myriad celestial objects within it. The twin brown dwarfs of Gliese 229B invite scientists to rethink existing models and remain open to the surprises that the vast expanse of space has to offer.
Reference(s):
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