RS Telescopii, abbreviated RS Tel, is a

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 ...

in the southern

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 ...

Telescopium Telescopium is a minor constellation in the southern celestial hemisphere, one of twelve named in the 18th century by French astronomer Nicolas-Louis de Lacaille and one of several depicting scientific instruments. Its name is a Latinized for ...

. It is a dim star with an

apparent visual magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's lig ...

of 10.67, which is much too faint to be visible without a telescope. The variability of this star was discovered by Evelyn F. Leland and announced by

Edward C. Pickering Edward Charles Pickering (July 19, 1846 – February 3, 1919) was an American astronomer and physicist and the older brother of William Henry Pickering. Along with Hermann Carl Vogel, Carl Vogel, Pickering discovered the first spectroscopic binary ...

in 1910. It was first studied by Cecilia H. Payne in 1928 at the

Harvard College Observatory The Harvard College Observatory (HCO) is an institution managing a complex of buildings and multiple instruments used for astronomical research by the Harvard University Department of Astronomy. It is located in Cambridge, Massachusetts, United St ...

. This is an R-type

carbon star A carbon star (C-type star) is typically an asymptotic giant branch star, a luminous red giant, whose atmosphere contains more carbon than oxygen. The two elements combine in the upper layers of the star, forming carbon monoxide, which consumes mos ...

with a

class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differentl ...

of R0. RS Tel is a typical

R Coronae Borealis variable An R Coronae Borealis variable (abbreviated RCB, R CrB) is an eruptive variable star that varies in luminosity in two modes, one low amplitude pulsation (a few tenths of a magnitude), and one irregular, unpredictably-sudden fading by 1 to 9 ma ...

—an extremely hydrogen-deficient

supergiant Supergiants are among the most massive and most luminous stars. Supergiant stars occupy the top region of the Hertzsprung–Russell diagram with absolute visual magnitudes between about −3 and −8. The temperature range of supergiant stars spa ...

thought to have arisen as the result of the merger of two

white dwarf A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes fro ...

s; fewer than 100 have been discovered as of 2012. It has under 55% the mass of the Sun and an

effective temperature The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature ...

of around 5,800 K. The

spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors i ...

of the star shows anomalously weak

lines Line most often refers to: * Line (geometry), object with zero thickness and curvature that stretches to infinity * Telephone line, a single-user circuit on a telephone communication system Line, lines, The Line, or LINE may also refer to: Arts ...

of hydrogen, with strong lines of C₂, CN, and neutral

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...

. RS Tel has a maximum

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

of 9.6 and a minimum magnitude 16.5. The star undergoes large, random variations in brightness on a time scale of thousands of days with no apparent periodicity. The star is surrounded by a circumstellar shell of dust which radiating an

infrared excess An infrared excess is a measurement of an astronomical source, typically a star, that in their spectral energy distribution has a greater measured infrared flux than expected by assuming the star is a blackbody radiator. Infrared excesses are o ...

References

{{DEFAULTSORT:RS Telescopii Carbon stars R Coronae Borealis variables Telescopium (constellation) CD-46 12279 089739 Telescopii, RS TIC objects