R Fornacis is a Mira variable and

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 mo ...

located in the constellation

Fornax Fornax () is a constellation in the southern celestial hemisphere, partly ringed by the celestial river Eridanus. Its name is Latin for furnace. It was named by French astronomer Nicolas Louis de Lacaille in 1756. Fornax is one of the 88 mod ...

. It is around away based on

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or semi-angle of inclination between those two lines. Due to foreshortening, nearby object ...

measurements. R Fornacis is a carbon star, a star on the

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 ...

with an excess of carbon over oxygen in its atmosphere due to fusion products being dredged up to the surface from deep inside the star. It is also a Mira variable, a type of pulsating

giant star A giant star is a star with substantially larger radius and luminosity than a main-sequence (or ''dwarf'') star of the same surface temperature.Giant star, entry in ''Astronomy Encyclopedia'', ed. Patrick Moore, New York: Oxford University Press ...

which varies by several

apparent 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 li ...

s with a period of a few hundred days. R Fornacis has a period of 389 days and varies between extremes of magnitude 7.5 and 13.0, although average maximum and minimum magnitudes are 8.9 and 12.2 respectively.. R Fornacis was discovered to be variable in 1896 after it had been observed with a different brightness to that shown in the Cordoba Durchmusterung. In 1983, an unusually deep minimum was observed, and later correlated with an asymmetric shell of material ejected from the surface of the star. Unconfirmed visual estimates of the unusual minimum give a magnitude of 14.0, while infrared observations confirm the unusual variation.

References

{{DEFAULTSORT:R Fornacis Mira variables Carbon stars Fornax Fornacis, R IRAS catalogue objects J02291531-2605559 Emission-line stars Durchmusterung objects