PKS 1302−102 is a

quasar A quasar ( ) is an extremely Luminosity, luminous active galactic nucleus (AGN). It is sometimes known as a quasi-stellar object, abbreviated QSO. The emission from an AGN is powered by accretion onto a supermassive black hole with a mass rangi ...

in the Virgo constellation, located at a distance of approximately 1.1

Gpc GPC may refer to: Businesses and organisations Politics * General People's Congress (disambiguation) * Goa People's Congress, in India * Green Party of Canada * Group of Cameroonian Progressives Other businesses and organisations * Genuine ...

(around 3.5 billion light-years). It has an

apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

of about 14.9 mag in the

V band The V band ("vee-band") is a standard designation by the Institute of Electrical and Electronics Engineers (IEEE) for a band of frequencies in the microwave portion of the electromagnetic spectrum ranging from 40 to 75 gigahertz (GHz). The ...

with a

redshift In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decrease in wavelength and increase in frequency and e ...

of 0.2784. The quasar is hosted by a bright

elliptical galaxy An elliptical galaxy is a type of galaxy with an approximately ellipsoidal shape and a smooth, nearly featureless image. They are one of the three main galaxy morphological classification, classes of galaxy described by Edwin Hubble in his Hub ...

, with two neighboring companions at distances of 3 kpc and 6 kpc. The light curve of PKS 1302−102 appears to be sinusoidal with an amplitude of 0.14 mag and a period of 1,884 ± 88 days, which suggests evidence of a supermassive black hole binary.

Possible black hole binary

PKS 1302−102 was selected from the

Catalina Real-Time Transient Survey The Catalina Real-Time Transient Survey is a collaboration using three telescopes looking for optical transients. The same telescopes are used as in the Catalina Sky Survey. They are Mt. Lemmon Survey, Catalina Sky Survey, and Siding Spring Surv ...

as one of 20 quasars with apparent periodic variations in the light curve. Of these quasars, PKS 1302−102 appeared to be the best candidate in terms of sinusoidal behavior and other selection criteria, such as data coverage of more than 1.5 cycles in the measured period. One plausible interpretation of the apparent periodic behavior is the possibility of two

supermassive black holes A supermassive black hole (SMBH or sometimes SBH) is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions, of times the mass of the Sun (). Black holes are a class of astronomical o ...

(SMBH) orbiting each other with a separation of approximately 0.1 pc in the final stages of a 3.3 billion year old galaxy merger. If this turns out to be the case, it would make PKS 1302−102 an important object of study to various areas of research, including

gravitational wave Gravitational waves are oscillations of the gravitational field that Wave propagation, travel through space at the speed of light; they are generated by the relative motion of gravity, gravitating masses. They were proposed by Oliver Heaviside i ...

studies and the unsolved final parsec problem in a merger of black holes. Other explanations, of lesser likelihood, to the observed sinusoidal periodicity include a hot spot on the inner part of the black hole's accretion disk and the possibility of a warped accretion disk which partially eclipses in the orbit around a single SMBH. However, it also remains possible that the periodic behavior in PKS 1302−102 is indeed just a random occurrence in the light curve of an ordinary quasar, as

spurious Spurious may refer to: * Spurious relationship in statistics * Spurious emission or spurious tone in radio engineering * Spurious key in cryptography * Spurious interrupt in computing * Spurious wakeup in computing * ''Spurious'', a 2011 no ...

nearly-periodic variations can occur over limited time periods as part of stochastic quasar variability. Further observations of the quasar could either promote true periodicity or rule out a binary interpretation, especially if the measured light curve randomly diverges from the sinusoidal model.

Possible black hole binary

References

Further reading