A rare spectacle of a pair of quasars shining brightly at the center of merging galaxies in the early universe, only about 3 billion years after the Big Bang, has been observed and reported to the scientific community. Quasars, also known as quasi-stellar objects or “quasistars,” shine brightly like stars but are even brighter than their host galaxies due to the accretion of matter onto supermassive black holes.
The quasars were discovered in a pair located at the center of a large elliptical galaxy in the process of merging with another galaxy, with the supermassive black holes at their centers drawing material closer and closer together in preparation for their eventual merger. The research team, led by a University of Illinois astronomer, confirmed the existence of the pair of quasars using a variety of telescopes, including the Hubble Space Telescope, the Gaia satellite, the Gemini North telescope, the Chandra X-ray Observatory, and the Karl G. Jansky Very Large Array.
The confirmation process was challenging, requiring a range of electromagnetic wave telescopes from X-rays to radio waves to determine that the two objects were indeed a pair of quasars and not just a gravitational lensing effect. The researchers note that finding these closely-spaced, accreting supermassive black holes in merging galaxies in the early universe is akin to finding a needle in a haystack.
While pairs of black holes have been observed in merging galaxies before, this is the first time that a pair of supermassive black holes in the form of quasars has been observed in the same galaxy during the “cosmic noon” period, about 3 billion years after the Big Bang when stars were being actively formed. The close spacing of the quasars, only about 10,000 light-years apart, indicates that the galaxies were well into the merger process at this time.
The lead author of the paper notes that this observation provides a glimpse into the early stages of pair quasars and can help develop methods for finding more pairs of quasars that are close enough together to be observed.