Types of T Tauri Stars
There exist several types of TTSs:
- Classical T Tauri star (CTTS)
- Weak-line T Tauri star (WTTS)
- Naked T Tauri star (NTTS), which is a subset of WTTS.
Roughly half of T Tauri stars have circumstellar disks, which in this case are called protoplanetary discs because they are probably the progenitors of planetary systems like the solar system. Circumstellar discs are estimated to dissipate on timescales of up to 10 million years. Most T Tauri stars are in binary star systems. In various stages of their life, they are called Young Stellar Objects (YSOs). It is thought that the active magnetic fields and strong solar wind of Alfvén waves of T Tauri stars are one means by which angular momentum gets transferred from the star to the protoplanetary disc. A hypothesised T Tauri stage for our Solar System would be one means by which the angular momentum of the contracting Sun was transferred to the protoplanetary disc and hence, eventually to the planets, resulting in the theory that before our own Sun matured, it was once a T Tauri star.
Analogs of T Tauri stars in the higher mass range (2–8 solar masses)—A and B spectral type pre–main sequence stars, are called Herbig Ae/Be stars. More massive (>8 Solar mass) stars in pre–main sequence stage are not observed, because they evolve very quickly: when they become visible (i.e. disperses surrounding circumstellar gas and dust cloud), the hydrogen in the center is already burning and they are main sequence objects.
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