Astronomers have finally solved the long-standing mystery surrounding the brown dwarf Gliese 229 B, discovering that it is not a single body but rather a pair of closely linked brown dwarfs orbiting one another. This incredible discovery has provided new insights into the nature of these substellar objects, while also shedding new light on the understanding of their evolution and dynamics. The two bodies in the system, designated Gliese 229Ba and Gliese 229Bb, orbit each other every 12 days, making it one of the closest binary systems of brown dwarfs ever discovered. This discovery opens up possibilities for new research, especially as it provides additional information on the development and characteristics of such substellar objects, which occupy their place between stars and gaseous giants.

Brown dwarfs are fascinating objects that lie on the boundary between stars and planets, and their mass is large enough for thermonuclear reactions to occur, but not large enough for those reactions to be stable like in true stars. With the discovery of Gliese 229 B in 1995, scientists found that this brown dwarf possesses methane in its atmosphere, which is characteristic of gaseous giants like Jupiter, but not of stars. However, even after nearly 30 years of observations, the brightness of this object remains inexplicably dim considering its estimated mass of 70 times that of Jupiter. Analysis concluded that the reason for this discrepancy in observations is that Gliese 229 B actually consists of two bodies – Gliese 229Ba and Gliese 229Bb – with masses of 38 and 34 times that of Jupiter, respectively. The combined brightness of these bodies now matches what would be expected for a system of this mass.

A team of astronomers from Caltech, led by graduate student Jerry W. Xuan, utilized two key technologies to uncover the binary nature of Gliese 229 B. The first technology involved the GRAVITY instrument on the Very Large Telescope of the European Southern Observatory in Chile, which combines light from four different telescopes and allows for extremely precise distance measurements and spatial resolution. The second technology employed the CRIRES+ instrument, which enables the detection of spectral signatures from both bodies. Using these methods, they succeeded in revealing that one of the brown dwarfs is moving towards us while the other is moving away, indicating an orbital dance of the two bodies orbiting each other every 12 days.

The discovery of the binary nature of Gliese 229 B raises many new questions about how such closely bound pairs of brown dwarfs form. There are various theories suggesting that such pairs may arise within swirling disks of material surrounding young stars. According to one theory, the disk of material fragments into two parts, which then become gravitationally bound after a close encounter. Given that Gliese 229 B is so close to its host star, the theories regarding the formation of such pairs further intrigue astronomers as they suggest the possibility of forming other similar binary systems or even binary exoplanets, which has not been observed to such an extent until now. It is possible that the same mechanisms are at play in forming pairs of planets around other stars, opening new dimensions in the exploration of exoplanetary systems.

Gliese 229 B is not only the first discovered brown dwarf, but now, with the discovery of its binary nature, it has become one of the most fascinating objects in its class. The binary system orbits around a common center of mass, while the entire system orbits around an M-dwarf star that is smaller and cooler than our Sun every 250 years. Their distance is only 16 times greater than the distance between Earth and the Moon, meaning the bodies are extremely close to one another, thus strongly gravitationally bound. This is also important because binary systems like this one can provide crucial data for understanding how more complex systems form in the universe.

According to Xuan, Gliese 229 B has long been considered a prototypical example of a brown dwarf, but we now know that our understanding was incomplete. This discovery is merely the beginning of a new chapter in the study of substellar objects. Future investigations are expected to continue using advanced instruments such as the Keck Planet Imager and Characterizer (KPIC) and HISPEC, an instrument currently under development at Caltech and other laboratories. These instruments will allow for deeper insights into binary systems and assist in understanding the dynamics of these complex cosmic systems.

New discoveries suggest that similar binary systems of brown dwarfs or even exoplanets could be waiting to be discovered. Such systems are not only fascinating in themselves, but they have a profound impact on our understanding of star and planet formation. Given that brown dwarfs are objects that bridge the characteristics of stars and planets, further study of them can help us understand how stellar systems form and evolve. Binary systems of brown dwarfs like Gliese 229Ba and Gliese 229Bb could provide the key to understanding the formation of complex cosmic structures and yield data that will enhance our knowledge of the universe.

The existence of binary brown dwarfs like Gliese 229Ba and Gliese 229Bb demonstrates how advances in technology enable the detection of increasingly subtle and complex phenomena in the universe. These systems present a particular challenge for observation as they often lie at very small distances and their light is dim, but thanks to advancements in telescope technology, we are now able to explore these mysterious objects with greater precision than ever before. The universe is full of undiscovered secrets, and each new instrument developed allows us to see further and deeper than before, revealing the complexity and beauty of cosmic dances like that between Gliese 229Ba and Gliese 229Bb. The first known brown dwarf that is actually a binary system opens the door to the discovery of many similar systems and brings new excitement to the exploration of the universe, allowing us to better understand the dynamics and evolution of substellar objects and their role in cosmological processes.

Source: California Institute of Technology