Cosmic Disks Flicker Like Candles express
Around young stars, flat clouds of gas and dust swirl — the building material for future planets. Starlight reflects off these clouds, and astronomers see them as faint disks. But sometimes bright spots or dark bands appear in such disks. Fresh observations with the Subaru Telescope show these patterns can change within a matter of months.
The researchers examined nine stars similar to our Sun but younger. For three of them — MWC 480, HD 163296, and HD 143006—they managed to resolve the disks using a new technique that filters out the direct starlight. In the first two disks, brightness varied. In one case, a dark band shifted over a year; in another, a bright spot crept along the ring over fifteen months.
So the spots are not riding along with the gas. More likely, the star illuminates the disk unevenly: like a flashlight sweeping its beam across a wall. A shadow or glint races across the disk while the disk itself stays put. That said, exactly what creates this play of light remains unclear.
Six more stars in the sample showed no disks at all. Their disks are probably tilted so that they hide in their own shadow. But the astronomers did measure the overall light signature of these hidden systems. Each such measurement is a step toward understanding how planets assemble from dust.
Original abstract
as written by the authors arXiv:2602.20346
Using the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument, we present near-infrared K-band polarimetric imaging of nine Herbig stars selected from a volume-limited sample within 200 pc. We detect the disks around MWC 480, HD 163296, and HD 143006 for the first time with SCExAO, and compare these observations with previous VLT/SPHERE datasets to identify surface-brightness variability. In MWC 480, we resolve two azimuthal brightness dips near the disk minor axis and find evidence that one of them shifted between 2021 and 2022. In HD 163296, we identify an apparent linear azimuthal motion of a localized peak in polarized intensity along the outer ring over a 15-month baseline. The rapid motion of these features relative to the local Keplerian velocity suggests that the observed variability is driven by changing illumination rather than physical material motion. Due to uncertainties in the underlying scattering background, however, we cannot determine the precise physical origin of the variability. No significant disk variability is detected in HD 143006 over a 10-month baseline. We also report the first detection of a protoplanetary disk using the fast-PDI mode on SCExAO, illustrating both the promise and current limitations of this observing mode. Finally, we report non-detections toward HD 144432, HD 56895, PDS 76, HIP 80425, HD 148352, and HIP 81474. All non-detections with Meeus classifications belong to Group II systems and are likely self-shadowed. For these six systems, we measure the system-integrated polarization fraction and angle of linear polarization, providing quantitative constraints on their unresolved circumstellar environments.
Disks around young stars are so faint that their light is millions of times weaker than the star's own light. To see them, telescopes use special masks that block the star, like a hand shielding the Sun.
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