Black Holes- Facts and Info

History of the term Black hole is quite interesting. In 1687 Sir Isaac Newton first described the term gravity in his publication “Principia”. We all know that gravity of black hole gives nightmare to scientists. In 1783 John Michell predicted that there might exist an object whose escape velocity is more than the speed of light. Albert Einstein predicted the space-time curvature in his theory of Relativity in 1915. In 1916 Karl Schwarzschild's using Einstein’s theory of relativity explained Blackhole and also defined the gravitational radius of a black hole, which afterward called as Schwarzchild radius. After that, black hole theory was strongly opposed unless John Wheeler came in and coined the term Black hole again. In 1964 neutron stars were discovered and in 1970 Stephen Hawking described the black hole briefly. In 1994 Hubble telescope provided the best evidence of supermassive black holes.

Image Credit: NASA/CXC/M.Weiss

Black holes are the most interesting objects in the universe. A black hole is, in fact, a large amount of matter packed into a small area. Nothing can escape from the black hole, not even light. The formation of a black hole is quite interesting phenomena. The formation of the black hole takes place when any object reaches a critical amount of density and its gravity causes to collapse to a small point. There are two types of black holes, stellar black holes, and supermassive black holes. Stellar black holes are mostly formed when a star less 100 times to that of the sun’s mass collapses. In reality, an end of a star is a beginning of a black hole. If a star is massive as three times the mass of the sun than theoretically it can be proved that no force can save a star from collapsing under its own gravity. In the case of our sun, the chances of forming a black hole are none because our sun’s mass does not fulfill the criteria. Stellar black holes are formed by an explosion. When a star runs out of fuel then it collapses and forms a supernova and remaining matter forms a black hole.

In the case of Super Massive Hole we are not quite sure what causes the formation of a super massive black hole, but it is pretty sure that super massive black holes are more massive than a stellar black hole. Some say that a group of stellar black hole together after merging makes super massive black holes. One possibility is that in early ages of the universe some stellar black holes are formed and with time they are transformed to a super massive black hole.

Scientists think that there is no middle category of a black hole, but recent indications from Chandra, XMM-Newton and Hubble are giving strength to a middle category of Black holes. Around 20 X-ray binary systems that are thought to contain stellar black holes have been discovered and this number continues to increase the sensitivity of tool advances. The Large Hadron Collider in Switzerland that may reach energies high enough to create tiny black holes.

Planets-Definition and Facts

If you look throughout the history for the definition of what really a planet has actually changed always with time and meant different things at the same moment depending on what kind of person was defining it. Now we all know about Ceres because of advanced technology and telescopes. Ceres was discovered in 1801 and was in start thought to be a planet like our home Earth and other known planets of our solar system until astronomer discovered another heavy body in space named "Pallas" that has a similar orbit which affected their thought about Ceres. Astronomers of that time, even using the available technology of their time, were somehow able to tell that these objects were not actually planets. The famous astronomer of that time Sir William Herschel suggested the name "asteroids" for this kind of bodies in space and which got stuck with time.Asteroids at that time were then accepted as a totally distinct category of bodies in space.

A few years ago, you might have said that a planet can be defined as one of the nine large and heavy celestial bodies that orbit the Sun. However, with new technology, which also made the discovery of many other new celestial bodies in various regions of our solar system, such as the Kuiper Belt, also created problems for astronomers like determining "what a planet is" a little more difficult. While many of astronomers suggested various definitions for the term planets over the years but unfortunately none of them were widely accepted by other astronomers.

The issue of defining what planet is when came to a head in 2005 when an object even larger than Pluto was discovered far beyond the Kuiper Belt by astronomers. This object, which is now known as Eris, was a source of division among many astronomers. Some astronomers wanted Eris to be the part of our solar system as a tenth planet while others just considered it to be just another asteroid like many others in Kuiper belt, despite the fact that it is larger than Pluto is. The International Astronomical Union (IAU), which usually resolves problems and issues like this, met in 2005 at a conference, but instead of debating and resolving this issue, they did not come up with any agreement upon the definition of a planet. After the conference of 2005, the matter was resumed in summer of 2006 again at the next IAU conference.

In August 2006, the IAU finally agreed in conference upon a definition for “what actually a planet is”. The IAU’s official definition for defining a planet now is:-

“A planet is a celestial body that (1) is orbiting the Sun, (b) and it must have sufficient mass for its self-gravity in order to overcome rigid body forces so that it assumes a definite hydro-static equilibrium (nearly round) shape, and (c) must has cleared the neighborhood around its orbit.”

An object that has cleared the path of its orbit and neighborhood of its orbit and it is of sufficient size in order to retain its nearly round shape with the help of self-gravity. While defining “what a planet is”, the IAU also created a new category for some bodies orbiting the Sun as a “dwarf planets”, after which Pluto was categorized as a dwarf planet. Eris and several other objects were also categorized as a dwarf planet depending on their characteristics. The definition has had severe opposition since, especially with many people and astronomers angry at the demotion of Pluto (Which actually does not matter at all).