A Star Winks: Dust from a Planetary Collision express
In a constellation where new stars are born, one of them behaves like a faulty lightbulb: sometimes shining steadily, sometimes dimming by a factor of several. Astronomers have been monitoring the star Gaia-GIC-1 for several years and now understand that its blinking is the shadow of a huge dust cloud that periodically passes in front of it. The dust is not just cosmic debris but fresh fragments: it seems that two planets recently collided there.
Every 380 days, the cloud completes an orbit and blocks the star again. Scientists have measured that there is a lot of dust — by mass, equivalent to a small asteroid. And it doesn't disperse but holds together, like a clump of mud thrown into a pond. This means the debris hasn't had time to spread out and continues to collide with itself, generating new particles.
Such observations are a rare stroke of luck. Usually we see fully formed planets, but here we witness the very process of their assembly. Perhaps, in a few million years, a new planet will form from this dust, like a pie from dough. And then the star will stop winking.
Original abstract
as written by the authors arXiv:2603.10952
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 $$\sim$$1.1 AU orbit assuming circular orbits and a 1.3 M$$_{\odot}$$ star. The system has remained in an infrared bright state for $$>$$4 years 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 $$\sim$$900 Kelvin based on available WISE photometry, and the dust clump size to have a minimum cross-sectional area of 0.13 AU$$^{2}$$, and the dust mass $$4\times 10^{20}$$ 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.
The dust cloud is so dense that at times it blocks more than half of the star's light — as if someone covered a flashlight with their palm.