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Universe and Black Holes - Andrew Fabian. Astrophysics 🌚 Lecture for Sleep & Study

LECTURES FOR SLEEP & STUDY・2 minutes read

The text discusses the extreme power in the universe, highlighting solar flares, supernovae, neutron stars, and black holes, emphasizing their impact on the cosmos and galactic formations. It explores the formation, energy release, and implications of black holes, from their discovery to their role in galaxy evolution and potential for time travel through wormholes.

Insights

Solar flares can have significant impacts on Earth, causing auroras and disruptions to technology, emphasizing the potential dangers of solar flares to modern technology.
Supernovae lead to the creation of heavy elements like oxygen and iron, with most of the oxygen in our bodies originating from supernova explosions, highlighting their crucial role in the universe.
Black holes warp space-time, have an event horizon beyond which nothing can escape, and can be observed through X-ray images, showcasing their immense power and significance in astrophysics.
Black holes, through accretion of matter, release energy efficiently, with black hole feedback influencing galaxy formation and impacting star formation, illustrating their role in shaping the cosmos.

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Recent questions

What is a solar flare?
A sudden burst of energy from the Sun.
What is a neutron star?
A highly dense, compact stellar remnant.
What is a black hole?
A region of spacetime with intense gravitational pull.
What are gravitational waves?
Ripples in spacetime caused by massive objects.
What is the Eddington limit?
A restriction on the power of celestial objects.

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Summary

00:00

"Power and Dangers of Solar Flares"

The Big Bang is discussed as the origin of space and time, but the focus is on the extremes of power in the universe.
Solar prominences and eruptions from the Sun are highlighted, driven by gravity and magnetism.
Solar flares, like the one observed by Richard Carrington in 1859, can have significant impacts on Earth, causing auroras and disruptions to technology.
The potential dangers of solar flares to modern technology, such as satellites and transmission systems, are emphasized.
The frequency and energy of solar flares are plotted, showing the rare occurrence of super flares.
The maximum power that can be generated from an object is calculated using Einstein's equation, resulting in an astronomical figure of 3.6 x 10^52 Watts.
The Eddington limit is explained as a restriction on the power of objects due to radiation pressure, preventing them from blowing themselves apart.
A mass-radius plot is used to explain the life cycle of stars, from stable objects like white dwarfs to collapsing cores forming black holes.
The process of star death is detailed, with less massive stars becoming white dwarfs and more massive stars collapsing into black holes.
The significance of understanding exploding stars and the different types of celestial objects, like white dwarfs, neutron stars, and black holes, is underscored.

18:13

"Supernovae, Neutron Stars, and Black Holes"

A supernova explosion occurs when a star collapses, releasing an enormous amount of energy in minutes and seconds.
Medium-sized stars can collapse into neutron stars, throwing off mass in the process.
The only visible supernova explosion occurred in 1987 in the Large Magellanic Cloud, a satellite galaxy of our own.
Supernovae lead to the creation of heavy elements like oxygen and iron, with most of the oxygen in our bodies originating from supernova explosions.
Neutron stars, like the one from the 1054 AD supernova, are highly magnetized and spin rapidly, emitting flashes of radiation.
Pulsars, highly magnetized neutron stars, emit radiation across various wave bands and can cause Earth's atmosphere to ring like a bell.
Magnetars, neutron stars with extremely high magnetic fields, can crack and release intense flashes of radiation, like the one in 2004.
Black holes, like the one at the center of our galaxy, warp space-time and have an event horizon beyond which nothing can escape.
The concept of black holes originated in the 18th century, theorized by John Mitchell, suggesting that stars with enough mass could have an escape velocity greater than the speed of light.
Observations of stars orbiting the center of our galaxy indicate a compact object with a mass four million times that of the sun, likely a black hole due to its extreme density.

38:05

"Black Holes: Energy, Power, and Mysteries"

Einstein developed the general theory of relativity, leading to the concept of black holes.
Equations for black holes were solved by Carl Schwarzschild for a stationary Point Mass and by Roy Kerr for a spinning object in 1963.
Black holes can be observed through X-ray images, showing objects like white dwarfs, neutron stars, and active stars.
Material falling into black holes releases significant energy, making them visible through accretion.
Accretion disks around black holes generate powerful jets, producing immense power.
Nuclear fusion is a hundred million times more efficient than chemical reactions, powering the Sun.
Black holes at the center of galaxies control the mass and star formation of the entire galaxy.
Jets from black holes can lead to phenomena like quasars and gamma-ray bursts.
Fast radio bursts, discovered in 2007, remain a mystery with various theories about their origin.
Recent observations have revealed repeating fast radio bursts from a specific source, possibly a pulsar on steroids, ruling out cataclysmic sources.

57:04

"Black Holes, Gravitational Waves, and Cosmic Origins"

The Small Magellanic Cloud, originating from the Large Magellanic Cloud, has a mass similar to a tiny galaxy, with bursts that briefly outshine all other stars in the galaxy.
These bursts, occurring three billion light years away, likely happened three billion years ago, possibly due to young magnetars.
Another type of flare results from a star being torn apart by a black hole's tidal forces.
Binary stars spiraling together cause gravitational radiation, generating ripples in space-time.
Merging neutron stars can produce gamma-ray bursts and heavy elements like gold, explaining the origin of gold in the universe.
Gravitational wave detectors like LIGO can measure changes in length equivalent to the size of an atom versus the distance between the Earth and the Sun.
LIGO detected the merger of two 13 solar mass black holes, forming a 60 solar mass black hole, with three solar masses lost to gravitational radiation.
The power from this black hole merger exceeded the total power from all stars in all galaxies in the universe.
John Mitchell first introduced the concept of black holes in 1784, suggesting their existence based on gravitational influences on neighboring stars.
Albert Einstein's general theory of relativity explained how mass perturbs space-time, leading to the discovery of the bending of light by the Sun in 1919.

01:17:11

Exploring Black Holes: Mathematical and Observational Aspects

Black holes are a subject of extensive research, particularly focusing on the mathematical aspects related to the Event Horizon.
The discussion shifts to observing black holes as tangible objects in the universe, specifically astrophysical black holes.
A comparison is made between the formation of a black hole and the concept of a canoe approaching Niagara Falls, emphasizing the point of no return at the Event Horizon.
The frequency of light and the color of objects change as they approach a black hole due to the warping of space and time.
Gravitational redshift, affecting the frequency of light, is a phenomenon present around any mass, including Earth, impacting GPS satellites.
Astrophysical black holes are categorized based on mass and spin, with The Event Horizon typically being three kilometers per solar mass.
The known astrophysical black holes fall into two main categories: Stellar Mass (3-150 solar masses) and Supermassive (100,000-10 billion solar masses).
The center of the Milky Way galaxy is home to a well-studied black hole, with astronomers using adaptive optics to observe its surroundings.
The Nobel Prize in Physics was awarded for research on the black hole at the center of the Milky Way, showcasing the orbits of stars around it.
Various galaxies, including M87 in the Virgo cluster, have been studied to confirm the presence of black holes at their centers, with some exhibiting active behavior like quasars.

01:35:18

"Quasars, Black Holes, and Galactic Energy"

Quasars are incredibly luminous and distant, ten times more luminous and voluminous than galaxies, with the first one discovered being 3C273 in 1963 by Martin Schmidt.
3C273, part of the third Cambridge catalog of radio sources, is a radio source with a jet of material squirted out at high velocities, believed to originate from a massive black hole.
Quasars like 3C273 vary in brightness over short periods, indicating a small size, possibly smaller than the solar system, yet producing immense power, suggesting a massive black hole at their core.
X-rays, more energetic than visible light, come from objects thousands to tens of millions of degrees hotter than stars, such as binary stars and neutron stars like the Trap Nebula.
Accreting black holes, like those studied through X-ray astronomy, have material swirling around them in discs, releasing vast amounts of energy due to friction and magnetic fields in a region called the Corona.
By studying the emission from accreting black holes, particularly the iron line spectrum, researchers can determine the black hole's spin and proximity to the black hole.
Black holes, through accretion of matter, release energy efficiently, with black hole accretion being 0.1 mc², significantly more than nuclear fusion, making it a potent energy source.
Black holes, growing up to a billion solar masses through accretion, release energy that can affect galaxies, with the energy release to grow a black hole being over a hundred times the binding energy of a galaxy.
Black hole feedback, where energy from black holes affects the gas in galaxies, can influence galaxy formation, with active galactic nuclei blowing gas out of galaxies, impacting star formation.
Radiation pressure, demonstrated by the tails of comets like Hale-Bopp, showcases how energy from stars can push dust and ions away, affecting the dynamics of celestial bodies and phenomena.

01:53:29

"Active Galaxies Shape Stars with Energy"

Active galaxies exhibit star formation due to energy from jets and winds pushing gas out.
Energy from active galaxies changes the potential for star formation and shapes the galaxy.
Chandra Observatory image of the Perseus cluster shows bubbles caused by energy from the active nucleus.
The size ratio between the Event Horizon of a black hole and the active galaxy's region is about a billion.
Gravitational waves were first predicted by Einstein in 1916 and discovered in 2015 by LIGO.
Maximum power from mass is calculated as 4 x 10^52 Watts, with the maximum power in the universe being 10^26 solar luminosities.
Gravitational waves travel at the speed of light and are not affected by different mediums.
Hawking radiation from black holes is minimal for astrophysical black holes.
Gravity warps space and time, affecting how matter behaves.
Merging black holes can result in a recoil effect, ejecting the resulting black hole from the galaxy.

02:12:37

"Black Holes, Time Travel, and Galaxies"

Time travel is theoretically possible through wormholes in spinning black holes, leading to potential travel to other universes.
The spiral shape of the Milky Way is caused by interactions within stars and self-gravity of material in the disc, originating from tidal interactions in the early universe.
Supermassive black holes are located at the center of galaxies due to their massive size perturbing star fields and transferring energy to stars, causing them to fall into the center.
Multiple black holes can exist in a galaxy, with the potential for mergers that can be measured through instruments like LIGO and future space missions like Lisa by the European Space Agency.

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