Can Planets Form Around Brown Dwarfs?

Yes, planets can indeed form around brown dwarfs, a process that shares many similarities with planetary formation in our solar system. The key factor is the angular momentum of the collapsing molecular cloud of gas, which stabilizes the collapse and allows for the formation of planets. The primary difference lies in the insufficient amount of material reaching the center to initiate fusion and turn the brown dwarf into a star.

For instance, our own Sun, although capable of fusion, relies on quantum tunneling effects in its core to sustain it. Similarly, a brown dwarf lacks the necessary mass to trigger this process. Even if planets fail to form through this initial process, stars like brown dwarfs can sometimes capture objects and turn them into planets orbiting around them. This phenomenon was famously elucidated by Stan Peale at UC Santa Barbara, who discovered a planet orbiting a neutron star, a scenario once thought impossible.

Characteristics of Brown Dwarfs

Brown dwarfs, often referred to as 'failed stars,' fall between the mass range of Jupiter and the smallest stars. Most brown dwarfs are only slightly larger than Jupiter, ranging from 10 to 15 times its size, but can be up to 80 times more massive due to their higher density. Although they cannot achieve the fusion required for full stellar status, brown dwarfs can sometimes capture planets.

Planetary Mass Objects Orbiting Brown Dwarfs

Several planetary-mass objects have been detected orbiting brown dwarfs. Examples include 2M1207b, MOA-2007-BLG-192Lb, 2MASS J044144b, and Oph 98 B. These discoveries have statistically increased the probability of finding habitable planets orbiting some brown dwarfs. A notable example is Proxima Centauri b (also known as Alpha Centauri Cb), an exoplanet orbiting within the habitable zone of the brown dwarf star Proxima Centauri, which is the closest star to our Sun and a part of the Alpha Centauri system.

Formation and Characteristics of Planets Forming Around Brown Dwarfs

Brown dwarfs are often surrounded by disks that exhibit many of the same features as disks around stars. These disks provide the material necessary for the formation of planets. Given the relatively small mass of the brown dwarf disks, the resulting planets are most likely to be terrestrial rather than gas giants. The process of accretion forms these planets, much like how planets form in other stellar systems. This is a testament to the similarity in the underlying physics of planetary formation across various stellar environments.

The study of planets around brown dwarfs not only expands our understanding of planetary science but also provides valuable insights into the diversity of planetary systems in the universe. Future research will likely uncover even more fascinating examples of planets orbiting these intriguing stellar objects.