Super Massive Black HolesSuper Massive Black Holes

A Talk Given By:A Talk Given By:

Mike EwersMike Ewers

Black Holes: A Theoretical Black Holes: A Theoretical Definition (A Review)Definition (A Review)

An area of space-time An area of space-time with a gravitational with a gravitational field so intense that field so intense that its escape velocity is its escape velocity is equal to or exceeds equal to or exceeds the speed of light. the speed of light.

The Important thing is The Important thing is that this area can be that this area can be of any size.of any size.

The Finite Speed of LightThe Finite Speed of Light

As you all know As you all know (especially (especially Contemporary Contemporary people), That the people), That the speed of light is a speed of light is a finite value in a finite value in a vacuum.vacuum.

(A black-hole-powered jet of sub-atomic (A black-hole-powered jet of sub-atomic particles traveling at nearly the speed particles traveling at nearly the speed of light out of the M87 galaxy) of light out of the M87 galaxy)

Escape Velocity, Density, and Escape Velocity, Density, and Schwarzschild RadiusSchwarzschild Radius

In terms of In terms of gravitational force, gravitational force, every object has an every object has an escape velocity as escape velocity as

vvescesc = = SqrtSqrt[[(2 G M)/r(2 G M)/r]. ]. From that From that

Schwarzschild Radius Schwarzschild Radius can be easily found.can be easily found.

All comes down to a All comes down to a matter of density.matter of density.

Thinking in Terms of General Thinking in Terms of General RelativityRelativity

Einstein’s Theory of Einstein’s Theory of General Relativity General Relativity basically says that basically says that gravity warps space gravity warps space time.time.

Rubber Sheet Rubber Sheet analogueanalogue

Down, up, and through the funnel. An Down, up, and through the funnel. An embedding diagram is generally a good embedding diagram is generally a good representation of a black hole's warping of representation of a black hole's warping of nearby space-time. But such 2-dimensional nearby space-time. But such 2-dimensional illustrations can also cause conceptual illustrations can also cause conceptual problems. problems.

This is a simplified modelThis is a simplified model

The black hole no hair The black hole no hair theorem shows that theorem shows that mass, charge, and mass, charge, and angular momentum angular momentum are the only are the only properties a black properties a black hole can possess hole can possess

Types of Black HolesTypes of Black Holes

““Normal Sized” Black Normal Sized” Black HolesHoles

Microscopic (Primordial) Microscopic (Primordial) SizedSized

Super-Massive Black Super-Massive Black Holes (On the order of Holes (On the order of millions to billions of Solar millions to billions of Solar Masses)Masses)

(Estimated 3 million solar (Estimated 3 million solar masses for Milky Way masses for Milky Way Black Hole)Black Hole)

How Normal Black Holes Come How Normal Black Holes Come About (A Review)About (A Review)

Most Black Holes are Most Black Holes are believed to come believed to come about from the death about from the death of massive stars.of massive stars.

Stellar Evolution (Brief)Stellar Evolution (Brief)

Star (Mass of Hydrogen) is massive Star (Mass of Hydrogen) is massive enough (M > 0.1 Menough (M > 0.1 Msunsun ) to ignite fusion ) to ignite fusion

Star performs stable core fusion (first Star performs stable core fusion (first H->HE) H->HE)

Cycle repeats if star is big enough until the Cycle repeats if star is big enough until the core is Fe.core is Fe.

Star is in a kind of onion peel structure of Star is in a kind of onion peel structure of elemental layerselemental layers

Supernovas!?Supernovas!?

After fusion cycles through and star’s core After fusion cycles through and star’s core is Fe, if the star now is M < 1.4 Mis Fe, if the star now is M < 1.4 Msun sun , the , the star will supernova as a Type II star will supernova as a Type II supernova. Otherwise, it becomes a white supernova. Otherwise, it becomes a white dwarf, supported by degenerate electron dwarf, supported by degenerate electron pressure.pressure.

This mass limit for supernovas is the This mass limit for supernovas is the Chandrasekhar limit.Chandrasekhar limit.

Black Hole or Neutron Star?Black Hole or Neutron Star? If the star the went If the star the went

supernova was between supernova was between 1.4 and 3 M1.4 and 3 Msun sun , then the , then the remnant will be a Neutron remnant will be a Neutron Star supported by Star supported by degenerate neutron degenerate neutron pressure (Pulsar).pressure (Pulsar).

Otherwise, Otherwise, MMfinal final > 3M> 3Msun sun , and the , and the result is a black hole result is a black hole because the is no source because the is no source of outward pressure of outward pressure strong enough.strong enough.

Where Could Super-Massive Black Where Could Super-Massive Black Holes Exist?Holes Exist?

The only known The only known places in the Universe places in the Universe where there could be where there could be enough mass in one enough mass in one area is in the center area is in the center of massive galaxiesof massive galaxies

Not believed to be Not believed to be anywhere elseanywhere else

Quasars: What are They?Quasars: What are They? In some places where point sources of radio In some places where point sources of radio

waves were found, no visible source other than waves were found, no visible source other than a stellar-looking object was found (it looked like a stellar-looking object was found (it looked like a point of like --- like a star does). These objects a point of like --- like a star does). These objects were called the "qausi-stellar radio sources", or were called the "qausi-stellar radio sources", or "quasars" for short."quasars" for short.

Later, it was found these sources could not be Later, it was found these sources could not be stars in our galaxy, but must be very far away --- stars in our galaxy, but must be very far away --- as far as any of the distant galaxies seen. We as far as any of the distant galaxies seen. We now think these objects are the very bright now think these objects are the very bright centers of some distant galaxies, where some centers of some distant galaxies, where some sort of energetic action is occurring.sort of energetic action is occurring.

Active Galactic NucleiActive Galactic Nuclei In some galaxies, known In some galaxies, known

as "active galactic nuclei" as "active galactic nuclei" (AGN), the nucleus (or (AGN), the nucleus (or central core) produces central core) produces more radiation than the more radiation than the entire rest of the galaxy! entire rest of the galaxy! Quasars are very distant Quasars are very distant AGN - the most distant AGN - the most distant quasars mark an epoch quasars mark an epoch when the universe was when the universe was less than a billion years less than a billion years old and a sixth of its old and a sixth of its current size. current size.

Brief Review of case for Super-Massive Brief Review of case for Super-Massive Black Holes in these observed AGNBlack Holes in these observed AGN

The Time Variation of The Time Variation of AGNAGN

The Eddington The Eddington Luminosity ArgumentLuminosity Argument

The Motion of broad The Motion of broad line emission medium line emission medium around the central around the central corecore

How did Super-Massive Black How did Super-Massive Black Holes come about?--theoriesHoles come about?--theories

From “Lumps” in the From “Lumps” in the early universeearly universe

The “Stellar Seed” The “Stellar Seed” ModelModel

Collapse of a whole Collapse of a whole star clusterstar cluster

Lumps from the early UniverseLumps from the early Universe In the “Big Bang” the In the “Big Bang” the

whole universe was in a whole universe was in a really dense state. So really dense state. So much that perhaps lumps much that perhaps lumps could have formed and of could have formed and of matter dense enough that matter dense enough that a black hole was formed.a black hole was formed.

There was enough There was enough surrounding matter that surrounding matter that galaxies formed around galaxies formed around the lumpsthe lumps

Could explain why Could explain why pockets of interstellar gas pockets of interstellar gas never became galaxiesnever became galaxies

The Stellar Seed ModelThe Stellar Seed Model

Provided that the Provided that the surrounding surrounding environment is environment is sufficiently rich in sufficiently rich in matter, a giant black matter, a giant black hole could result in an hole could result in an initial “stellar seed” of initial “stellar seed” of 10 M10 Msun sun produced produced during a supernova.during a supernova.

Collapse of a whole clusterCollapse of a whole cluster If the stars of a tight knit If the stars of a tight knit

cluster of the moderately cluster of the moderately young Universe had all young Universe had all relatively the same size relatively the same size stars (above the stars (above the Chandrasekhar Limit), Chandrasekhar Limit), there would be quite a there would be quite a few Black Holes forming few Black Holes forming simultaneously causing simultaneously causing smaller stars to be smaller stars to be absorbed, and black absorbed, and black holes to combine.holes to combine.

NGC 1850 to the rightNGC 1850 to the right

Some Characteristic of AGNSome Characteristic of AGN

Super Bright: AGN Super Bright: AGN 3C273 (an extreme 3C273 (an extreme example) is L = example) is L = 4.8*10^12 L4.8*10^12 Lsun sun ..

Cosmic Optical JetsCosmic Optical Jets Tidal forcesTidal forces Cannibalism—they do Cannibalism—they do

eat, the source of eat, the source of energyenergy

Optical Jets—Why?Optical Jets—Why? The magnetic fields around The magnetic fields around

a black holes that are a black holes that are thought to produce the thought to produce the spectacular jets of high-spectacular jets of high-energy particles rushing energy particles rushing away from black holes away from black holes come from the disk of hot come from the disk of hot gas around the black hole, gas around the black hole, not the black hole itself. not the black hole itself.

The jets are made by the The jets are made by the Magnetic field of the matter Magnetic field of the matter before it goes in the Black before it goes in the Black Hole.Hole.

Emit Synchrotron radio Emit Synchrotron radio signalssignals

Cygnus A Cygnus A

Tidal forces stretch farther, but are Tidal forces stretch farther, but are weakerweaker

The tidal force is proportional to the The tidal force is proportional to the mass of the black hole. In other words, mass of the black hole. In other words, as the object gets more massive, the as the object gets more massive, the force should get bigger too. But the force should get bigger too. But the force is also force is also inverselyinversely proportional to proportional to the the cube of the object's radiuscube of the object's radius. As the . As the hole gets more massive, its size hole gets more massive, its size increases, but because of the cube increases, but because of the cube factor, the force factor, the force decreasesdecreases much much faster than any possible mass increase faster than any possible mass increase can account for. The result is that big can account for. The result is that big black holes have weak tidal forces, black holes have weak tidal forces, and small ones have strong tidal and small ones have strong tidal forces.forces.

Frames from a NASA computer Frames from a NASA computer animation depict one possible cause of animation depict one possible cause of gamma ray bursts. A star orbiting a gamma ray bursts. A star orbiting a black hole spirals in as it is shredded black hole spirals in as it is shredded by tidal forces, generating an intense by tidal forces, generating an intense burst of gamma and other radiation as burst of gamma and other radiation as the its matter is compressed and the its matter is compressed and super-heated on its way to oblivion. super-heated on its way to oblivion.

CannibalismCannibalism Apparently, Quasars are Apparently, Quasars are

only active on order of only active on order of 100 million years100 million years

A dead quasar could be A dead quasar could be revived with a new source revived with a new source food—by colliding food—by colliding galaxiesgalaxies

Proof—elliptical galaxies Proof—elliptical galaxies have been found to be have been found to be active in radio active in radio transmissions as well.transmissions as well.

Collision Galaxies NGC 2207 & IC 2163Collision Galaxies NGC 2207 & IC 2163

Observations of Super Massive Observations of Super Massive Black HolesBlack Holes

Radio observations at Radio observations at various radio various radio telescopestelescopes

X-ray observations X-ray observations from the orbital from the orbital Chandra ObservatoryChandra Observatory

Optical Observations Optical Observations from Hubble Space from Hubble Space TelescopeTelescope

PicturesPictures

NGC4261

Fate of Universe?Fate of Universe?

All Black Holes Evaporate over time due to All Black Holes Evaporate over time due to Hawking RadiationHawking Radiation

Eventually the Universe will have no Eventually the Universe will have no matter in a cold dark death and all there matter in a cold dark death and all there will be left is radiation.will be left is radiation.

Evaporation Time:Evaporation Time:

1 * 10^-7 (M/M1 * 10^-7 (M/Msunsun)^3 Years )^3 Years

On order of 1* 10^20 yearsOn order of 1* 10^20 years

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