S Antliae is a

W Ursae Majoris W Ursae Majoris (W UMa) is the variable star designation for a binary star system in the northern constellation of Ursa Major. It has an apparent visual magnitude of about 7.9, which is too faint to be seen with the naked eye. However, i ...

-type

eclipsing binary A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in wh ...

star in

Antlia Antlia (; from Ancient Greek ''ἀντλία'') is a constellation in the Southern Celestial Hemisphere. Its name means " pump" in Latin and Greek; it represents an air pump. Originally Antlia Pneumatica, the constellation was established by N ...

Characteristics

S Antilia is classed as an A-type W Ursae Majoris variable, since the primary is hotter than the secondary and the drop in magnitude is caused by the latter passing in front of the former. S Antilia varies in apparent magnitude from 6.27 to 6.83 over a period of 15.6 hours. The system shines with a combined spectrum of A9V. The system's orbital period is 0.648 days. The stars' centres are an average of 3.31 times the sun's radius apart, which places their surfaces just 3.4 times the sun's radius apart. Thus, the two stars will eventually merge to form a single fast-spinning star. Calculating the properties of the component stars from the orbital period indicates that the primary star has a mass 0.79 times and a diameter 1.46 times that of the Sun, and the secondary has a mass 0.47 times and a diameter 1.13 times that of the Sun. The primary has a surface temperature of 7800 K, while the secondary is a little cooler at 7340 K. The two stars have similar

luminosity Luminosity is an absolute measure of radiated electromagnetic power (light), the radiant power emitted by a light-emitting object over time. In astronomy, luminosity is the total amount of electromagnetic energy emitted per unit of time by a st ...

and

spectral type In astronomy, stellar classification is the classification of stars based on their stellar spectrum, spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a Prism (optics), prism or diffraction grati ...

as they have a

common envelope In astronomy, a common envelope (CE) is gas that contains a binary star system. The gas does not rotate at the same rate as the embedded binary system. A system with such a configuration is said to be in a common envelope phase or undergoing commo ...

and share stellar material. The system is thought to be around two billion years old. Based upon an annual

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 objects ...

shift of 11.84 milli

arc second A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The na ...

s as measured by the

Hipparcos ''Hipparcos'' was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial obj ...

satellite, this system is from

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 surfa ...

. Analysing and recalibrating yields a parallax of 13.30 and hence a distance of .

History

The star's variability was first recorded in 1888 by H.M. Paul, when it had the shortest known period of any variable star. It was initially thought to be an

Algol ALGOL (; short for "Algorithmic Language") is a family of imperative computer programming languages originally developed in 1958. ALGOL heavily influenced many other languages and was the standard method for algorithm description used by the ...

-type eclipsing binary, but this was discounted by E.C. Pickering on account of it lacking a shallow minimum in its maximum and the width of its minimum period.

Alfred H. Joy Alfred Harrison Joy (September 23, 1882 in Greenville, Illinois – April 18, 1973 in Pasadena, California) was an astronomer best known for his work on stellar distances, the radial motion of stars, and variable stars. A Joy (crater), crater on ...

noted the similarity of its light curve to

in 1926, concluding the system was indeed an eclipsing binary with two stars of spectral type A8.

References

{{DEFAULTSORT:S Antliae Antlia 082610 W Ursae Majoris variables Antliae, S 3798 046810 Durchmusterung objects A-type main-sequence stars