Tuesday, May 2, 2023

3983 - QUASAR - largest found.

 

-   3983  -  QUASAR  -  largest found.     Quasars, the most extreme phenomena in the universe, are triggered when galactic collisions deliver gas to feeding black holes.


------------------------------  3983  - QUASAR  -  largest found.

-   Scientists may have solved a 60-year-old mystery by discovering that “quasars”, energetic objects that are powered by supermassive black holes and outshine trillions of stars combined, form when galaxies collide and merge.

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-    The Milky Way could host a quasar of its own when it collides with the neighboring Andromeda galaxy several billion years from now.

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-   Scientists have previously tracked quasars' bright, energetic emissions to regions at the hearts of galaxies that span roughly the width of the solar system, meaning quasars must come from incredibly compact objects.

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-    The leading theory suggests that quasars are supermassive black holes heating huge amounts of surrounding gas, thus releasing tremendous amounts of radiation before the material falls onto the black hole's surface.

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-    Since their discovery sixty years ago, quasars have puzzled scientists, mainly because it's unclear just how supermassive black holes can draw in enough raw material to fuel such powerful emissions. While supermassive black holes dwell at the centers of most galaxies, the gas needed to fuel quasars tends to orbit on the outskirts of galaxies. Thus, there must be some delivery service moving gas toward the hearts of galaxies.

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-   Deep imaging observations from the “Isaac Newton Telescope” in Spain's Canary Islands to finally solve this puzzle.  To understand how quasars are ignited we need to determine how gas can fall into the center of the host galaxies at sufficiently high rates.

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-    One idea is that the necessary radial infall is caused by collisions between galaxies, whose associated gravitational forces can perturb the gas from its usual circular orbits.

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-    When comparing  48 nearby galaxies hosting quasars to 100 non-quasar galaxies, the researchers discovered the presence of distorted structures at the edges of the quasar-hosting galaxies. These structures also indicate a past or ongoing collision and merger with another galaxy.

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-    Astronomers found a high rate of such structures in quasar-hosting galaxies, three times that measured for a carefully matched control sample of non-quasar galaxies that were imaged with the same techniques.   This provides strong evidence that quasars are triggered in galaxy collisions.

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-    Quasars can have a large influence on the evolution of galaxies that host them; better understanding how quasars ignite could help scientists hone their models of galaxy evolution and the evolution of the universe as a whole.

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-    It's important to understand how, when, and where quasars are triggered, as once triggered, the enormous radiative power generated by a quasar can have a major, damaging effect on the surrounding host galaxy.

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-    The pressure of the radiation can expel the remaining gas in the remnant galaxy system. Since gas is required to form new stars, this will cut off any future star formation activity, effectively the death throes of the galaxy.

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-     The nearest large galaxy,  the “Andromeda Spiral”,  is coming directly towards us at a high velocity, and will collide and merge with the Milky Way in around 5 billion years.  When this happens, it's likely that a quasar will be triggered as gas falls into the center of the remnant system.

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-     Black holes like these, known as quasars, are the biggest types of black holes we know about.   Black holes are some of the most massive single objects in space, but what's the biggest one in existence, and how big can they get?

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-    There is a theoretical limit to the size of black holes, celestial  objects so massive that even light cannot escape them. And the largest directly observed black hole with a confirmed mass is right around this limit.

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-    This monster, named “TON 618”, weighs roughly 40 billion solar masses. TON 618 has a radius of over 1,000 astronomical units (AU), which means that if the black hole was placed in the center of the solar system, by the time you reached Pluto, you would  be less than 5% of the way from the center of the black hole to its edge.

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-   TON 618 sits about 18.2 billion light-years away from Earth. In the night sky, it sits  on the border between the constellations Canes Venatici and Coma Berenices. Astronomers first spotted it in a 1957.   They first thought it was a faint blue star, but observations a decade later revealed that the astronomers had glimpsed intense radiation from the material falling into the giant black hole.

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-    TON 618 powers a quasar, one of the brightest objects in the entire universe with the illuminating power of 140 trillion suns. Quasars draw light from the gravitational energy of the central black hole. Material around the black hole falls in, and as it does so it compresses and heats up, releasing enormous amounts of radiation.

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-     While individual events like the most powerful supernovas can briefly outshine quasars, they only last a few weeks. In contrast, quasars can shine for millions of years.   However, quasars are so far away that they only appear as faint spots of visible light in even the most powerful telescopes, and astronomers first detected them by their powerful radio emissions.

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-    Supermassive black holes become enormous through a combination of merging with other black holes and by constantly feeding on surrounding material.

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-    The  feeding rate is what sets the limit on the size of a black hole. These cosmic vacuum cleaners can only consume so much material in a given amount of time. As material falls in, it heats up and releases radiation (creating a quasar), but that radiation heats the material itself, preventing it from quickly falling into the black hole.

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-    This self-regulation prevents black holes from growing too quickly. Astronomers can estimate a maximum mass for a black hole by taking that feeding rate and multiplying it by the known age of the universe, giving an estimated maximum mass of around 50 billion solar masses.

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-   That is only an estimate. There may be other, more exotic, ways to create large black holes, such as from the direct collapse of large clumps of dark matter in the early universe. So,  it's still possible that there are even more massive black holes out there.

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                   April 30, 2023                 QUASAR  -  largest found.            3983                                                                                                                          

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