Analysis of dust rings in the protoplanetary disk around LkCa 15

Star system: LkCa 15 | Distance from the Sun: 513 light years

Protoplanetary disks are vast, swirling clouds of gas and dust surrounding young stars that eventually coalesce to form planets. A new method has been developed to analyze the physical properties of these disks by examining how their dust rings appear when viewed at an angle. By studying these shapes, researchers can determine the intrinsic width, thickness, and light-blocking capacity, known as optical depth, of the dust material within the disk surrounding the star LkCa 15.

Researchers applied this technique to archival images from the Atacama Large Millimeter/submillimeter Array (ALMA) telescope, observing the LkCa 15 disk across different wavelengths. They found that as the wavelength of light increases, the ring appears to become thinner and more transparent. This indicates that the disk contains a mixture of different dust grain sizes, rather than uniform particles throughout the structure.

By modeling the data, the study revealed that the ring is composed of a massive population of small dust grains, less than 20 microns in size, which are spread widely across the ring. Intermixed with these are smaller, denser groups of larger grains, exceeding 200 microns. This discovery challenges current theories of how dust particles clump together, suggesting that small grains remain more abundant than previously expected in such environments.

Key findings
- The optical depth of the LkCa 15 ring decreases significantly as the wavelength of light increases.
- Both the physical width and height of the dust ring shrink when viewed at longer wavelengths.
- The disk contains a massive, broadly distributed population of small dust grains totaling approximately 100 times the mass of Earth.
- A separate, more concentrated population of larger dust grains exists within the ring structure.
- The observed high abundance of small dust grains provides an explanation for the fluffy appearance of the disk.

Scientific study

Geometry of dust rings in protoplanetary disks: the case of LkCa 15 (external link)