θ¹ Orionis E (Latinised as Theta¹ Orionis E) is a double-lined

spectroscopic binary A binary star or binary star system 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 as separate stars us ...

located 4' north of θ¹ Orionis A in the

Trapezium Cluster The Trapezium or Orion Trapezium Cluster, also known by its Bayer designation of Theta1 Orionis (θ1 Orionis), is a tight open cluster of stars in the heart of the Orion Nebula, in the constellation of Orion. It was discovered by Galileo Galile ...

. The two components are almost identical

pre-main-sequence star A pre-main-sequence star (also known as a PMS star and PMS object) is a star in the stage when it has not yet reached the main sequence. Earlier in its life, the object is a protostar that grows by acquiring mass from its surrounding envelope o ...

s in a close circular orbit, and they show shallow eclipses that produce brightness variations of a few tenths of a magnitude. Theta1OriELightCurve

Each component of the binary system is slightly under . Although they have a

subgiant A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution ...

spectral classification, they are still contracting onto the

main sequence In astronomy, the main sequence is a classification of stars which appear on plots of stellar color index, color versus absolute magnitude, brightness as a continuous and distinctive band. Stars on this band are known as main-sequence stars or d ...

and are estimated to be only about 500,000 years old. It is estimated that they will reach the main sequence as smaller hotter late-B stars. The variability was first reported in 1954 and confirmed as an eclipsing binary in 2012. It has not been assigned a

variable star designation In astronomy, a variable-star designation is a unique identifier given to variable stars. It extends the Bayer designation format, with an identifying label (as described below) preceding the Latin genitive of the name of the constellation in whic ...

but is listed in the

New Catalogue of Suspected Variable Stars The ''New Catalogue of Suspected Variable Stars'' (NSV) is a star catalogue A star catalogue is an astronomical catalogue that lists stars. In astronomy, many stars are referred to simply by catalogue numbers. There are a great many different ...

References

{{DEFAULTSORT:Theta1 Orionis E Orion (constellation) G-type subgiants 5 J05351577-0523100 Orionis, Theta1E Orionis, 41 E