T Tauri Stars
With ground-based optical follow-up observations of unidentified ROSAT All-Sky Survey sources, several hundred new T Tauri stars have been identified based on Halpha emission and Lithium absorption. T Tauri stars are young (at most a few million years old) bright stars still partially wrapped in the cloud of dust and gas where they were created.
Surprisingly, new T Tauri stars have been found even outside clouds, i.e. outside regions of on-going star formation. Such off-cloud T Tauri stars either have been ejected from their birth places in the clouds or they formed in small cloudlets which have dispersed since then.
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