Drawing of a T-Tauri star with a circumstellar accretion disk

T Tauri stars are a class of variable stars named after their prototype - T Tauri. They are found near molecular clouds and identified by their optical variability and strong chromospheric lines. Image File history File links TTauriStarDrawing. ... Image File history File links TTauriStarDrawing. ... The Pleiades star cluster A star is a massive body of plasma in outer space that is currently producing or has produced energy through nuclear fusion. ... T Tauri is a variable star in the constellation Taurus. ... A Molecular cloud is a type of interstellar cloud whose density and size permits the formation of molecular hydrogen, H2. ... Most stars are of almost constant luminosity. ... The chromosphere (literally, color sphere) is a thin layer of the Suns atmosphere just above the photosphere, roughly 10,000 kilometers deep. ...

T Tauri stars are the youngest visible stars. Their surface temperatures are similar to those of main sequence stars of the same mass, but they are significantly more luminous because their radii are larger. Their central temperatures are too low for hydrogen burning. Instead, they are powered by gravitational energy released as the stars contract towards the main sequence, which they reach after about 100 million years. They typically rotate with a period between one and twelve days, compared to a month for the Sun, and are very active and variable. Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve where the majority of stars are located in this diagram. ... Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve where the majority of stars are located in this diagram. ...

There is evidence of large areas of starspot coverage, and they have intense and variable X-ray and radio emissions (approximately 1000 times that of the Sun). Many have extremely powerful stellar winds. 400 year sunspot history A sunspot is a region on the Suns surface (photosphere) that is marked by a lower temperature than its surroundings, and intense magnetic activity. ... In the NATO phonetic alphabet, X-ray represents the letter X. An X-ray picture (radiograph) taken by Röntgen An X-ray is a form of electromagnetic radiation with a wavelength approximately in the range of 5 pm to 10 nanometers (corresponding to frequencies in the range 30 PHz... A solar wind is a stream of particles (mostly high-energy protons ~ 500 keV) which are ejected from the upper atmosphere of a star (in the case of a star other than the Earths Sun, it may be called a stellar wind instead). ...

Their spectra show a higher lithium abundance than the Sun and other main sequence stars because lithium is destroyed at temperatures above 2,500,000 K. From a study of lithium abundances in 53 T Tauri stars, it has been found that lithium depletion varies strongly with size, suggesting that "lithium burning" by the P-P chain, during the last highly convective and unstable stages during the pre main sequence later phase of the Hayashi contraction may be one of the main sources of energy for T Tauri stars. Rapid rotation tends to improve mixing and slow the transport of lithium into deeper layers where it is destroyed. Stars generally slow their rotation rates as they age, through the transfer of angular momentum to the protoplanetary disc. This causes an increased rate of lithium loss with age. Lithium burning will also increase with higher temperatures and mass, and will last for at most a little over 100 Myr (megayears = 100,000,000 years). General Name, Symbol, Number lithium, Li, 3 Chemical series alkali metals Group, Period, Block 1, 2, s Appearance silvery white/gray Atomic mass 6. ... Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve where the majority of stars are located in this diagram. ...

The P-P chain for Lithium burning is as follows

• 
• (unstable)
• 

It will not occur in stars with a mass of less than 60 Jupiters. In this way, the rate of lithium depletion can be used to calculate the age of the star.

Roughly half of T Tauri stars have circumstellar disks, which in this case are called protoplanetary disc because they are probably the progenitors of planetary systems like the solar system. 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 Alfven 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. A protoplanetary disc (also protoplanetary disk, proplyd) is an accretion disc surrounding a T Tauri star. ... A protoplanetary disc (also protoplanetary disk, proplyd) is an accretion disc surrounding a T Tauri star. ... An artists concept of a protoplanetary disk. ... Artists impression of a binary star system consisting of a black hole, with an accretion disc around it, and a main sequence star. ... Current flowing through a wire produces a magnetic field (B, labeled M here) around the wire. ... The plasma in the solar wind meeting the heliopause For the British comic, see Solar Wind (comic). ... A cluster of double layers forming in an Alfvén wave, about a sixth of the distance from the left. ... Gyroscope. ... A protoplanetary disc (also protoplanetary disk, proplyd) is an accretion disc surrounding a T Tauri star. ... The solar system comprises the Earths Sun and the retinue of celestial objects gravitationally bound to it. ... Gyroscope. ... The Sun is the star at the center of Earths solar system. ... A protoplanetary disc (also protoplanetary disk, proplyd) is an accretion disc surrounding a T Tauri star. ... A planet (from the Greek πλανήτης, planetes or wanderers) is a body of considerable mass that orbits a star and that produces very little or no energy through nuclear fusion. ...

References

• Discussion of V471 Tauri observations and general T-Tauri properties]