R Trianguli (abbreviated as R Tri) is a short-period

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as we ...

-rich

Mira variable Mira variables (named for the prototype star Mira) are a class of pulsating stars characterized by very red colours, pulsation periods longer than 100 days, and amplitudes greater than one magnitude in infrared and 2.5 magnitude at visual wave ...

Triangulum Triangulum is a small constellation in the northern sky. Its name is Latin for " triangle", derived from its three brightest stars, which form a long and narrow triangle. Known to the ancient Babylonians and Greeks, Triangulum was one of the 4 ...

with a period of 266.9 days, discovered by

T. H. E. C. Espin The Reverend Thomas Henry Espinell Compton Espin or T. H. E. C. Espin (28 May 1858 – 2 December 1934) was a British astronomer. His father Thomas Espin was Chancellor of the Diocese of Chester and his mother was Elizabeth (née Jessop). He ...

in 1890. It is losing about , close to average for a short-period Mira variable. While most short-period Mira variables reside in the

Galactic halo A galactic halo is an extended, roughly spherical component of a galaxy which extends beyond the main, visible component. Several distinct components of galaxies comprise the halo: * the stellar halo * the galactic corona (hot gas, i.e. a plas ...

, R Trianguli is a member of the

thick disk The thick disk is one of the structural components of about 2/3 of all disk galaxies, including the Milky Way. It was discovered first in external edge-on galaxies. Soon after, it was proposed as a unique galactic structure in the Milky Way, diff ...

, and its proper motion is fairly high for its distance. Its

angular diameter The angular diameter, angular size, apparent diameter, or apparent size is an angular distance describing how large a sphere or circle appears from a given point of view. In the vision sciences, it is called the visual angle, and in optics, it i ...

in the K band was measured in 2002 to be, on average, , with a shape suggesting that there is an optically thin disk structure surrounding the star. RTriLightCurve

References

{{Triangulum Mira variables M-type giants Trianguli, R Triangulum Astronomical objects discovered in 1890 0758 016210 J02370234+3415513 Emission-line stars 012193