Window of soft X-ray polarization re-opens with PolarLight

PolarLight is a dedicated astronomical X-ray polarimeter based on the gas pixel detector and was launched into a low-Earth orbit in October 2018 onboard a CubeSat. With the first-year data, polarization in the soft X-ray band from the Crab nebula has been detected, indicating that this window in astronomy re-opens after more than 40 years since the experiment on OSO-8 in the 1970s. A time variation in polarization, possibly associated with a glitch of the Crab pulsar, is revealed at a significance of 3σ, suggesting that the magnetosphere of the pulsar may have altered due to the glitch.