SY Muscae is a

binary star 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 ...

system in the

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 ...

Musca composed of a

red giant A red giant is a luminous giant star of low or intermediate mass (roughly 0.3–8 solar masses ()) in a late phase of stellar evolution. The outer atmosphere is inflated and tenuous, making the radius large and the surface temperature around or ...

and a white dwarf. Its apparent magnitude varies from 10.2 to 12.7 over a period of 624.5 days. Although the binary is a

symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...

star system, it is unusual in that it does not have an eruptive component. It is an S-type symbiotic system, which means that the light comes from the stars rather than surrounding dust. With optical spectrometry, the red giant has been calculated as having a surface temperature of 3500 K and spectral type M4.5III, with around 1.3 times the Sun's mass, 86 times its radius and 1000 times its

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 ...

. The white dwarf is only 0.43 times the mass of the Sun. The two stars are 1.72 astronomical units (AU) apart, and take 624 days to orbit each other. The red giant also pulsates with a period of 56 days. The surface of the giant star extends to 40% of the distance to the Lagrange point L₁, and hence does not fill its Roche Lobe and cause the white dwarf to gain an accretion disc. The system was calculated at being around 850 parsecs (2771

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 1012 ...

s) distant.

References

{{DEFAULTSORT:SY Muscae Musca Muscae, SY M-type giants White dwarfs Z Andromedae variables Durchmusterung objects 100336 Semiregular variable stars