Atmospheric chemistry and isotope ratios in β Pictoris group reveal star-like formation for planetary-mass companion

Star system: Beta Pictoris | Distance from the Sun: 64 light years

The β Pictoris young moving group contains a variety of substellar objects, including gas giants and brown dwarfs. Scientists studied the atmospheric chemistry and isotope ratios of three members: the planetary-mass companion 2MASS J0249-0557 c and two benchmark brown dwarfs. Using high-resolution spectroscopy, they measured the carbon-to-oxygen ratio, metallicity, and the ratio of carbon isotopes in their atmospheres.

2MASS J0249-0557 c, with a mass near the boundary between planets and brown dwarfs, has a C/O ratio of 0.57, a metallicity slightly above solar, and a ^12CO/^13CO ratio of about 95. The two brown dwarfs show similar atmospheric compositions. The consistency in chemistry and isotope ratios among these objects, along with the wide separation of 2MASS J0249-0557 c from its host, suggests that it formed through gravitational collapse like a star, rather than by core accretion like most planets.

These results provide a baseline for comparing other exoplanets in the β Pictoris group and help distinguish between different formation mechanisms for planetary-mass objects.

Key findings
- 2MASS J0249-0557 c has a C/O ratio of 0.57 and metallicity slightly above solar
- The ^12CO/^13CO ratio is about 95
- Atmospheric compositions are consistent among three substellar objects
- Results support star-like formation by gravitational collapse
- Provides a baseline for comparing other exoplanets in the group

Scientific study

Chemistry and Isotope Ratios of Substellar Atmospheres in the β Pictoris Young Moving Group (external link)