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So far! The most distant quasars: active galaxies with supermassive black holes as nuclei

by Aliser 2 months ago in Science
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The most distant quasars

Astronomers have discovered the most distant quasar to date, and like other quasars observed at this distance, it also presents a "huge" problem: the active galactic nucleus' energy-feeding black hole is far too large for the space-time it exists.

This quasar is named J031343.84-180636.4 (hereafter J0313) according to its position in cosmic space. It is one of the objects discovered through Pan-STARRS observations. The Pan-STARRS program, known as the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), uses a 1.8m telescope to collect images deep in the stars and obtain accurate information about the colors of the objects through different filters. Ultra-far quasars behave brightly in the red light range while emitting less light in the blue wavelength range, a property that makes them easier to detect in the collected images of the cluster.

When J0313 was discovered, spectral analysis with the larger Magellan and Gemini telescopes confirmed its infinite distance from Earth: the light we receive from this quasar travels at least 13 billion years, meaning that we are looking at a view 670 million years after the Big Bang.

Illustration: Quasar J0313-1806 is the most distant quasar ever discovered. It is 1000 times brighter than the entire Milky Way galaxy and a hundred trillion times brighter than our Sun. The diagram shows the composition of the nucleus and surrounding material of the active quasar system. The nucleus is a supermassive black hole, 1.6 billion times the mass of the Sun. The central body is surrounded by a hot accretion disk of diffuse matter emitting electromagnetic energy. The wind flow at the periphery of the accretion disk is slow, only 20% of the normal speed of light. Its nearby host galaxy undergoes violent new birth and remodeling, 200 times faster than the rate of newborn stars in the Milky Way.

Quasars are a class of active galaxies. Each massive galaxy has a supermassive black hole at its core, some of which are still actively consuming the surrounding gas, dust, and stars. These form huge, hot accretion disks around them, emitting a glow so intense that it dwarfs even the entire remaining galaxy.

To make the matter more compact (compressed density), the magnetic field of the accretion disk forms a tornado-like twin vortex that pulls matter close to the black hole and then bursts into jets. When these jets happen to point roughly at our space, we observe the galaxy to be extra bright. These star-like objects are called quasars.

Considering that we observed J0313 remaining so bright at such a distant distance, astronomers measured its total luminosity - a hint of how much energy it emits - to be 36 trillion times that of the Sun.

This is just too .... Dazzling! A full 3,000 times brighter than our Milky Way!

So what's going on with the super-sized black hole that's feeding all this energy? A deep-spectrum shot of J0313 by the Magellan Telescope sheds further light on the mass of this black hole. A portion of the matter spinning around the accretion disk is escaping around, so (according to the Doppler effect) the spectrum of light from the quasar shifts toward the red spectrum, while the portion spreading toward us is blueshifted. This color trailing effect shows the total amount that can be used to determine the mass of the black hole, and the scientists obtained a shocking result: this black hole has 1.6 billion times the mass of the Sun.

We know of many black holes with similar masses, some even larger, but all have experienced billions of years to expand to that size. The limit of what is known is the black hole of the J0313 quasar, which is as young as 670 million years, but how did it expand quickly to that scale?

This is a question that is still being explored in cosmology. We have seen other quasars at about this distance that also have massive black holes that are much larger than we can perceive growing as much as possible in a finite time (for the length of the galaxy's existence).

The problem is that there is a limit to how fast a black hole can swallow objects. The matter first forms a disk around it, and this accretion disk is so energetic and extremely hot that it emits radiation that hits objects falling toward the black hole and then ejects them into the surrounding area. The rate at which a black hole of a given mass swallows an object is balanced by the radiation it emits, a property known as the Eddington limit. If a black hole absorbs too fast, it "kills itself" and loses its "food source".

This means that it is very difficult to quickly become a black hole more than a billion times the mass of the Sun, but astronomers have tried to come up with some explainable theories. Perhaps a smaller black hole (a hundred or a thousand times the mass of the Sun) - a seed black hole - that grows and fuses rapidly at the beginning of a galaxy's nascent life offers some possibility for this phenomenon, but after that, it still requires the black hole to keep expanding extremely fast.

However, exactly how this process works is not known. We have very little information about quasars at this distance (the universe is vast, we have never probed this far, and it is not easy to detect them from dense images of the stars), but based on our limited knowledge, these quasars all have massive black holes growing as nuclei. It is worth noting that we do not deny the existence of less massive and less energetic quasars in unknown space, but at the same time, they are dimmer and therefore harder to find. Even if we find them and prove that low-mass black holes can form, the reason for the formation of the "giant" at hand is still a mystery.

The galaxies surrounding this black hole are bursting with new stars at a rate several hundred times that of the Milky Way, and we call such galaxies starburst galaxies. This phenomenon makes sense with a massive black hole, surrounded by enough material to form planets while filling the central nucleus with a "gobbling monster".

It is important to understand all this. First, we know that galaxies and black holes grow together, so understanding one means we can understand the other. At the same time, this can give us important hints about what everything looked like at the time of the cosmic divide. In addition, the light emitted from these distances passing through objects to reach Earth can also give us some insight into how matter between these not-so-distant universes influences the behavior of light.

Now that we know that J0313 is there, it will be used as the main target of a series of follow-up studies that will allow people to try to crack more secrets about its existence. These quasars reveal questions whose answers will eventually emerge as we learn more about them.


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