UZ Pyxidis (HD 75021) is a semiregular variable

star A star is an astronomical object comprising a luminous spheroid of plasma held together by its gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night, but their immense distances from Earth make ...

in the constellation

Pyxis Pyxis is a small and faint constellation in the southern sky. Abbreviated from Pyxis Nautica, its name is Latin for a mariner's compass (contrasting with Circinus, which represents a draftsman's compasses). Pyxis was introduced by Nicolas-Louis ...

. It is located about 3,600

light-year 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 101 ...

s (1,100

parsec The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (au), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, a ...

s) away from the

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 surf ...

. UZ Pyxidis lies directly between α and γ Pyxidis. It has a

common proper motion This glossary of astronomy is a list of definitions of terms and concepts relevant to astronomy and cosmology, their sub-disciplines, and related fields. Astronomy is concerned with the study of celestial objects and phenomena that originate outsi ...

companion, HD 75022, less than 2' away but the two are not listed in double star catalogues. UZ Pyxidis is a

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 ...

. These types of stars are known for having large amounts of

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon makes ...

in their atmospheres, forming carbon compounds that make the star appear strikingly red. It was first recognised as having an unusual spectrum in 1893. Under the Morgan–Keenan classification of carbon stars, UZ Pyxidis'

spectral type 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 th ...

is C5₅; if it were a normal

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 ...

, this would correspond to a spectral type of about K5. It is also unusual in that it has very strong isotopic bands of C₂ and CN. UZ Pyxidis is classified as 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 ...

with a dominant period of 159.6 days. It varies in brightness between

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 ...

6.99 and 7.63. The variability was first reported in 1972, and 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 constel ...

UZ Pyxidis was assigned in 1978.

References

{{DEFAULTSORT:UZ Pyxidis Pyxis Semiregular variable stars Pyxidis, UZ 075021 043093 CD-29 06735 Carbon stars