NuSTAR Bringing the High Energy Universe into Focus

Researchers have observed the X-ray emission of the most luminous quasar seen in the last 9 billion years of cosmic history. The new perspective sheds light on the inner workings of quasars and how they interact with their environment.

Hosted by a galaxy 9.6 billion light years away from the Earth, between the constellations of Centaurus and Hydra, the quasar SMSS J114447.77-430859.3, or J1144 for short, is extremely powerful, shining 100,000 billion times brighter than the Sun. J1144 is much closer to Earth than other sources of the same luminosity, allowing astronomers to gain insight into the black hole powering the quasar and its surrounding environment. The study was led by Dr Elias Kammoun, a postdoctoral researcher at the Research Institute in Astrophysics and Planetology (IRAP), and Zsofi Igo, a PhD candidate at the Max Planck Institute for Extraterrestrial Physics (MPE).

Quasars are among the brightest and most distant objects in the known universe, powered by the fall of gas into a supermassive black hole.  The material becomes very hot as it comes close to the black hole, causing quasars to shine brightly from X-ray to radio energies.  J1144 was first discovered in 2022 from its optical light by the SkyMapper Southern Survey (SMSS).

For this study, researchers combined observations from several space-based observatories: NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) observed the quasar in the high-energy, or hard X-ray band, while NASA's Neil Gehrels Swift observatory, ESA's XMM-Newton observatory, and the eROSITA instrument on board the Spectrum-Roentgen-Gamma (SRG) observatory observed the quasar in the low-energy, or soft X-ray band.  Together, the broad-band X-ray data from these combined observations provide an unprecedented view into the properties of this extreme source.

The team used the data from the four observatories to measure the temperature of the X-rays being emitted from the quasar. They found this temperature to be around 350 million Kelvin, more than 60,000 times the temperature at the surface of the Sun. The team also found that the mass of the black hole at the quasar's centre is around 10 billion times the mass of the Sun, and the rate at which it is growing to be of the order of 100 solar masses per year.

The X-ray light from this source varies on a time scale of a few days, which is not usually seen in quasars with black holes as large as the one residing in J1144. Typically, larger black holes vary less than smaller black holes, and a black hole of this size would be expected to vary on month to year timescales. The observations also showed that while a portion of the gas is swallowed by the black hole, some gas is ejected in the form of extremely powerful winds, injecting large amounts of energy into the host galaxy.

Dr. Kammoun, lead author of the paper, says "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 very 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."

Dr. Kammoun adds "A new monitoring campaign of this source will start in June this year, which may reveal more surprises from this unique source."

A Small Explorer mission led by Caltech and managed by NASA’s Jet Propulsion Laboratory in Southern California for the agency’s Science Mission Directorate in Washington, NuSTAR was developed in partnership with the Danish Technical University and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corp. in Dulles, Virginia. NuSTAR’s mission operations center is at the University of California, Berkeley, and the official data archive is at NASA’s High Energy Astrophysics Science Archive Research Center at NASA’s Goddard Space Flight Center. ASI provides the mission’s ground station and a mirror data archive. Caltech manages JPL for NASA.