T Tauri
Encyclopedia
T Tauri is a variable star
in the constellation
Taurus
, the prototype of the T Tauri star
s. It was discovered in October 1852 by John Russell Hind
. T Tauri appears from Earth amongst the Hyades
cluster, not far from ε Tauri
; but it is actually 420 light years behind it and was not formed with the rest of them.
Like all T Tauri stars, it is very young, being only a million years old. Its distance from Earth
is about 460 light years, and its apparent magnitude
varies unpredictably from about 9.3 to 14.
The T Tauri system consists of at least three stars, only one of which is visible at optical wavelengths; the other two shine in the infrared and one of them also emits radio waves. Through VLA
radio observations, it was found that the young star (the "T Tauri star" itself) dramatically changed its orbit after a close encounter with one of its companions and may have been ejected from the system.
Physically nearby is NGC 1555
, a reflection nebula
known as Hind's Nebula or Hind's Variable Nebula. It is illuminated by T Tauri, and thus also varies in brightness. The nebula NGC 1554
was likewise associated with T Tauri and was observed in 1868 by Otto Wilhelm von Struve
, but soon disappeared or perhaps never existed, and is known as "Struve's Lost Nebula".
A Herbig-Haro object
also appears to be associated with Hind's nebula, or perhaps with the T Tauri system itself.
The T Tauri wind
, so named because this young star is currently in this stage, is a phase of stellar development between the accretion of material from the slowing rotating material of a solar nebula and the ignition of the hydrogen that has agglomerated into the protostar
. A protostar is the denser parts of a cloud core, typically with a mass around 104 solar masses in the form of gas and dust, that collapses under its own weight/gravity, and continues to attract matter.
The protostar, at first, only has about 1% of its final mass. But the envelope of the star continues to grow as infalling material is accreted. After a few million years, thermonuclear fusion begins in its core, then a strong stellar wind is produced which stops the infall of new mass. The protostar is now considered a young star since its mass is fixed, and its future evolution is now set.
Variable star
A star is classified as variable if its apparent magnitude as seen from Earth changes over time, whether the changes are due to variations in the star's actual luminosity, or to variations in the amount of the star's light that is blocked from reaching Earth...
in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
Taurus
Taurus (constellation)
Taurus is one of the constellations of the zodiac. Its name is a Latin word meaning 'bull', and its astrological symbol is a stylized bull's head:...
, the prototype of the T Tauri star
T Tauri star
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.-Characteristics:...
s. It was discovered in October 1852 by John Russell Hind
John Russell Hind
John Russell Hind FRS was an English astronomer.- Life and work :John Russell Hind was born in 1823 in Nottingham, the son of lace manufacturer John Hind, and was educated at Nottingham High School...
. T Tauri appears from Earth amongst the Hyades
Hyades (star cluster)
The Hyades is the nearest open cluster to the Solar System and one of the best-studied of all star clusters. The Hipparcos satellite, the Hubble Space Telescope, and infrared color-magnitude diagram fitting have been used to establish a distance to the cluster's center of ~153 ly...
cluster, not far from ε Tauri
Epsilon Tauri
Epsilon Tauri is an orange giant star, spectral type of K0 III, located approximately 147 light-years away from the Sun in the constellation of Taurus. It is a member of the Hyades open cluster...
; but it is actually 420 light years behind it and was not formed with the rest of them.
Like all T Tauri stars, it is very young, being only a million years old. Its distance from Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
is about 460 light years, and its apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
varies unpredictably from about 9.3 to 14.
The T Tauri system consists of at least three stars, only one of which is visible at optical wavelengths; the other two shine in the infrared and one of them also emits radio waves. Through VLA
Very Large Array
The Very Large Array is a radio astronomy observatory located on the Plains of San Agustin, between the towns of Magdalena and Datil, some fifty miles west of Socorro, New Mexico, USA...
radio observations, it was found that the young star (the "T Tauri star" itself) dramatically changed its orbit after a close encounter with one of its companions and may have been ejected from the system.
Physically nearby is NGC 1555
NGC 1555
NGC 1555, sometimes known as Hind's Variable Nebula, is a variable nebula, illuminated by the star T Tauri, located in the constellation Taurus. It is also in the second Sharpless catalog as 238. It is a Herbig–Haro object. -External links:*...
, a reflection nebula
Reflection nebula
In Astronomy, reflection nebulae are clouds of dust which are simply reflecting the light of a nearby star or stars. The energy from the nearby star, or stars, is insufficient to ionize the gas of the nebula to create an emission nebula, but is enough to give sufficient scattering to make the dust...
known as Hind's Nebula or Hind's Variable Nebula. It is illuminated by T Tauri, and thus also varies in brightness. The nebula NGC 1554
NGC 1554
NGC 1554, Struve's Lost Nebula, is a list entry in the New General Catalogue of Nebulae compiled by John L. E. Dreyer, which was discovered by the German-Russian astronomer Otto Wilhelm von Struve and confirmed by Heinrich Louis d'Arrest...
was likewise associated with T Tauri and was observed in 1868 by Otto Wilhelm von Struve
Otto Wilhelm von Struve
Otto Wilhelm von Struve was a Russian astronomer. In Russian, his name is normally given as Otto Vasil'evich Struve...
, but soon disappeared or perhaps never existed, and is known as "Struve's Lost Nebula".
A Herbig-Haro object
Herbig-Haro object
Herbig–Haro objects are small patches of nebulosity associated with newly born stars, and are formed when gas ejected by young stars collides with clouds of gas and dust nearby at speeds of several hundred kilometres per second...
also appears to be associated with Hind's nebula, or perhaps with the T Tauri system itself.
The T Tauri wind
T Tauri wind
The T Tauri wind — so named because of the young star currently in this stage—is a phenomenon indicative of the phase of stellar development between the accretion of material from the slowing rotating material of a solar nebula and the ignition of the hydrogen that has agglomerated into...
, so named because this young star is currently in this stage, is a phase of stellar development between the accretion of material from the slowing rotating material of a solar nebula and the ignition of the hydrogen that has agglomerated into the protostar
Protostar
A protostar is a large mass that forms by contraction out of the gas of a giant molecular cloud in the interstellar medium. The protostellar phase is an early stage in the process of star formation. For a one solar-mass star it lasts about 100,000 years...
. A protostar is the denser parts of a cloud core, typically with a mass around 104 solar masses in the form of gas and dust, that collapses under its own weight/gravity, and continues to attract matter.
The protostar, at first, only has about 1% of its final mass. But the envelope of the star continues to grow as infalling material is accreted. After a few million years, thermonuclear fusion begins in its core, then a strong stellar wind is produced which stops the infall of new mass. The protostar is now considered a young star since its mass is fixed, and its future evolution is now set.
External links
- AAVSO Variable Star of the Month Profile of T Tauri
- http://www.kencroswell.com/TTauri.html
- http://www.spaceref.com/news/viewpr.html?pid=10340
- http://www.daviddarling.info/encyclopedia/T/T_Tauri.html
- Simbad