Black Hole

Franz Artur Viehböck

Frist Austrian in space . ( Born August 24, 1960 in Vienna) is an Austrian electrical engineer, and was Austria's first astronaut, and thus titulated „Austronaut“ by his country's media. He visited the Mir space station in 1991 aboard Soyuz TM-13, returning aboard Soyuz TM-12 after spending just over a week in space.

Together with Clemens Lothaller, he was selected for the Soviet-Austrian space project Austromir 91. After two years of training he was chosen for the mission, and launched on October 2, 1991 together with the Russian cosmonauts Alexander A. Volkov and the Kazakh Toktar Aubakirov in Soyuz TM-13 from the Baikonur Cosmodrome spaceport.

At the Mir space station he conducted 15 experiments in the fields of space medicine, physics and space technology, together with the cosmonauts Anatoly Artsebarsky and Sergey Krikalev. Viehböck returned after 7 days and 22 hours with Soyuz TM-12, and landed in Kazakhstan on October 10.

The following two years he gave numerous lectures on the mission, then went to the United States and worked for Rockwell.

Yang Liwei

First Chinese national in space.

( Born June 21, 1965) is a major general and military pilot and China National Space Administration astronaut. In 2003, he became the first person sent into space by the Chinese space program. This mission, Shenzhou 5, made China the third country to independently send humans into space.

Yang was selected as an astronaut candidate in 1998 and has trained for space flight since then.He was chosen from the final pool of 13 candidates to fly on China's first manned space mission. A former fighter pilot in the Aviation Military Unit of the PLA, he held the rank of Lieutenant Colonel at the time of his mission. He was promoted to full Colonel on October 20, 2003.He was launched into space aboard his Shenzhou 5 spacecraft atop a Long March 2F rocket from Jiuquan Satellite Launch Center at 09:00 CST (01:00 UTC) on October 15, 2003. Prior to his launch almost nothing was made public about the Chinese astronaut candidates; his selection for the Shenzhou 5 launch was only leaked to the media one day before the launch.Yang Liwei has reported the apparition of abnormal vibrations 120 seconds after launch, he described as "very Uncomfortable". As a consequence, corrective measures were swiftly taken to the design of the following CZ-2F carrier rocket for the Shenzhou-6.

Yi So-yeon

First South Korean in space

studied at Gwangju Science High School. She earned bachelor’s and master’s degrees with a focus on mechanics at KAIST in Daejeon. Her doctor in biotech systems was conferred on 29 February 2008 in a ceremony at KAIST although she was unable to be present due to her training commitments in Russia.

Yi was one of the two finalists chosen on 25 December 2006 through the Korean Astronaut Program. On 5 September 2007, the Korean Ministry of Science and Technology chose Ko San, over Yi So-yeon, following performance and other tests during their training in Russia.On 7 March 2008, she was selected to train with the primary crew, and on 10 March the Ministry of Education, Science and Technology announced that Yi would replace Ko. This was after the Russian Federal Space Agency asked for a replacement because Ko violated regulations several times at a Russian training center by removing sensitive reading materials and mailing one back to Korea. On 8 April 2008, Yi was launched into space on board Soyuz TMA-12, with two Russian cosmonauts. South Korea is reported to have paid Russia $20 Million for Yi's space flight. She makes South Korea the third country, after the United Kingdom and Iran, to have a woman as its first space traveler.

Fyodor Nikolayevich Yurchikhin

First Georgian-born man in space

(Russian: Фёдор Николаевич Юрчихин, Greek: Θεόδωρος Γιουρτσίχιν του Νικόλαου; born 3 January 1959), is a Russian cosmonaut of Greek descent and RSC Energia test-pilot who has flown on three spaceflights.

His first spaceflight was a 10-day Space Shuttle mission STS-112. His second was a long-duration stay aboard the International Space Station (ISS) as a Flight Engineer for Expedition 15; for this mission he was launched in the Soyuz TMA-10 spacecraft. He has undertaken two further long-duration stays aboard the ISS, as a crew member of Expedition 24 / 25.

For this mission he was launched with the spacecraft Soyuz TMA-19, and he landed in November 2010, also with the TMA-19 spacecraft. He served as Soyuz Commander for his fourth mission aboard Soyuz TMA-09M, as Flight Engineer for Expedition 36 and ISS Commander for Expedition 37.

After graduation from high school in Batumi in 1976, he entered the Moscow Aviation Institute named after Sergey Ordzhonikidze. He finished studying in 1983, and is qualified as a mechanical engineer, specializing in airspace vehicles. In 2001, he graduated from the Moscow Service State University with a Ph.D. in economics.

What is black hole ?

A black hole is a region of spacetime from which nothing can escape, even light .It is impossible to see a black hole directly because no light can escape from them; they are black. But there are good reasons to think they exist. When a large star has burnt all its fuel it explodes into a supernova. The stuff that is left collapses down to an extremely dense object known as a neutron star. We know that these objects exist because several have been found using radio telescopes.
The hole is called "black" because it absorbs all the light that hits the horizon, reflecting nothing, just like a perfect black body in thermodynamics. Quantum field theory in curved spacetime predicts that event horizons emit radiation like a black body with a finite temperature. This temperature is inversely proportional to the mass of the black hole, making it difficult to observe this radiation for black holes of stellar mass or greater.
A supermassive black hole (SMBH) is the largest type of black hole, on the order of hundreds of thousands to billions of solar masses.
Active galactic nuclei (AGN) are galaxies that have very energetic central regions, due to either the presence of a black hole or star formation activity at the core of the galaxy.
Objects whose gravity fields are too strong for light to escape were first considered in the 18th century by John Michell and Pierre-Simon Laplace. The first modern solution of general relativity that would characterize a black hole was found by Karl Schwarzschild in 1916, although its interpretation as a region of space from which nothing can escape was first published by David Finkelstein in 1958. Long considered a mathematical curiosity, it was during the 1960s that theoretical work showed black holes were a generic prediction of general relativity. The discovery of neutron stars sparked interest in gravitationally collapsed compact objects as a possible astrophysical reality.

Who invented Black hole ?

Albert Einstein first predicted black holes in 1916 with his general theory of relativity. The term "black hole" was coined in 1967 by American astronomer John Wheeler, and the first one was discovered in 1971.

When Black hole is formed ?

Black holes of stellar mass are expected to form when very massive stars collapse at the end of their life cycle. After a black hole has formed it can continue to grow by absorbing mass from its surroundings. By absorbing other stars and merging with other black holes, supermassive black holes of millions of solar masses may form. There is general consensus that supermassive black holes exist in the centers of most galaxies.

Properties of black hole :

The simplest static black holes have mass but neither electric charge nor angular momentum. These black holes are often referred to as Schwarzschild black holes after Karl Schwarzschild who discovered this solution in 1916.[9] According to Birkhoff's theorem, it is the only vacuum solution that is spherically symmetric.

What is Hawking radiation ?

In 1974, Hawking showed that black holes are not entirely black but emit small amounts of thermal radiation; an effect that has become known as Hawking radiation. By applying quantum field theory to a static black hole background, he determined that a black hole should emit particles in a perfect black body spectrum. Since Hawking's publication, many others have verified the result through various approaches.[85] If Hawking's theory of black hole radiation is correct, then black holes are expected to shrink and evaporate over time because they lose mass by the emission of photons and other particles.[32] The temperature of this thermal spectrum (Hawking temperature) is proportional to the surface gravity of the black hole, which, for a Schwarzschild black hole, is inversely proportional to the mass. Hence, large black holes emit less radiation than small black holes.

Types of black hole
There are three types: stellar black holes, supermassive black holes and intermediate black holes.

1] Stellar black holes :

When a star burns through the last of its fuel, it may find itself collapsing. For smaller stars, up to about three times the sun's mass, the new core will be a neutron star or a white dwarf. But when a larger star collapses, it continues to fall in on itself to create a stellar black hole.
Astronomers suspect that most black holes are produced when massive stars (at least 8-10 times the Sun's mass) reach the end of their lifecycle. Inside a star, gravity tries to pull matter closer together. While a star is glowing, it is consuming its fuel through a nuclear process known as fusion. It radiates not only light, but heat as well. The pressure of the heated gases pushing outward balances the force of gravity pulling inward. Once the star's nuclear fuel has been depleted, the star becomes unstable and the core implodes causing the outer shell to explode in a supernova. If the remnant core that remains after the supernova is less than 3 solar masses, gravity compresses the electrons and protons so that neutrons form. The pressure of neutrons in contact with each other counteracts the forces of gravity. This stable core, which is now composed almost entirely of neutrons, forms a neutron star. Neutron stars possess tremendous mass and consequently have a very powerful gravitational pull. If the remnant left after the supernova is greater than 3 times the Sun's mass, not even the neutron pressure can counteract gravity and the remaining material will continue to contract. The remnant collapses to the point of essentially zero volume (yet it has infinite density!). This creates a mathematical singularity. A singularity resides in the center of all black holes.
A spherical region known as the event horizon marks what scientists call the “boundary” of a black hole. It is given this name because information about events which occur inside this region can never reach us. The distance from the singularity to the event horizon is known as the Schwarzschild radius, after the German physicist who predicted the existence of a "magic sphere" around a very dense object. Inside the region, he theorized, gravity would be so powerful that nothing could escape from it, i.e., the gravitational pull would be so strong that the velocity necessary to escape the pull is unobtainable. A black hole has such an enormous concentration of mass in such a small volume that in order to escape from it, an object would have to be moving at a speed greater than the speed of light. At this time we know of nothing that can attain the necessary velocity.
Remember that a stellar black hole was once a star. Most stars have a companion star to which they are bound in a binary system. This nearby companion can be a source of material on which the black hole “feeds”. Matter can be pulled off the companion in large swirling streams of hot gas that spiral toward the black hole as a fast moving incandescent whirlpool known as an accretion disk. As the matter in the disk falls closer to the black hole, it heats up and gives off radiation such as X-rays. By measuring the motion and radiation from an accretion disk, astronomers are able to infer the presence and mass of the black hole. When all of the material in the accretion disk has been consumed, the disk disappears and the black hole is virtually undetectable. Stars and planets at a safe distance from the black hole's event horizon will not be pulled in toward the black hole. They will instead orbit the black hole just as the planets orbit the Sun in our solar system. The gravitational force on stars and planets orbiting a black hole is the same as when the black hole was a normal star.

2] Supermassive Black Hole :

Supermassive black holes have masses comparable to those of a typical galaxy. These masses range anywhere from 10 billion to 100 billion of our Suns. Supermassive black holes tend to be in the centers of galaxies, creating what are called Active Galactic Nuclei (AGNs). An AGN emits more energy than would be expected from a typical galactic nucleus. The answer as to why this is so lies in the presence of the supermassive black hole in the galactic center. In some AGN, the massive black hole and its accretion disk somehow produce outward-moving streams of particles that are projected away perpendicular to the disk. These streams are known as jets and have the power to accelerate electrons almost to the speed of light. This produces gamma-rays that can be detected by gamma-ray observatories. The most powerful AGNs in our Universe are called quasars. We have been able to detect quasars that reside 15 billion light-years away. Scientists believe that the study of quasars will provide information about the Universe during the time of early galaxy formation.

3] Intermediate black holes – stuck in the middle :

Scientists once thought black holes came in only small and large sizes, but recent research has revealed the possibility for the existence of midsize, or intermediate, black holes. Such bodies could form when stars in a cluster collide in a chain reaction. Several of these forming in the same region could eventually fall together in the center of a galaxy and create a supermassive black hole

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