119 Tauri

119 Tauri (also known as CE Tauri) is a star in the constellation Taurus. It has a diameter about 590 times that of the Sun. CE Tauri is close enough that its distance can be determined accurately by parallax and so the actual diameter can be determined directly from the angular diameter.

119 Tauri has a spectral class of M2 and a luminosity class of Iab-Ib, intermediate between an intermediate-luminosity supergiant and a less luminous supergiant. It is approximately 1,800 light years from Earth. The star is classified as a semiregular variable star and its brightness varies from magnitude +4.23 to +4.54 with a period of 165 days. With a colour index of +2.07, it is one of the reddest naked eye stars in the night sky.

CE Tauri lies 4.6 degrees off the ecliptic. This makes it a candidate for occultations by the Moon 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 $14.37$, $0.05$, and $13.9$. An occultation has also been observed in H-alpha, giving a diameter of $9.1 mas$, which indicates that there is circumstellar hydrogen producing emission across at least that size, nearly twice the visible diameter.

The angular diameter has also been measured directly by VLBI, leading to limb-darkened diameters of $10.9 mas$, $9 mas$, $17 mas$, $10.68 mas$,, $9.83 mas$, $9.3 mas$. 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.

Angular diameter measurements can be combined with absolute observed fluxes to derive an accurate effective temperature, in this case about 3,800 K. Combined with a distance, the linear size of the star can be calculated. CE Tauri is found to have a radius of around. Then the bolometric luminosity is the star is found to be about. Comparison 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 (AGB) star, give it a current mass of and a luminosity of.