2026-03-11 ワシントン大学(UW)
Lead author Andy Tzanidakis’ rendering of the planetary collision he suspects occurred around star Gaia20ehk in 2021. Photo: Andy Tzanidakis
＜関連情報＞
- https://www.washington.edu/news/2026/03/11/uw-astronomers-spot-planet-collision-evidence/
- https://iopscience.iop.org/article/10.3847/2041-8213/ae3ddc
Gaia-GIC-1：進化する壊滅的な微惑星衝突候補 Gaia-GIC-1: An Evolving Catastrophic Planetesimal Collision Candidate
Anastasios Tzanidakis and James R. A. Davenport
The Astrophysical Journal Letters Published: 2026 March 11
DOI:10.3847/2041-8213/ae3ddc
Abstract
We report the discovery of the optical dipper and low-luminosity infrared stellar transient Gaia20ehk (hereafter, Gaia-GIC-1), which is currently undergoing high-amplitude variability due to transiting dusty material. In this work, we identify Gaia-GIC-1 as a likely young F-type star based on the spectral energy distribution before the onset of the high-amplitude optical variability. We detect a significant periodic modulation of 380.5 days in Gaia G band before the onset of the infrared brightening, consistent with a ∼1.1 au orbit assuming circular orbits and a 1.3 M⊙ star. The system has remained in an infrared-bright state for >4 yr since the last near-infrared detection, confirmed by recent SPHEREx observations, while continuing to undergo large-amplitude irregular optical dimming. We measure the dust temperature from the freshly generated debris to be ∼900 K based on available Wide-field Infrared Survey Explorer photometry, and the dust clump size to have a minimum cross-sectional area of 0.13 au2, and the dust mass 4 × 1020 kg. Currently, optical follow-up spectroscopy has not revealed any prominent features in the system, likely due to its highly variable nature. We hypothesize that Gaia-GIC-1 represents debris recently formed in a planetary collision, which produced a clumpy dust cloud on a bound orbit, producing the observed dimming events. The ongoing collisional activity in this system presents a unique opportunity for understanding terrestrial planet formation.
