Scientists observed X-ray emission of the most luminous quasar

An X-ray look at the heart of powerful quasars.


The fall of gas into a supermassive black hole powers quasars among the brightest and farthest objects in the known Universe. They can be considered highly bright active galactic nuclei (AGN) that produce enormous amounts of electromagnetic radiation that can be seen at wavelengths in the radio, infrared, visible, ultraviolet, and X-ray ranges.

The most luminous quasar in the previous 9 billion years of cosmic history, SMSS J114447.77-430859.3, or J1144 for short, has been observed emitting X-rays. The new perspective clarifies quasars‘ inner workings and interactions with their surroundings.

J1144, located between the constellations of Centaurus and Hydra and hosted by a galaxy 9.6 billion light-years from Earth, is incredibly powerful, glowing 100,000 billion times brighter than the sun. Astronomers can learn more about the quasar’s black hole and its surroundings thanks to J1144’s proximity to Earth compared to other objects of the same intensity.

For this study, researchers combined data from various space-based observatories, including NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR), the ESA’s XMM-Newton observatory, the Spectrum-Roentgen-Gamma (SRG) observatory’s eROSITA instrument, and NASA’s Neil Gehrels Swift observatory.

The scientists measured the temperature of the X-rays being released from the quasar using the data from the four observatories. They discovered that this temperature was close to 350 million Kelvin, which is more than 60,000 times hotter than the temperature on the sun’s surface. The scientists also discovered that the black hole at the center of the quasar has a mass roughly 10 billion times that of the sun and is expanding at about 100 solar masses per year.

This source produced X-ray radiation that changed over a few days, which is unusual for quasars with black holes the size of the one seen in J1144. For a black hole of this size, the normal timescale of variability would be on the order of months or even years. The observations also revealed that while the black hole sucks up some of the gas, some is released by strong winds that release a significant amount of energy into the host galaxy.

Dr. Kammoun, lead author of the paper, says, “We were very surprised that no prior X-ray observatory has ever observed this source despite its extreme power.”

He adds, “Similar quasars are usually found at much larger distances, so they appear much fainter, and we see them as they were when the Universe was only 2-3 billion years old. J1144 is a rare source as it is so luminous and much closer to Earth (although still at a huge distance!), giving us a unique glimpse of what such powerful quasars look like.”

“A new monitoring campaign of this source will start in June this year, which may reveal more surprises from this unique source.”

Journal Reference:

  1. E S Kammoun et al., The first X-ray look at SMSS J114447.77-430859.3: the most luminous quasar in the last 9 Gyr, Monthly Notices of the Royal Astronomical Society (2023). DOI: 10.1093/mnras/stad952


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