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-------------------- 2506 - QUASARS - extreme blackholes
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- Galaxy Blackholes at a Distance. Seeing galaxies at a distance requires seeing in the far infrared light. The expansion of space over cosmic distances stretches the wavelengths of visible light making the light redder and redder until is in the infrared part of the spectrum.
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- Quasars are the brightest objects in the Universe. They are the result of active accretion disks orbiting Blackholes that are at the centers of distant galaxies.
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- One of the first Quasars studied in 1963 , 3C273, had the wavelength of light shifted 16% which meant the galaxy was 2 billion lightyears away. In 1963 it was the farthest Quasar discovered. Today, it is the nearest known Quasar. There are many Blackholes in the centers of galaxies that are closer, but, they are not active, or bright enough to be called Quasars.
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- Most Blackholes at the centers of galaxies are “ sleeping”, not actively consuming material from their orbiting accretion disks. Active Blackholes are mammoth, billions of Solar Mass, at the center of galaxies having spinning accretion disks of gas and dust.
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- The rings of material at the edge of the Event Horizon, closest to the Blackhole, are orbiting faster than the outer rings. This causes friction between the fast moving and slow moving material.
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- This friction increases temperatures causing the material to radiate in the ultraviolet. Electrons are stripped from their atoms, then slam into gas atoms emitting X-rays. Rotating plasma, the rotation of charged particles, create spinning magnetic field lines that launch material in jets at the poles, perpendicular to the rotating disk.
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- The jets that are launched out the poles slam into galactic gas that generates radio waves. Active Blackholes create so much radiation because gas atoms are loosing and recapturing electrons. Going from charged particles to neutral particles.
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- When electrons are captured by a shell of a particular atom they emit a specific energy level, which is the same as a specific wavelength of electromagnetic radiation. For example, when hydrogen captures an electron it emits a defined 656 nanometers wavelength, a deep red in color. Each element will emit a defined wavelength spectrum for its particular shell energy levels.
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- Astronomers can identify this hydrogen element ( 656.3 nanometers) at different parts of the rotating accretion disk. Because emissions moving away from us are shifted to slightly longer wavelengths and emissions moving towards us to slightly shorter wavelengths astronomers can measure the velocity of the accretion disk rotation.
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- Knowing the speed of rotation they can determine the time and distance of one complete revolution. Knowing the period of orbit astronomers can measure the mass to the Blackhole at the center.
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- The heaviest Blackhole ( NGC 1277) was measured to be 17 billion Solar Mass. This is 4,000 times bigger than the Blackhole at the center of the Milky Way Galaxy. Our much smaller Blackhole is sleeping, not active.
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- Currently, over 228,468 Quasars have been cataloged all over 1 billion years old. Of these, about 5% are active today. Today, of course, is looking backwards in time to a few billion years after the Big Bang. Cosmic history reveals that there were many more active Blackholes in the early Universe then there are today.
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- The distant Quasars and distant supernovae are measured by their brightness and by their amount of “ redshift”. Redshift is defined as the ratio of the amount of wavelength shift to the original source wavelength.
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-------------------- redshift = z = wo - ws / ws
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--------------------- wo - wavelength of the shifted light that is observed.
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-------------------- ws = wavelength of the emitted light at the source.
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------------------- z = wo/ws - 1
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- If the original wavelength, ws, was emitted from the source at 500 nanometers. And, the amount of shift that was observed ( wo - ws ) was 2000 nanometers, then:
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------------------------z = 2000 / 500 - 1
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----------------------- z = 3
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- A redshift of 3 is when the Universe was about 400,000 years old, called the
Re-ionizaton Period. This occurred after the Cosmic Microwave Background radiation was released. The CMB radiation was shifted into the microwave spectrum, wavelengths longer than the infrared. Re-ionization occurred later because the photons of this earlier emission slammed into gas atoms causing them to loose electrons and become ionized.
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- The Webb Space Telescope can detect infrared spectrum out to 25,000 nanometers wavelength. That corresponds to a redshift, z = 49.
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------------------------z = 25,000 / 500 - 1
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----------------------- z = 49
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- A supernova of a star that is 150 Solar Mass would have a brightness Magnitude of +29 occurring 1 million years after the Big Bang. That is about the limit of the Webb Telescope camera using a 10,000 second exposure. The redshift in this case would correspond to about z = 25.
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- The more positive the Magnitude the dimmer the brightness. The faintest star visible to the naked eye is +6. Each Magnitude step represents a factor of 2.512 brightness change, so, 5 Magnitudes is a factor of 100 . ( 5^2.512) = 100.
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- A Magnitude difference of 23 ( 29 - 6 ) is ( 2.512^23) = The Webb telescope can see 1.6 trillion times dimmer than the naked eye can see. The brightest objects in the Universe at the farther distances allow us to see backwards in time.
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- Seeing with the far-infrared telescopes is like having a time machine.
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- November 29, 2019 2506 1591
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--------------------- Friday, November 29, 2019 --------------------
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