HD 93250 is a highly luminous hot blue

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 ...

in the Carina Nebula in the

constellation Carina Carina ( ) is a constellation in the southern sky. Its name is Latin for the keel of a ship, and it was the southern foundation of the larger constellation of Argo Navis (the ship ''Argo'') until it was divided into three pieces, the other two b ...

Location

HD 93250 is one of the brightest stars in the region of the Carina Nebula. It is only 7.5 arc-minutes from the famous

Eta Carinae Eta Carinae (η Carinae, abbreviated to η Car), formerly known as Eta Argus, is a stellar system containing at least two stars with a combined luminosity greater than five million times that of the Sun, located around distant in t ...

2,350 and HD 93250 is considered to be a member of the same loose

open cluster An open cluster is a type of star cluster made of up 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 ...

Trumpler 16 Trumpler 16 (''Tr 16'') is a massive open cluster that is home to some of the most luminous stars in the Milky Way galaxy. It is situated within the Carina Nebula complex in the Carina–Sagittarius Arm, located approximately from Earth. The c ...

, although it appears closer to the more compact

Trumpler 14 Trumpler 14 (''Tr 14'') is an open cluster with a diameter of , located within the inner regions of the Carina Nebula, approximately from Earth. Together with the nearby Trumpler 16, they are the main clusters of the Carina OB1 stellar associat ...

. HD 93250 is in a region of the Carina Nebula with several bright stars, for example HD 93268 and HDE 303311, but relatively few faint stars. It has been proposed that these bright stars are the core of a separate cluster called Collinder 232, but the lack of any concentration of fainter stars in the area makes it more likely that Collinder 232 is not a real cluster and HD 93250 is just an outlying member of one of the more obvious clusters. Membership of Trumpler 16 constrains the distance and likely age of HD 93250.

Spectrum

Although HD 93250 is known to be a binary star, individual spectra of the two components have never been observed, but they are thought to be very similar. The spectral type of HD 93250 has variously been given as O5, O6/7, O4, and O3. It has sometimes been classified as a

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 ...

star and sometimes as a

giant star A giant star is a star with substantially larger radius and luminosity than a main sequence, main-sequence (or ''dwarf'') star of the same effective temperature, surface temperature.Giant star, entry in ''Astronomy Encyclopedia'', ed. Patrick Moo ...

. The Galactic O-Star Spectroscopic Survey has used it as the standard star for the newly created O4

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 type.

Binary

HD 93250 is the brightest x-ray source in the Carina Nebula. It has long been suspected that this is due to colliding winds in a close pair of hot luminous stars, but investigations have failed to show any significant

radial velocity The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the temporal rate of change, rate of change of the distance or Slant range, range between the two points. It is e ...

variations to support this. One calculated orbit suggests that a small inclination means the radial velocity changes due to orbital motion will be too small to resolve given the type of

spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors i ...

of the two stars. In 2010,

AMBER Amber is fossilized tree resin that has been appreciated for its color and natural beauty since Neolithic times. Much valued from antiquity to the present as a gemstone, amber is made into a variety of decorative objects."Amber" (2004). In Ma ...

interferometry Interferometry is a technique which uses the ''interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber opt ...

resolved HD 93250 into two separate stars. No relative motion or radial velocity variations could be detected and so the orbit and properties of the two stars is still uncertain. The

projected Projected is an American rock supergroup consisting of Sevendust members John Connolly and Vinnie Hornsby, Alter Bridge and Creed drummer Scott Phillips, and former Submersed and current Tremonti guitarist Eric Friedman. The band released t ...

separation of the stars is 1.5 mas, approximately 3.5

astronomical unit The astronomical unit (symbol: au, or or AU) is a unit of length, roughly the distance from Earth to the Sun and approximately equal to or 8.3 light-minutes. The actual distance from Earth to the Sun varies by about 3% as Earth orbits t ...

s. The two stars show no measurable colour difference and are both likely to be hot O stars with masses within 10% of each other.

Properties

The physical properties of HD 93250 have only been calculated on the assumption that it is a single star. The temperature is around 50,000 K and its luminosity around Calculations of the mass have shown discrepancies between spectroscopic models and evolutionary models, which may be resolved by analysis of two separate stars in the system.

References

{{DEFAULTSORT:HD 93250 Carina (constellation) Carina Nebula 093250 O-type subgiants Emission-line stars 052558 Durchmusterung objects Spectroscopic binaries