Chong Li, Rouyu Li, Keping Qiu, Marko Krco, Di Li, Hongchi Wang, Xin Lyu, Yan Duan, Min Fang, Xuepeng Chen, Lile Wang, Haoran Feng, Shuinai Zhang, Miaomiao Zhang, Shaobo Zhang, Yue Cao, Yao Wang, Yan Gong, Fujun Du, Zhiwei Chen, Yang Su, Yuehui Ma, Yuchen Xing, Yinghui Zheng, Tianwei Zhang, Shu Niu, Chenrui Li, Jiawei Liu, Zhijun Zhang, Yulian Guo
Feedback from massive stars regulates the formation of next-generation stars and planets and thus shapes the evolution of galaxies, yet observational evidence capable of determining which mechanism dominates the feedback process has long been lacking. Here, we present a large-scale HI survey toward Orion A. With an unprecedented sensitivity and superior resolution, FAST (Five-hundred-meter Aperture Spherical radio Telescope) reveals a well-defined heart-shaped expanding HI bubble, enshrouding the well-known "Veil" bubble of ionized gas. The photoionization-driven and wind-driven gas expands at 10.9 and 13.8 kilometers per second, respectively, with a kinetic energy ratio of 1:2 assuming a spherical symmetry and a uniform HI-to-H2 ratio. This first direct comparison within a single bubble shows that radiation does not dominate the feedback process as predicted by classical theories; instead, stellar winds contribute a comparable share of the injected kinetic energy.