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---------------------------- - 2286 - Quasars - the hosts of super massive blackholes
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- These distant Quasars emitted their light 1 to 2 billion years after the Big Bang. Quasars appear different than stars because of the broad spectrum of their light. Their spectrum covers the full range from radio waves to X-rays.
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- The first Quasar was identified as 3C-273 in the Constellation Virgo. It was found as a radio source and later with a light spectrum of 13th magnitude. When the Doppler shift of the light was measured it was found to be 2 billion lightyears away yet with enough brightness to be seen by a backyard telescope. This meant its brightness had to be several hundred times brighter than the whole Milky Way Galaxy.
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- Quasar stands for Q.S.R.S., quasi-stellar radio source, because that is how they were first discovered. Today astronomers have cataloged over 13,000 Quasars. They expect the list to grow to over 100,000. Astronomers now believe that Quasars can be found at the center of every galaxy.
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- Some are more active than others. Some appear differently because of their orientation relative to our point of view. Their energy level is well beyond all the energy that a supernova or a neutron stars emits over its entire lifetime. They must be created by super massive blackholes at the center of these galaxies.
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- The best model astronomers have come up with for Quasars works like this: Gigantic Blackholes lie at the dense core of galaxies. Their immense gravity consumes all the matter that is around them. The matter in the form of gas and dust coming close to the blackhole orbit’s the horizon and flattens into a disk, called an accretion disk.
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- Collisions of atoms in this accretion disk heat up to very high energies. Their orbital velocities can approach the speed of light. Magnetic fields created by the rotating ionized atoms create magnetic poles that funnel the charged particles into twin jets exiting perpendicular to the disk.
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- We can calculate how big the Blackhole is that is consuming this mass if we know the velocity and the radius of the accretion disk. M87 is an active galaxy with gas rotating at 800 kilometers / second at a distance of 60 lightyears from the center. This velocity was determined by the Doppler Shift of light moving towards us (blue shifted) on one side of center and moving away from us (redshifted) on the opposite side of center.
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---------------- mass = radius ( velocity)^2 / Gravitational Constant
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---------------- m = r * v^2 / G
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---------------- m = 60*9.46*10^15 meters ( 8*10^5 m/sec)^2 / 6.67 * 10^-11 m^2/kg*sec^2
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---------------- m = 5.4*10^39 kilograms
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---------------- m = 2,700,000,000 Solar Mass
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- This model can be used to explain the wide bandwidth of radiation emitted by the Quasar. Nuclear fusion can convert mass-energy to photons with 1% efficiency. Depending on the rotation velocity of the accretion disks these Quasars can convert mass-energy to photons with 10% to 40% efficiency.
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- If rotating accretion disks can convert mass to energy with 10% to 40% efficiency, how much mass is consumed according to Mass = Energy / speed of light squared?
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------------------------------ E = mc^2
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------------------------------ At 10% efficiency m = 0.10*E / c^2.
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------------------------------ The measured luminosity of a Quasar is 10^40 watts.
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- A watt is a joule of energy per second, and a joule of energy = a kilogram / meter^2 / sec^2.
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----------------------------- m = 1.1*10^24 kilograms per second.
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----------------------------- There are 86,400 seconds in a day.
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----------------------------- There are 2*10^30 kilograms in the mass of the Sun.
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----------------------------- m = 4.75% the mass of the Sun every day.
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----------------------------- m = 17 Suns being consumed by the Quasar every year.
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- The wide bandwidths of the emitted radiation can come from many different processes. Hot gases above the accretion disk produce ultraviolet and X-rays. This radiation ionizing more interstellar gas produces visible light. Dust clouds absorb radiation and re-emit infrared light. High velocity electrons in the jet streams produce radio emissions.
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- The jets shoot far out to reach other interstellar gas. The jets are concentrated into narrow beams by twisted magnetic field lines. Charged particles are shot out of the rotating poles at high velocities in twirling strings along these field lines.
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- Ultimately all the energy comes from the gravitational energy of the mass of the blackhole. Gravitational energy is converted into Kinetic energy in the rotating accretion disk. Collisions between particles in the accretion disk converts kinetic energy into thermal energy. Thermal energy emits intense radiation that we observe in light waves.
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- The earliest Quasars, and earliest galaxies, were made from hydrogen gas. After billions of years of star formation in these galaxies many supernovae occurred spreading the heavier elements into the interstellar gas. Later galaxies that are not so distant contain many of these higher level elements. The birth of galaxies is still not well understood. But, the role of massive Blackholes must play a major part.
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- The Quasars were first discovered in 1963 by the Dutch astronomer Maarten Schmidt. Observing 3C273 from Palomar Observatory, California. He recognized the spectrum of hydrogen shifted to redder wavelengths. The redshift was 0.158 which meant the source must be 2 billion lightyears away. To be a 13th magnitude it must be 100 times brighter than a normal galaxy.
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- Then another quasar was soon found to have a redshift of 0.3679 corresponding to a distance of 4 billion lightyears away. In 1973 a paper was published concluding that all quasars were the nuclei of giant galaxies.
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- Many Quasars emit X-rays. Some even shine in infrared light as the rotating dust re-emit’s a longer wavelength. In 1969 Donald Lynden-Bell did the math to show that the gravitational potential energy around a blackhole with a mass of 10 billion Suns compressed into 10 light-hours diameter had the energy to explain the energy output of these quasars. The gravitational potential energy is converted into radiation across the entire spectrum.
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- It always pays to do the math.
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- February 26, 2019. 944
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--------------------- Tuesday, February 26, 2019 -------------------------
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