119 Tauri (also known as CE Tauri) is a

red supergiant Red supergiants (RSGs) are stars with a supergiant luminosity class ( Yerkes class I) of spectral type K or M. They are the largest stars in the universe in terms of volume, although they are not the most massive or luminous. Betelgeuse and Anta ...

star in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Taurus Taurus is Latin for 'bull' and may refer to: * Taurus (astrology), the astrological sign * Taurus (constellation), one of the constellations of the zodiac * Taurus (mythology), one of two Greek mythological characters named Taurus * ''Bos taurus ...

. It is a

semiregular variable In astronomy, a semiregular variable star, a type of variable star, is a giant or supergiant of intermediate and late (cooler) spectral type showing considerable periodicity in its light changes, accompanied or sometimes interrupted by various irre ...

and its angular diameter has been measured at about . It is a similar star to

Betelgeuse Betelgeuse is a red supergiant of spectral type M1-2 and one of the largest stars visible to the naked eye. It is usually the tenth-brightest star in the night sky and, after Rigel, the second-brightest in the constellation of Orion ...

although redder and more distant.

Description

119 Tauri has a

spectral class In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

of M2 and a

luminosity class In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the ...

of Iab-Ib, intermediate between an intermediate-luminosity supergiant and a less luminous supergiant. It is approximately 1,800

light years A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

from

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

, and with a

colour index In astronomy, the color index is a simple Numerical analysis, numerical Expression (mathematics), expression that determines the color of an object, which in the case of a star gives its temperature. The lower the color index, the more blue (or ...

of +2.07 it is one of the reddest naked eye stars in the night sky. 119 Tauri is classified as a semiregular

variable star A variable star is a star whose brightness as seen from Earth (its apparent magnitude) changes with time. This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as ...

and has been given the

variable star designation In astronomy, a variable star designation is a unique identifier given to variable stars. It uses a variation on the Bayer designation format, with an identifying label (as described below) preceding the Latin genitive of the name of the constell ...

CE Tauri. The

General Catalogue of Variable Stars The General Catalogue of Variable Stars (GCVS) is a list of variable stars. Its first edition, containing 10,820 stars, was published in 1948 by the Academy of Sciences of the USSR and edited by B. V. Kukarkin and P. P. Parenago. Second and thi ...

gives a magnitude range from +4.23 to +4.54 with a period of 165 days. Other published studies find poorly-defined periodicity, but with possible periods around 270 and 1,300 days. Its

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...

magnitude changes much less than the visual magnitude; the visual brightness changes are driven by changes in temperature which shift the proportion of

electromagnetic radiation In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic field, electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, inf ...

emitted in the visual range.

Occultations

CE Tauri lies 4.6 degrees off the

ecliptic The ecliptic or ecliptic plane is the orbital plane of the Earth around the Sun. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic again ...

. This makes it a candidate for

occultation An occultation is an event that occurs when one object is hidden from the observer by another object that passes between them. The term is often used in astronomy, but can also refer to any situation in which an object in the foreground blocks ...

s by the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

and (extremely rarely) by one of the bright planets. The star's angular diameter has been measured by lunar occultation, giving limb-darkened visible light angular diameters of , , and . An occultation has also been observed in

H-alpha H-alpha (Hα) is a specific deep-red visible spectral line in the Balmer series with a wavelength of 656.28 nm in air and 656.46 nm in vacuum; it occurs when a hydrogen electron falls from its third to second lowest energy level. H-alph ...

, giving a diameter of , which indicates that there is circumstellar hydrogen producing emission across at least that size, nearly twice the visible diameter.

Angular diameter

The angular diameter of 119 Tauri has also been measured directly by

VLBI Very-long-baseline interferometry (VLBI) is a type of astronomical interferometry used in radio astronomy. In VLBI a signal from an astronomical radio source, such as a quasar, is collected at multiple radio telescopes on Earth or in space. The ...

, leading to limb-darkened diameters of , , , , , . Although CE Tauri is classified as a pulsating variable, observations using the same equipment and wavelengths have not detected significant changes in the angular diameter over time. Reconstructed images of the surface show bright spots that are attributed to giant convection cells.

Properties

Angular diameter measurements can be combined with absolute observed fluxes to derive an accurate effective temperature, about 3,800 K for 119 Tauri. Combined with a distance, the linear size of the star can be calculated. CE Tauri is found to have a radius between . Then the bolometric luminosity is the star is found to be about . However, the distance to 119 Tauri is still only known approximately from its

Hipparcos ''Hipparcos'' was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial obj ...

parallax.

Gaia Data Release 2 The ''Gaia'' catalogues are star catalogues created using the results obtained by ''Gaia'' space telescope. The catalogues are released in stages that will contain increasing amounts of information; the early releases also miss some stars, especia ...

gives a distinctly larger parallax, but with even greater uncertainty and flagged as unreliable. 119 Tauri is a

pulsating star Stellar pulsations are caused by expansions and contractions in the outer layers as a star seeks to maintain equilibrium. These fluctuations in stellar radius cause corresponding changes in the luminosity of the star. Astronomers are able to ded ...

although the pulsation has not been clearly detected in direct angular measurements. Observations of TiO lines in its spectrum as its brightness changes show effective temperature changes up to . Calculating its physical properties shows that the bolometric luminosity and radius both change by about 10%, with the radius typically being larger at cooler temperatures. Comparison of its properties with stellar evolutionary tracks shows CE Tauri to have evolved from an initial mass of and to have a current mass of . An alternative interpretation of observations, under the assumption that CE Tauri is an

asymptotic giant branch The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars. This is a period of stellar evolution undertaken by all low- to intermediate-mass stars (about 0.5 to 8 solar masses) lat ...

(AGB) star, give it a current mass of and a luminosity of .

References

{{DEFAULTSORT:119 Tauri M-type supergiants Asymptotic-giant-branch stars Semiregular variable stars Taurus (constellation) BD+18 0875 Tauri, 119 036389 025945

1845 Events January–March * January 10 – Elizabeth Barrett receives a love letter from the younger poet Robert Browning; on May 20, they meet for the first time in London. She begins writing her ''Sonnets from the Portuguese''. * January 23 ...

Tauri, CE