Astronomers have made a remarkable discovery about the Gliese 229B system, which was previously thought to be a single brown dwarf. It is now revealed to be two closely orbiting brown dwarfs, shedding new light on the formation and nature of these celestial objects that bridge the gap between planets and stars. This finding could help uncover more of these elusive ‘failed star’ binary systems in the Milky Way.
Unveiling the Dual Nature of Gliese 229B: A Surprising Discovery
For decades, Gliese 229B was considered a single, enigmatic brown dwarf – a ‘failed star’ that did not accumulate enough mass to ignite nuclear fusion. However, a team of astronomers from the California Institute of Technology (Caltech) has now revealed that this celestial object is actually a binary system, consisting of two closely orbiting brown dwarfs.
The discovery was made possible by using two powerful instruments at the Very Large Telescope (VLT) in Chile. The GRAVITY interferometer allowed the researchers to spatially resolve Gliese 229B into two distinct bodies, while the CRIRES+ spectrograph detected the unique spectral signatures of the two brown dwarfs, revealing their orbital motion. This groundbreaking finding solves a long-standing mystery about Gliese 229B’s dimness, as the combined light of the two objects is less than a single, more massive brown dwarf would be.
The Elusive ‘Failed Stars’ of Gliese 229B: A Closer Look
Brown dwarfs are fascinating objects for astronomers because they occupy the intriguing realm between planets and stars. These ‘failed stars’ form from collapsing clouds of gas and dust, much like regular stars, but they lack the necessary mass to ignite the fusion of hydrogen into helium in their cores.
Gliese 229B, located 19 light-years away, was the first-known brown dwarf discovered back in 1995, introducing astronomers to this new class of celestial objects. However, even after decades of study, there remained an enigma about this particular brown dwarf – it appeared too dim for its mass.
The newly discovered binary nature of Gliese 229B provides the answer. The two brown dwarfs, designated Gliese 229Ba and Gliese 229Bb, are separated by a mere 3.8 million miles (6.1 million kilometers) – just 16 times the distance between Earth and the Moon. This incredibly close orbit, with the two ‘failed stars’ completing a full revolution around each other every 12 Earth days, explains why Gliese 229B appeared dimmer than expected.
According to the researchers, the two brown dwarfs of Gliese 229B are smaller in radius than the planet Jupiter, making them quite a unique and fascinating sight if they were located in our own solar system.
Unraveling the Mysteries of Brown Dwarf Formation: Insights from Gliese 229B
The discovery that Gliese 229B is not a single brown dwarf, but a tightly bound binary system, raises intriguing questions about how such close-orbiting ‘failed star’ companions form.
One possible explanation proposed by the researchers is that the collapsing cloud of gas and dust that gave birth to these objects could have fragmented into two distinct ‘seeds’ that later became gravitationally bound, leading to the formation of the Gliese 229B system.
This finding also highlights the potential for other such exotic brown dwarf binary systems to be hiding in the Milky Way, just waiting to be discovered. The team now plans to use instruments like the Keck Planet Imager and Characterizer (KPIC) and the upcoming High-resolution Infrared SPectrograph for Exoplanet Characterization (HISPEC) to hunt for more closely orbiting brown dwarf binaries.
As Shri Kulkarni, one of the original discoverers of Gliese 229B, aptly stated, ‘It is so nice to see that almost 30 years later, there has been a new development. Now, this binary system stuns again.’ This discovery not only solves a long-standing mystery but also opens up new avenues for understanding the formation and diversity of these intriguing ‘failed stars’ that bridge the gap between planets and stars.
