BLACK HOLE

Yingzhe HongPic:107CINE

First suggested in 1783 by John Michelle

First demonstrated by Albert Einstein in 1916 with his general theory of relativity

American astronomer John Wheeler applied the term “Black Hole” in 1967

A place in space where gravity is so extreme that nothing, even light could not escape from it

Invisible, the center of the black hole has infinite density

First black hole was discovered in 1971

Nuclear Fusion of Stars

Fusion of hydrogen to form helium

Mass also increases

Iron is too stable to release enough energy in fusion

Star dies

Gravitational Collapse

When a star runs out of “fuel”, it creates insufficient internal pressure to resist its own gravity

Temperature is not high enough

Pic：sandbh

lithium

Tolman-Oppenheimer-Volkoff Limit (TOV Limit)—Mass Limit of Neutron Star

Solar Masses (Mo)

White Dwarf: <1.5 Mo

Neutron Star: 1.5-3.0 Mo

Black Hole: >3.0 Mo

Schwarzschild Radius (Gravitational Radius): the radius of a sphere such that, if all the mass of an object were to be compressed within that sphere, the escape velocity from the surface of the sphere would equal to the speed of light. If the sphere collapses below the radius, light could not escape, so that black hole forms.

Staller black hole: formed by the collapse of a single star (>3Mo)

Intermediate-mass black hole(IMBH): merging of stellar black holes (100-1million Mo)

Supermassive black hole: located at the center of galaxies (up to billions Mo)

Singularity: the center of a black hole, has infinite density and gravitational force

Pic: Astronomy Source

Event Horizon: a boundary in spacetime beyond which events cannot affect an outside observer.

Pic: Wikipedia Commons

Observe stars, planets, and gas orbiting black holes

Look for vast amount of electromagnetic radiation (mainly X-rays) source Accretion of matter: matter fall further inward, releasing potential energy and increasing

temperature of gas.

When accreting object is a neutron star or a black hole, it emits large amount of electromagnetic radiation

The first discovered black hole: Cygnus X-1

Discovered in 1971

Stephen Hawking made a wager with Kip Thorne in 1975, with Hawking betting it was not a black hole.

Later discovery indirectly proved the existence of singularity

Hawking conceded the bet in 1990

Pic: 107CINE

Hawking Radiation: predicted to be released by black holes, reduces the mass and energy of black holes (black hole evaporation)

Gray Hole (Q-star): new definition for black hole, different from classic theoretical black holes that only “consume” matters

Related news: Supermassive black holes cause galactic-scale warming

New class of galaxies called “red geysers”, or dormant galaxies, where temperature is too high to form new stars

Star = gas + gravity, why not? Temperature due to “supermassive black hole wind”

Event Horizon Telescope (EHT): an international collaboration aiming to capture the first image of a black hole by creating a virtual Earth-sized telescope

Technique: very-long-baseline interferometry (VLBI)

Aiming to study the supermassive black hole in the center of Milky Way: Sagittarius A* (Sgr A*)

Observation started in April, 2017; pictures taken will be released for public in the end of 2017

Event Horizon Telescope

Event Horizon Telescope

Author: Wolf Damm Published: October 13th, 2011. “Astronomy Source.” Astronomy Source RSS, www.astronomysource.com/tag/event-horizon-definition/.

“Black Hole.” Wikipedia, Wikimedia Foundation, 24 Sept. 2017, en.wikipedia.org/wiki/Black_hole.

Contributor, Nola Taylor Redd Space.com. “Black Holes: Facts, Theory & Definition.”Space.com, www.space.com/15421-black-holes-facts-formation-discovery-sdcmp.html.

“Cygnus X-1.” Wikipedia, Wikimedia Foundation, 20 Sept. 2017, en.wikipedia.org/wiki/Cygnus_X-1.

Dunbar, Brian. “What Is a Black Hole?” NASA, NASA, 21 May 2015, www.nasa.gov/audience/forstudents/k-4/stories/nasa-knows/what-is-a-black-hole-k4.html.

“Event Horizon Telescope.” Event Horizon Telescope, eventhorizontelescope.org/.

Falkiyat. “Black Hole–World's Greatest Mysteries.” Falkiyat, 17 July 2017, falkiyat.com/black-hole-worlds-greatest-mysteries/.

“Gravitational Singularity.” Wikipedia, Wikimedia Foundation, 8 Sept. 2017, en.wikipedia.org/wiki/Gravitational_singularity.

“Neutron Star.” Wikipedia, Wikimedia Foundation, 21 Sept. 2017, en.wikipedia.org/wiki/Neutron_star.

“Nuclear Fusion.” Wikipedia, Wikimedia Foundation, 21 Sept. 2017, en.wikipedia.org/wiki/Nuclear_fusion.

“Schwarzschild Radius.” Wikipedia, Wikimedia Foundation, 13 Sept. 2017, en.wikipedia.org/wiki/Schwarzschild_radius.

“Singularity.” Wikipedia, Wikimedia Foundation, 21 Sept. 2017, en.wikipedia.org/wiki/Singularity.

Sloan Digital Sky Survey Press Office in Baltimore, Maryland | Published: Wednesday, May 25, 2016. “Supermassive Black Holes Cause Galactic-Scale Warming.” Astronomy.com, www.astronomy.com/news/2016/05/supermassive-black-holes-cause-galactic-scale-warming.

“Stellar Evolution.” Wikipedia, Wikimedia Foundation, 21 Sept. 2017, en.wikipedia.org/wiki/Stellar_evolution.

“Supernova.” Wikipedia, Wikimedia Foundation, 22 Sept. 2017, en.wikipedia.org/wiki/Supernova.

“Tolman–Oppenheimer–Volkoff Limit.” Wikipedia, Wikimedia Foundation, 22 Sept. 2017, en.wikipedia.org/wiki/Tolman%E2%80%93Oppenheimer%E2%80%93Volkoff_limit.

“White Dwarf.” Wikipedia, Wikimedia Foundation, 23 Sept. 2017, en.wikipedia.org/wiki/White_dwarf.