T Tauri stars

T Tauri stars

(tor -ÿ, -ee) Variable stars of spectral type G or later whose spectra are dominated by strong emission lines, usually attributed to chromospheric activity and stellar winds in these stars. They are invariably embedded in dense patches of gas and dust that may require observations in the infrared: the dust absorbs the visible light of the star and reradiates it at longer wavelengths. The prototype is T Tauri. T Tauri stars are usually found together in groups (T associations) and are the youngest optically observable stages in the life of a star of about the Sun's mass; more massive counterparts are observed as Ae and Be stars. They are frequently associated with Herbig–Haro objects.

There is much evidence that T Tauri stars are young objects, for instance they have a high abundance of lithium, an element destroyed fairly early in a star's life, and they are surrounded by gas and dust. They are thought to be young protostars that have only recently contracted out of the interstellar medium (see star formation). Lying above the main sequence in the Hertzsprung–Russell diagram, they are still contracting and losing mass (see T Tauri wind). Their spectral lines reveal that some are extremely rapid rotators, throwing off material at speeds of up to 300 km s–1. The irregular light variations are believed to arise partly from activity in the chromospheres of these young stars, and partly by the obscuring effect of the patchy dust in the cocoon as it moves in front of the star.

The original class of T Tauri stars, characterized by strong hydrogen emission lines, are often known as classical T Tauri stars (CTTS) to distinguish them from naked or weak-line T Tauri stars (WTTS); the latter have very weak hydrogen emission lines, often discovered in X-rays, and are much less active than the classical type. WTTS may represent a later phase of pre-main-sequence evolution than CTTS or a different evolutionary channel, as may be suggested by the apparently higher frequency of binaries among WTTS than among CTTS and main-sequence stars. See also FU Orionis; YY Orionis stars.

References in periodicals archive ?
Our goal is to give closure to the question: how do x-rays impact disk evolution and early planet formationthis project will go beyond the state-of-the-art in two directions: via the laboratory simulation of the x-ray spectrum of t tauri stars, and by pioneering the use of heterogeneous analogs to protoplanetary dust.
As part of the DARTTS-S or Discs Around T Tauri Stars with SPHERE survey, it allowed the team to suppress light from the stars and lay more focus on the areas surrounding them - more specifically the discs made from gas, dust, and planetesimals, which are the building blocks of planetary bodies.
It has since been identified as the prototypical cometary nebula, a class of fan-shaped reflection nebulae that are often associated with T Tauri stars (very young, variable, low-mass stars often in binary systems; some have circumstellar disks and are likely progenitors of planetary systems).
Classical T Tauri stars are often surrounded by dust and gas.
T Tauri stars show outbursts of this kind, and so do FU Orionis stars, but FU Orionis spectra show absorption of light by calcium, whereas Object 50 shows emission by calcium.
Newborn Stars "One of the most exciting and controversial papers was 'On the Nature and Origin of the T Tauri Stars,' by G.
Unlike the Orion Nebula, it isn't forming massive stars but contains hosts of low-mass protostars in the process of formation: so-called T Tauri stars. Many are visible through amateur telescopes, but only deep imaging can detect the surrounding dusty disks and the jets that the stars produce as matter from the disks falls onto them.
Most infant stars having roughly the Sun's mass (T Tauri stars) appear to blow away their dusty disks in less than 10 million years and perhaps just 3 million years.
The variations we see in T Tauri stars are not evolutionary changes as such, only instabilities in the disk.
Its spectrum shows anomalously intense blue emission lines of neutral iron at 4046 and 4132 angstroms, as well as other unusual features shared by many young, premain-sequence variables - which have become known as the T Tauri stars.
As an example of recent developments, Italian astronomer Antonio Magazzu and colleagues from Spain and Ukraine used the 2.5-meter Isaac Newton Telescope in the Canary Islands to take high-dispersion spectra of 36 T Tauri stars. These stars are so young that they presumably haven't had a chance to destroy the lithium with which they formed.
Much slower, broader bipolar outflows are found in many well-studied protostars, particularly the famous T Tauri stars. Occasionally these outflows surround more tightly collimated jets of ionized gas (and their associated Herbig-Haro objects) that can move with speeds of several hundred kilometers per second.