GRAVITY discovers new double star in Orion Trapezium Cluster

Theta¹ Orionis C (θ¹ Orionis C) is a member of the Trapezium

open cluster An open cluster is a type of star cluster made of tens to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way galaxy, and ...

that lies within the

Orion Nebula The Orion Nebula (also known as Messier 42, M42, or NGC 1976) is a diffuse nebula in the Milky Way situated south of Orion's Belt in the Orion (constellation), constellation of Orion, and is known as the middle "star" in the "sword" of Orion. It ...

. The star ''C'' is the most massive of the four bright stars at the heart of the cluster. It is an O class blue main sequence star with a B-type

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 ...

companion. Its high luminosity and large distance (about 1,500

light year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distance, astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by t ...

s) give it an apparent visible magnitude of 5.1. Theta¹ Orionis consists of multiple components, primarily the four stars of the Trapezium cluster, all within one arc-minute of each other. Theta² Orionis is a more distant grouping of three main stars plus several fainter companions, 1-2 arc-minutes from Theta¹. Theta¹ C is itself a binary of two massive stars, C1 and C2, plus a very close fainter companion apparently escaping the system. Theta¹ Orionis C1 is responsible for generating most of the

ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...

light that is slowly ionizing (and perhaps photoevaporating) the Orion Nebula. This UV light is also the primary cause of the glow that illuminates the Orion Nebula. The star emits a powerful

stellar wind A stellar wind is a flow of gas ejected from the stellar atmosphere, upper atmosphere of a star. It is distinguished from the bipolar outflows characteristic of young stars by being less collimated, although stellar winds are not generally spheri ...

that is a hundred thousand times stronger than the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

's, and the outpouring gas moves at 1,000 km/s. The primary has a strong dipolar

magnetic field A magnetic field (sometimes called B-field) is a physical field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular ...

with an intensity of . The field is inclined at an angle of to the rotation axis. Detected in 2002, this was the first O-type star found to have a magnetic field, and is most likely a fossil field. This field is confining the motion of the strong stellar wind, which should reduce the mass loss rate by 80%.

References

{{Stars of Orion Orionis, Theta1, C Orionis, 41, C Binary stars O-type main-sequence stars Orion (constellation) B-type main-sequence stars 037022

1895 Events January * January 5 – Dreyfus affair: French officer Alfred Dreyfus is stripped of his army rank and sentenced to life imprisonment on Devil's Island (off French Guiana) on what is much later admitted to be a false charge of tr ...

Durchmusterung objects 026221