T Tauri star - wikipedia T Tauri star This article is about the type of variable star. For the particular variable star called `` T Tauri '', see T Tauri. This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. ( January 2017 ) Drawing of a T Tauri star with a circumstellar accretion disc Star formation Object classes Interstellar medium Molecular cloud Bok globule Dark nebula Young stellar object Protostar T Tauri star Pre-main - sequence star Herbig Ae / Be star Herbig -- Haro object Theoretical concepts Accretion Initial mass function Jeans instability Kelvin -- Helmholtz mechanism Nebular hypothesis Planetary migration Star portal T Tauri stars ( TTS ) 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. T Tauri stars are pre-main - sequence stars in the process of contracting to the main sequence along the Hayashi track, a luminosity -- temperature relationship obeyed by infant stars of less than 3 solar masses ( M ) in the pre-main - sequence phase of stellar evolution. It ends when a star of 0.5 M develops a radiative zone, or when a larger star commences nuclear fusion on the main sequence. Contents 1 Characteristics 2 Types of T Tauri stars 3 Planets 4 See also 5 References Characteristics T Tauri stars are the youngest visible F, G, K, M spectral type stars ( < 2 M ). 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 fusion. Instead, they are powered by gravitational energy released as the stars contract, while moving 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. 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 ; some eject gas in high - velocity bipolar jets. Another source of brightness variability are clumps ( protoplanets and planetesimals ) in the disk surrounding T Tauri stars. The ejection of a bubble of hot gas from XZ Tauri, a binary system of T Tauri stars. The scale is much larger than that of the Solar System. 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 later pre -- main sequence 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 increase the transport of lithium into deeper layers where it is destroyed. T Tauri stars generally increase their rotation rates as they age, through contraction and spin - up, as they conserve angular momentum. 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 million years. The P-P chain for Lithium burning is as follows p + 6 3Li → 7 4Be 7 4Be + e − → 7 3Li + ν p + 7 3Li → 8 4Be ( unstable ) 8 4Be → 2 4 2He + energy It will not occur in stars with less than sixty times the mass of Jupiter ( M ). In this way, the rate of lithium depletion can be used to calculate the age of the star. 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. Protoplanetary discs in the Orion Nebula 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. AT Tauri stage for the 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. 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-type 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. Planets Planets around T Tauri stars include : HD 106906 b around an F - type star 1RXS J160929. 1 − 210524 around an K - type star Gliese 674 b around an M - type star V830 Tau b around an M - type star See also Orion variables P Cygni profile References Jump up ^ T Tauri Stars, Naked and Otherwise, Scott J. Wolk, 1996. Appenzeller, Immo ; Mundt, Reinhard ( 1989 ). `` T Tauri Stars ''. Astronomy and Astrophysics Review. 1 ( 3 -- 4 ) : 291 -- 334. Bibcode : 1989A&ARv... 1... 291A. doi : 10.1007 / BF00873081. Discussion of V471 Tauri observations and general T - Tauri properties, Frederick M. Walter, Stony Brook University, April 2004 An empirical criterion to classify T Tauri stars and substellar analogs using low - resolution optical spectroscopy, David Barrado y Navascues, 2003 Star Formation Accretion Molecular cloud Bok globule Young stellar object Protostar Pre-main - sequence star Herbig Ae / Be Orion T Tauri FU Orionis Herbig -- Haro object Hayashi track Henyey track Evolution Main sequence Red giant branch Horizontal branch Red clump Asymptotic giant branch Protoplanetary nebula Planetary nebula PG1159 star Dredge - up Instability strip Luminous blue variable Blue straggler Stellar population Supernova Supernova impostor Hypernova Hertzsprung -- Russell diagram Color -- color diagram Luminosity class Subdwarf Dwarf Blue Red White Yellow Brown Subgiant Giant Blue Red Bright giant Supergiant Blue Red Yellow Hypergiant Yellow Spectral classification WR Be OB Subdwarf O Subdwarf B Late - type Chemically peculiar Am Ap / Bp Barium Carbon CH CN Extreme helium Lambda Boötis Lead HgMn Technetium Shell Remnants White dwarf Helium planet Neutron star Radio - quiet Pulsar Binary X-ray Magnetar Stellar black hole X-ray binary Burster Theoretical stars Black dwarf Exotic Quark Strange Preon Planck Electroweak star Dark - matter star Dark - energy star Black star Gravastar Frozen star Q star Quasi-star Thorne -- Żytkow object Iron star Blitzar Nucleosynthesis Deuterium burning Lithium burning Proton -- proton chain CNO cycle Helium flash Triple - alpha process Alpha process Carbon burning Neon burning Oxygen burning Silicon burning S - process R - process Fusor Nova Symbiotic Remnant Luminous red nova Structure Core Convection zone Microturbulence Oscillations Radiation zone Atmosphere Photosphere Starspot Chromosphere Corona Stellar wind Bubble Bipolar outflow Accretion disk Asteroseismology Helioseismology Eddington luminosity Kelvin -- Helmholtz mechanism Properties Designation Dynamics Effective temperature Kinematics Magnetic field Absolute magnitude Mass Metallicity Rotation UBV color Variable star Mira variable Star systems Binary Contact Common envelope Eclipsing Multiple Star cluster Open cluster Globular cluster Super star cluster Planetary system Earth 's Solar System Earth - centric observation of Pole star Circumpolar star Constellation Asterism Magnitude Apparent Extinction Photographic Radial velocity Proper motion Parallax Photometric - standard star Lists Star names Arabic Chinese Extremes Most massive Highest temperature Largest volume Smallest volume Brightest Historical Most luminous Nearest Nearest bright Stars with exoplanets Brown dwarfs White dwarfs Milky Way novae Notable supernovae Supernova candidates Supernova remnants Planetary nebulae Timeline of stellar astronomy Related articles Substellar object Brown dwarf Sub-brown dwarf Planet Galactic year Galaxy Supercluster Guest star Gravity Intergalactic star Infrared dark cloud Starfield Category : Stars Star portal GND : 4186382 - 3 Retrieved from `` https://en.wikipedia.org/w/index.php?title=T_Tauri_star&oldid=814998380 '' Categories : Star types T Tauri stars Star formation Hidden categories : Articles needing additional references from January 2017 All articles needing additional references Wikipedia articles with GND identifiers Talk Contents About Wikipedia Afrikaans Asturianu Bosanski Català Čeština Deutsch Ελληνικά Español Euskara فارسی Français 한국어 Hrvatski Bahasa Indonesia Italiano עברית Lëtzebuergesch Lietuvių Nederlands 日本 語 Norsk Norsk nynorsk Polski Português Română Русский Slovenčina Српски / srpski Srpskohrvatski / српскохрватски Suomi Svenska ไทย Türkçe Українська 中文 Edit links This page was last edited on 12 December 2017, at 03 : 44. 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Question: where are t-tauri stars found on the hr diagram
Answer: near molecular clouds