Variable of the type T Tauri

The variable of type T Tauri are variable stars, named according to the prototype star T Tauri. They are always located near the molecular clouds and characterized by abrupt and unforeseeable variations of their Magnitude connect.

The stars T Tauri are among young people that it is possible to see, old of 10 million years to the maximum, and with a mass lower than 3 solar masses. They are in fact in an intermediate phase between the stage of Protostar and that of star of low mass belonging to the principal Séquence, such as the Sun. Their temperature of surface is similar to that of of the same stars Masse of the principal sequence, but they are much more luminous because of their ray definitely larger. The temperature in the center of star is too low to start the nuclear process of Fusion of the Hydrogène, it thus draw their energy only from the gravitational energy released whereas the star contracts, for finally reaching the principal sequence after approximately 100 million years.

This type of star is often surrounded by a Disque of accretion, accumulated during the formation process of star. The variations of luminosity of star can be due to instabilities inside the accretion disc, to violent puffs of activity in the atmosphere of star, or to the cloud of surrounding molecular gas which can mask the glare of star while interposing between it and the observer.

These stars generally rotate into 1 to 12 days, the Sun having by comparison one period of one month rotation. There seems to also be evidence of the existence of stellar spots on the surface (similar to the sunspots), and these stars emit in an intense way and very variable in the fields of the waves radio and the x-rays (roughly 1000 times more than the Sun). The stellar wind produces by these stars is him also very powerful.

The spectrum of the stars T Tauri shows that it are richer in Lithium than stars of the principal sequence such as the Sun, which is characteristic of their youth, lithium being destroyed when the temperature exceeds 2  500  000 K.

There exist two principal types in the class of the variables T Tauri, differentiated by the characteristics from their electromagnetic spectra: T Tauri traditional , which have an accretion disc, and thus of the emission lines broad, and T Tauri with fine lines , whose accretion disc very thin and even non-existent, is characterized by fine and well differentiated spectral lines. The stars of this second type are very interesting for the astronomers, because they make it possible to observe and study the first stage of the formation of stars, without “pollution” by other matters surrounding.

The stars T Tauri closest to the Solar system are located in the molecular clouds of the Constellation of the Taureau (to which belonged the star T Tauri itself), and in that of the constellation of Ophiuchus, both located at approximately 460 light-years.

objects Herbig-Haro are often associated with the variables T Tauri.

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