Why are Some Quasars So Lonely?

This image, taken by NASA’s James Webb Space Telescope, shows an ancient quasar (circled in red) with fewer than expected neighboring galaxies (bright spheres), challenging physicists’ understanding of how the first quasars and supermassive black holes formed. Credits:Credit: Christina Eilers/EIGER team

At the centre of most galaxies are supermassive black holes. When they are ‘feeding’ they blast out jets of material with associated radiation that can outshine the rest of the galaxy. These are known as quasars and they are usually found in regions where huge quantities of gas exist. However, a recent study found a higher than expected number of quasars that are alone in the Universe. These loners are not surrounded by galaxies nor a supply of gas. The question therefore remains, how are they shining so brightly. 

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Early Black Holes Fed 40x Faster than Should Be Possible

This artist’s illustration shows a red, early-Universe dwarf galaxy that hosts a rapidly feeding black hole at its center. Using data from NASA's JWST and Chandra X-ray Observatory, a team of U.S. National Science Foundation NOIRLab astronomers have discovered this low-mass supermassive black hole at the center of a galaxy just 1.5 billion years after the Big Bang. It is accreting matter at a phenomenal rate — over 40 times the theoretical limit. While short lived, this black hole’s ‘feast’ could help astronomers explain how supermassive black holes grew so quickly in the early Universe.

The theory goes that black holes accrete material, often from nearby stars. However the theory also suggests there is a limit to how big a black hole can grow due to accretion and certainly shouldn’t be as large as they are seen to be in the early Universe. Black holes it seems, are fighting back and don’t care about those limits! A recent study shows that supermassive black holes are growing at rates that defy the limits of current theory. Astronomers just need to figure out how they’re doing it! 

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The Early Universe Had a Lot of Black Holes

The Hubble Ultra Deep Field seen in ultraviolet, visible, and infrared light. Image Credit: NASA, ESA, H. Teplitz and M. Rafelski (IPAC/Caltech), A. Koekemoer (STScI), R. Windhorst (Arizona State University), and Z. Levay (STScI)

The Hubble Deep Field and its successor, the Hubble Ultra-Deep Field, showed us how vast our Universe is and how it teems with galaxies of all shapes and sizes. They focused on tiny patches of the sky that appeared to be empty and revealed the presence of countless galaxies. Now, astronomers are using the Hubble Ultra-Deep Field and follow-up images to reveal the presence of a large number of supermassive black holes in the early Universe.

This is a shocking result because, according to theory, these massive objects shouldn’t have been so plentiful billions of years ago.

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Galaxies Regulate their Own Growth so they Don’t Run Out of Star Forming Gas

A simulation of a galaxy’s ‘heart and lungs’ at work is pictured inset on an artist's impression of bi-polar jets of gas originating from a supermassive black hole at the centre of a galaxy. Credit ESA/Hubble, L. Calçada (ESO) / C Richards/MD Smith/University of Kent Licence type Attribution (CC BY 4.0)

Look at most spiral or barred spiral galaxies and you will see multiple regions where stars are forming. These star forming regions are comprised of mostly hydrogen gas with a few other elements for good measure. The first galaxies in the Universe had huge supplies of this star forming gas. Left unchecked they could have burned through the gas quickly, generating enormous amounts of star formation. Life fast though and die young for such an energetic burst of star formation would soon fizzle out leaving behind dead and dying stars. In some way it seems, galaxies seem to regulate their star formation thanks to supermassive black holes at their centre. 

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Supermassive Black Holes Got Started From Massive Cosmic Seeds

The J0148 quasar circled in red. Two insets show, on top, the central black hole, and on bottom, the stellar emission from the host galaxy. Credit: NASA

Supermassive black holes are central to the dynamics and evolution of galaxies. They play a role in galactic formation, stellar production, and possibly even the clustering of dark matter. Almost every galaxy has a supermassive black hole, which can make up a small fraction of a galaxy’s mass in nearby galaxies. While we know a great deal about these gravitational monsters, one question that has lingered is just how supermassive black holes gained mass so quickly.

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Black Holes are Tearing Stars Apart All Around Us

Illustration of star remnants after it is shredded by a supermassive black hole. Credit: NASA

Galaxy NGC3799 lies around 16 million light years from Earth. Any event observed today within that galaxy took place 16 million years ago. One such event was observed in February 2023 when a surge in brightness in the core was followed by a rapid dimming. The observations that followed revealed that the event was a star being torn apart by a supermassive black hole at the heart of the galaxy. This is not the first time such an event has been observed but it is the first to be within our galactic backyard suggesting it may be more common that first thought. 

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