TU Muscae, also known as HD100213, is an eclipsing binary

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

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. Its apparent magnitude ranges from 8.17 to 8.75 over around 1.4 days.

Physical description

TU Muscae is a remote

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 made up of two hot luminous blue main sequence stars of spectral types O7.5V and O9.5V, with masses 23 and 15 times that of the Sun. The stars are so close that they are in contact with each other ( overcontact binary) and are classed as a Beta Lyrae variable as their light varies from earth as they eclipse each other. The spectra indicate they are hot stars, with surface temperatures of roughly 37200 and 34700 K respectively. They are both still on the

main sequence In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Her ...

of star evolution, burning their core hydrogen. Astronomers Laura Penny and Cynthia Ouszt proposed the two were originally more equal in size but as they became close enough so that material from the less massive star began transferring to the more massive star via Roche-lobe overflow. However they concede that figuring out the evolution of interacting massive binary systems is "a little like trying to unspill milk". The system is thought to be around 4.8 kiloparsecs (~15500 light-years) distant. The period of the magnitude change is increasing, and has been calculated as lengthening by 3.46 seconds a century. This could be due to material from the less massive star being transferred to the more massive one, or there could be a third or fourth as yet undetected star in the multiple star system influencing the orbit. These stars have not been seen as they are much less luminous than the two main stars.

Discovery

TU Muscae was discovered by Dutch astronomer

Pieter Oosterhoff Pieter Theodorus Oosterhoff (30 March 1904, Leeuwarden - 14 March 1978, Leiden) was a Dutch astronomer. He was the co-administrator, along with Jan Oort, of the Leiden Observatory in the Netherlands. His published papers are primarily in regard ...

in 1928. Initially thought to have a spectrum of B3, later observations in the 1960s and early 1970s indicated it was a hotter star than previously thought—with the spectrum lying in the uncommon O-region.

References

{{DEFAULTSORT:TU Muscae Beta Lyrae variables Musca O-type main-sequence stars Spectroscopic binaries Muscae, TU 100213 056196 J11311091-6544322 Durchmusterung objects