Multi-Epoch Analysis of HD 135344B Disk Supports Spiral-Driving Protoplanet Hypothesis
Astronomers analyzing a decade of multi-instrument observations of the protoplanetary disk around HD 135344B have found that a spiral structure, a dust filament, and a morphological 'twist' all move together at a rate consistent with a single planet orbiting at roughly 69 astronomical units from the star. The study used advanced post-processing techniques on data from VLT/NACO, VLT/SPHERE, VLT/ERIS, and JWST/NIRCam to track the disk's spiral arms over a 10-year baseline. The findings strengthen the case that multiple observed disk features — including a previously detected sub-millimeter gap and dust filament — are all caused by one as-yet-undetected protoplanet, while also debunking a recently claimed direct detection of that planet as an imaging artifact.
A new peer-reviewed study accepted by Astronomy & Astrophysics presents multi-epoch scattered-light analysis of the protoplanetary disk surrounding HD 135344B (also known as SAO 206462), a young star known for its striking spiral disk structure. Using high-fidelity post-processing algorithms including IPCA — designed to reduce biases introduced by angular differential imaging on extended sources — the team measured an average spiral orbital motion of 0.81 ± 0.05 degrees per year across multiple wavelength bands, consistent with prior literature values of approximately 0.85 ± 0.05 degrees per year. Crucially, the study confirms that a morphological 'twist' embedded within one of the spirals is co-moving with the spiral itself, and that its position angle aligns with a dust filament previously detected in ALMA sub-millimeter observations. The authors attribute the twist's slightly smaller angular separation from the star compared to the filament to a wavelength-dependent shift in spiral trace position — a puzzling trend they note remains unexplained. Taken together, the consistent orbital motion of the spirals, the twist, the gap, and the dust filament over a 10-year baseline is interpreted as strong circumstantial evidence that all these features are driven by a single hypothetical protoplanet orbiting at 69 ± 4 au. The study also finds that a recently published candidate direct detection of this protoplanet is most likely a post-processing artifact rather than a genuine point source.
What's missing
The authors acknowledge the wavelength-dependence of spiral trace angular separation as an unexplained phenomenon. The planet remains undetected directly, so all conclusions rest on indirect dynamical evidence.
What different sources said
- arXiv astro-phCenter
Ultraviolet Imaging of SR 12 c with HST/WFC3: Accretion and Variability of a Giant Planet at the End Stages of Growth
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