GCIRS 16SW, also known as S97, is a

contact binary In astronomy, a contact binary is a binary star system whose component stars are so close that they touch each other or have merged to share their gaseous envelopes. A binary system whose stars share an envelope may also be called an overcontac ...

star located in the

Galactic Center The Galactic Center is the barycenter of the Milky Way and a corresponding point on the rotational axis of the galaxy. Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A*, a ...

. It is composed of two hot massive stars of equal size that orbit each other with a period of 19.5 days. The stars are so close that their atmospheres overlap, and the two stars form an

eclipsing binary A binary star or binary star system is a Star system, system of two stars that are gravity, 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 ...

varying in brightness by 0.35 magnitudes at

infrared Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...

wavelengths. GCIRS 16SW Celestia

GCIRS 16SW orbits

Sagittarius A* Sagittarius A*, abbreviated as Sgr A* ( ), is the supermassive black hole at the Galactic Center of the Milky Way. Viewed from Earth, it is located near the border of the constellations Sagittarius and Scorpius, about 5.6° south o ...

at approximately 19,000 AU, with a period of approximately 1,270 years. At the stars' estimated mass of about 50

solar mass The solar mass () is a frequently used unit of mass in astronomy, equal to approximately . It is approximately equal to the mass of the Sun. It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxie ...

es, they are predicted to have a lifespan of about 4 million years, indicating that the system formed within of Sagittarius A*, instead of having migrated inward from a greater distance. GCIRS 16SW was classified as a candidate

luminous blue variable Luminous blue variables (LBVs) are rare, massive, evolved stars that show unpredictable and sometimes dramatic variations in their spectra and brightness. They are also known as S Doradus variables after S Doradus, one of the brightest stars of th ...

on the basis of its spectrum and physical properties. This was before it was identified as an eclipsing binary, but it is still treated as a candidate LBV. Each star is strongly distorted by the gravity of the other star. The polar radius is calculated to be , while the radius along the direction of orbital motion is . The radius along the line joining the two stars is , while the separation of the centres of the two stars is . A calculation of properties treating the binary as a single star gave an

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 ...

of . The secondary component is found to have a temperature 96% of that of the primary. However, these temperatures yield a luminosity over a million times that of the sun, uncomfortably close to the

Eddington luminosity The Eddington luminosity, also referred to as the Eddington limit, is the maximum luminosity a body (such as a star) can achieve when there is balance between the force of radiation acting outward and the gravitational force acting inward. The stat ...

for each star, and it is suspected the actual temperatures are slightly lower.

References

{{DEFAULTSORT:GCIRS 16SW Sagittarius (constellation) Galactic Center O-type supergiants Wolf–Rayet stars Eclipsing binaries