μ Orionis (Latinised to Mu Orionis, abbreviated to μ Ori or Mu Ori) is a quadruple star system in the constellation Orion, similar to

Mizar Mizar is a second-magnitude star in the handle of the Big Dipper asterism in the constellation of Ursa Major. It has the Bayer designation ζ Ursae Majoris ( Latinised as Zeta Ursae Majoris). It forms a well-known naked eye d ...

and

Epsilon Lyrae Epsilon Lyrae (ε Lyr, ε Lyrae), also known as the Double Double, is a multiple star system of at least five stars approximately 162 light-years away in the constellation of Lyra. Star system The widest two components of the system ...

with combined visual magnitude of 4.13. The four stars are known as Mu Orionis Aa, Mu Orionis Ab, Mu Orionis Ba, and Mu Orionis Bb. The A and B systems are several tenths of an

arcsecond 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 ...

apart. The entire system is located approximately 150

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 from the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

. Mu Orionis Aa is an A5V dwarf and metallic line star, of

effective temperature The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation. Effective temperature is often used as an estimate of a body's surface temperature ...

, and

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 ...

of +4.31. Mu Orionis Aa has 2.1 solar masses, and a radius of and a luminosity 32 times that of the Sun. Mu Orionis Ab is a G5V dwarf orbiting Aa at a distance of , 0.2x the orbit of

Mercury Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...

. Mu Orionis Ba and Bb are F5V dwarfs with 1.4

solar mass The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...

es and apparent magnitudes of 6.91. They are separated from each other by . μ Orionis falls just outside an unrelated

planetary nebula A planetary nebula (PN, plural PNe) is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives. The term "planetary nebula" is a misnomer because they are unrelated to ...

Abell 12. The bright star makes detecting the faint nebula difficult and it has been nicknamed The Hidden.

References

External links

* http://stars.astro.illinois.edu/sow/muori.html {{DEFAULTSORT:Mu Orionis Orion (constellation) Orionis, Mu 4 A-type main-sequence stars F-type main-sequence stars G-type main-sequence stars Spectroscopic binaries Orionis, 61 2124 040932 028614 Durchmusterung objects J05351889-0516140 Am stars