An Etymological Dictionary of Astronomy and Astrophysics

A → stellar association containing many → T Tauri stars. Examples include the Taurus-Auriga T association, the nearby → TW Hydrae association, and Vela T1 and T2.

See also: T, letter of alphabet; → association.

A → stellar association containing many → T Tauri stars. Examples include the Taurus-Auriga T association, the nearby → TW Hydrae association, and Vela T1 and T2.

See also: T, letter of alphabet; → association.

A type of → brown dwarf with an → effective temperature between about 1200 K and 500 K, i.e. colder than the preceding type → L dwarf. The spectra of T dwarfs are characterized by the presence of → methane (CH₄) bands in the → near infrared.
The presence of these bands, broad H₂O features, and H₂ collision-induced absorption radically alter the spectral energy distributions of T dwarfs compared to a black body at the same temperature. Hence near-infrared colors become increasingly blue (J - K ~ 0) as compared to L dwarfs. The first T dwarf, called
→ Gl 229B, was discovered by Nakajima et al. (1995, Nature 378, 463). The spectral classification scheme
(subtypes T0 to T9) currently
used was defined by Burgasser et al. (2002, ApJ 564, 421).

See also: For the reasoning behind the choice of the letter T, see Kirkpatrick et al. 1993, ApJ 406, 701; → dwarf.

A type of → brown dwarf with an → effective temperature between about 1200 K and 500 K, i.e. colder than the preceding type → L dwarf. The spectra of T dwarfs are characterized by the presence of → methane (CH₄) bands in the → near infrared.
The presence of these bands, broad H₂O features, and H₂ collision-induced absorption radically alter the spectral energy distributions of T dwarfs compared to a black body at the same temperature. Hence near-infrared colors become increasingly blue (J - K ~ 0) as compared to L dwarfs. The first T dwarf, called
→ Gl 229B, was discovered by Nakajima et al. (1995, Nature 378, 463). The spectral classification scheme
(subtypes T0 to T9) currently
used was defined by Burgasser et al. (2002, ApJ 564, 421).

See also: For the reasoning behind the choice of the letter T, see Kirkpatrick et al. 1993, ApJ 406, 701; → dwarf.

The most famous young stellar object, the prototype of → T Tauri stars which is located in the Taurus-Auriga star forming region at a distance of about 140 pc. T Tauri is about 2.4 solar masses and about 7 million years old. Complex structures of shock heated gas indicative of outflows surround the star, both on sub-arcsecond and larger scales. The → accretion rate is estimated to be (3-6) x 10^-8 solar masses per year. T Tauri has a companion (about 0.7 arcseconds apart) which is invisible in the optical and has been observed to be strongly variable in infrared. It is an intermediate mass
young star (2.5 solar masses) surrounded by a → circumstellar disk. This star is itself a → close binary, the component being a low mass star (0.6 solar masses) also surrounded by circumstellar material.

See also: T, letter of alphabet; Tauri genitive of → Taurus.

The most famous young stellar object, the prototype of → T Tauri stars which is located in the Taurus-Auriga star forming region at a distance of about 140 pc. T Tauri is about 2.4 solar masses and about 7 million years old. Complex structures of shock heated gas indicative of outflows surround the star, both on sub-arcsecond and larger scales. The → accretion rate is estimated to be (3-6) x 10^-8 solar masses per year. T Tauri has a companion (about 0.7 arcseconds apart) which is invisible in the optical and has been observed to be strongly variable in infrared. It is an intermediate mass
young star (2.5 solar masses) surrounded by a → circumstellar disk. This star is itself a → close binary, the component being a low mass star (0.6 solar masses) also surrounded by circumstellar material.

See also: T, letter of alphabet; Tauri genitive of → Taurus.

A member of a class of young stellar objects of roughly 1 solar mass showing strong → infrared excess emission attributed to → circumstellar disks and found within or close to molecular clouds. T Tauri stars are → protostars in the final stages of formation to become a stable → main sequence star. The nuclear reactions in their core have not yet stabilised and the stars are known for the variability of their brightness. See also → classical T Tauri star, → weak-line T Tauri star.

See also: → T Tauri; → star.

A member of a class of young stellar objects of roughly 1 solar mass showing strong → infrared excess emission attributed to → circumstellar disks and found within or close to molecular clouds. T Tauri stars are → protostars in the final stages of formation to become a stable → main sequence star. The nuclear reactions in their core have not yet stabilised and the stars are known for the variability of their brightness. See also → classical T Tauri star, → weak-line T Tauri star.

See also: → T Tauri; → star.

The symmetry of physical laws under a time reversal transformation.

See also: T for → time; → symmetry.

The symmetry of physical laws under a time reversal transformation.

See also: T for → time; → symmetry.