Disk surrounding the binary star DX Chamaeleontis may orbit in reverse

Star system: DX Chamaeleontis A | Distance from the Sun: 348 light years

DX Chamaeleontis (HD 104237) is a binary star system surrounded by a compact, asymmetric ring of dust and gas at a radius of 0.43 astronomical units. This ring lies just outside the binary’s orbit, much closer than expected for a typical circumbinary disk. 

Normally, the strong gravity of the binary would clear out the inner region, creating a large gap between the stars and the disk. Previous simulations, assuming the disk orbits in the same direction as the binary, found almost no material close to the stars.

However, new study shows that if the disk orbits in the opposite direction — a retrograde orbit — the inner edge can be much closer, matching the observed ring. The retrograde disk forms one or two arcs, just as seen in observations. This suggests that the circumbinary disk in DX Chamaeleontis may be orbiting in reverse relative to the binary stars. If confirmed, this finding would have major implications for our understanding of how stars and planets form in binary systems, as retrograde disks behave very differently from prograde ones.

Key findings
- DX Chamaeleontis circumbinary disk is unusually close to the binary stars, forming a compact arc
- Simulations show that a retrograde disk can exist much closer to the binary than a prograde disk
- The observed arc structure matches predictions for a retrograde disk
- This may be the first evidence for a retrograde circumbinary disk in a young stellar system
- The result could change our understanding of star and planet formation in binary systems

Scientific study

The Arc in the DX Cha Circumbinary System: Evidence For a Retrograde Circumbinary Disk (external link)