Ionized by energetic starlight, a hydrogen atom emits the characteristic red H-alpha light as its single electron is recaptured and transitions to lower energy states.

氢原子被高能的恒星光离子化之后，在它的单个电子重新被捕获并跃迁到低能级上时会放出典型的红色h - alpha光。

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One of LRO's instruments, the Lyman Alpha Mapping Project (Lamp), detected enhanced concentrations of mercury and atomic hydrogen in the cloud from the demise of the twin spacecraft.

BBC: Nasa reveals new information about moon probes crash sites

Scientists working on the Alpha project at Cern are trying to find out by isolating and studying particles of anti-hydrogen.

BBC: The problem with anti-matter