Black Holes By Emma Sharon, Carolina Ratcliff & Georgia Gray

What is a black hole?

A region in space where the gravitational pull is so strong that light cannot escape
This occurs because matter has been pressed into a tiny space
This usually happens at the end of a star's life


The smallest black holes are called primordial black holes. Scientists believe this type of black hole is as small as a single atom and have "the mass of a large mountain." They are said to have formed soon after the big bang.

A medium sized black hole is called a stellar black hole. It is the most common type, and has a mass up to 20 times greater than the mass of the sun. It is assumed that dozens of stellar black holes are in the Milky Way galaxy. These black holes form when the center of a very massive star collapses in upon itself. (This also causes a supernova that blasts part of the star into space).

The largest black holes are called supermassive, with masses greater than 1 million suns combined. Scientists assume that every galaxy has one supermassive galaxy at the center, and the one in the center of our Milky Way galaxy is called Sagittarius A. It is assumed that supermassive black holes were formed at the same time as the galaxy it is in.

How do we know they exist?

scientists can see the effects of a black hole's strong gravity on the stars and gases around it.
sometimes this gravity is so strong that it pulls at the gases of a star and grows an "accretion disk." The gas gets very hot and releases x-ray light, which can be measured by NASA telescopes.
When a black hole and a star are orbiting close together, high-energy light is produced. Scientific instruments can see this high-energy light.

How is NASA studying black holes?

The Chandra X-Ray Observatory is a telescope that detects X-Rays from areas in the universe. These x-rays usually alert scientists to exploded stars and black holes. It orbits above the earth's atmosphere at an altitude of 86,400 miles, and is controlled by scientists at Harvard University in Cambridge, MA.

Launched in November of 2004, the Swift Satellite works to identify gamma ray bursts, which often indicate the creation of a black hole. It takes photographs of the GRBs and their afterglows, and releases the data to the public.

The Fermi Gamma-ray Space Telescope was launched in June of 2011 and observes photons with energy levels thousands to hundreds of billions of times greater than what the unaided eye can see. It was developed in collaboration with the U.S. Department of Energy, along with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the U.S, and is operated out of Stanford University.



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