Inclined eccentric planet model explains moving dust clumps around the star AU Microscopii

Star system: AU Microscopii | Distance from the Sun: 31.7 light years

The red dwarf star AU Microscopii is surrounded by a complex debris disk—a ring of dust and rocky debris—that features unusual clumps of dust moving at high speeds. These features, visible only when scattering light from the star, consist of tiny grains about 0.2 micrometers in size. New simulations suggest that the observed motion of these dust clumps may be caused by the gravitational influence of a yet-to-be-confirmed planet interacting with the surrounding disk material.

Researchers modeled how a planet with an inclined, eccentric orbit could stir up the disk. By exerting a periodic gravitational impulse on the disk, the planet could push dust grains above the mid-plane of the system. Once these grains reach a certain height, the star's powerful stellar wind—a flow of charged particles—accelerates them outward, creating the observed clumpy structures.

The simulation successfully reproduces the observed disk features by incorporating a hypothetical planet with a mass twice that of Jupiter. This planet would have an eccentric orbit—meaning it is oval rather than circular—inclined at an angle of 30 degrees relative to the disk. When the ratio of stellar wind force to gravity is set to 1.8, the simulated dust clumps move at velocities that match the features documented in previous observations of the star.

Key findings
- Simulations explain the movement of dust clumps around the red dwarf AU Microscopii.
- An inclined, eccentric planet with two Jupiter masses could generate these periodic dust ejections.
- Stellar wind accelerates dust grains outward once they are lifted above the disk's mid-plane.
- Model results match observed disk features with a planetary eccentricity of 0.37 and an inclination of 30 degrees.

Scientific study

An Inclined, Eccentric Planet and an Inner Debris Disk Could Reproduce AU Mic Structure (external link)