A team of scientists led by Caltech has discovered evidence for this event taking place within a quasar, a very powerful object.

Quasars are galaxies’ active cores, where a supermassive black hole is sucking material from a disk that surrounds it. The supermassive black hole in some quasars produces a jet that travels at almost the speed of light.

PKS 2131-021, the quasar observed in the current study, belongs to a subclass of quasars known as blazars, which have a jet pointed toward Earth. Quasars are known to have two supermassive black holes surrounding them, but obtaining direct proof for this has been challenging.

The researchers claim that PKS 2131-021 is now the second known possibility for a pair of supermassive black holes in the process of merging, as reported in The Astrophysical Journal Letters. Within a quasar known as OJ 287, the first candidate pair orbits each other at a greater distance, looping every nine years rather than the two years it takes the PKS 2131-021 pair to complete an orbit.

The convincing proof comes from 45 years of radio monitoring of PKS 2131-021. According to the research, due to the pair’s orbital motion, a tremendous jet emerging from one of the two black holes within PKS 2131-021 is changing back and forth. The radio-light brightness of the quasar changes on a regular basis as a result of this. 

The combination of the radio data results in a virtually perfect sinusoidal light curve, unlike anything previously observed from quasars.

“When we realized that the peaks and troughs of the light curve detected from recent times matched the peaks and troughs observed between 1975 and 1983, we knew something very special was going on,” says Sandra O’Neill, lead author of the new study.

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Image Credit: Caltech

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