PHYS 182 Lecture Notes - Lecture 17: Radio Wave, Weakly Interacting Massive Particles, Spiral Galaxy

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8 Jun 2018
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PHYS182: Our Evolving Universe
2017-11-07 LEC 17
Black Holes
- If you enter a small black hole, you get torn apart after the horizon. But if you enter a big black
hole, you don’t get torn apart at first but you will once you hit the singularity inside
o Science fiction: If you resolve the singularity you will get a new universe. This is
potentially how the big bang originated – from the singularity of a black hole. Within that
universe, there is a black hole that leads to another universe, and so on.
§ “Matrioshka universe”
Types of black holes
- Stellar mass black holes: ~10 or 20 solar masses
o CYGNUS X1 is the best example of a stellar black
hole. It is a binary with a star and some very
massive object (black hole) that is eating up the
mass surrounding it.
§ The mass falling into the black hole is
accelerating and radiating, therefore the
black hole is lit up and we can see it.
§ This is a candidate for a stellar mass black
hole.
§ Due to the magnetic fields of the black
hole, some of the material being sucked in
jets out at the poles
o LIGUS event: shows 2 black holes orbiting one
another.
§ The mass is accelerating and producing
gravitational waves. Eventually the horizons meet and they form one large black
hole.
§ Signal predicted is intensity as a function of time. There is a small amplitude and
the frequency is lower at the beginning, but then the frequency and amplitude
increases until the merge, and then there is a spin-down.
§ This is the best evidence of stellar mass black holes.
o What have we learned?
§ First direct evidence of gravitational waves
§ Best evidence for the existence of a black hole horizon
§ Best test of General Relativity close to a black hole horizon
§ First detection of a black hole binary system
§ Now we know the rate of black hole binaries
- Super-massive black hole
o Supermassive > 106 solar masses
o Each galaxy harbors in its center a super-massive black hole
o In the Milky Way: Follow positions of stars in the sky over a
long period of time, and oyu can compute the mass in a
particular region. The mass is 4x106 solar masses. But there is
nowhere near 106 stars visible, so it was assumed there was a
black hole.
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Document Summary

If you enter a small black hole, you get torn apart after the horizon. But if you enter a big black hole, you don"t get torn apart at first but you will once you hit the singularity inside: science fiction: if you resolve the singularity you will get a new universe. This is potentially how the big bang originated from the singularity of a black hole. Within that universe, there is a black hole that leads to another universe, and so on. Stellar mass black holes: ~10 or 20 solar masses: cygnus x1 is the best example of a stellar black hole. It is a binary with a star and some very massive object (black hole) that is eating up the mass surrounding it. The mass falling into the black hole is accelerating and radiating, therefore the black hole is lit up and we can see it. This is a candidate for a stellar mass black hole.

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