Stars
In the beginning the universe was filled with large clouds of dust and gas. Some of these clouds began to squeeze under their own gravitational pull. In each of these clouds the matter began to pack together until it became hot. A star was born. Stars still forming in that manner are called nebulas. One example is the Orion nebula, a gaseous collection in the constellation Orion. Astronomers with high powered telescopes can see black spots on the nebula. These spots are clouds collapsing that will eventually become shining stars. Stars don't stay still. They are constantly moving. Some twinkle, some explode, some, collide, and some swallow light.
It's hard to escape the gravitational pull of small objects packed tightly with matter. For example the gravity of a neutron star is almost impossible for an object to escape. Only fast-moving gas, radiation, radio waves ,and light can possibly escape.
The universe is full of things that amaze us. In the past, one such group of things looked like faint stars. At first in the late 1950's astronomers thought these things were stars from our own galaxy,known as the Milky Way. Scientists found that these shining objects were different since they had radio waves! So astronomers watched their light more closely.
In 1963 it was decided that these things were between one and ten billion light years away. Astronomers soon found more of these stars that were not radio waves but just as distant. In 1987 astronomers from America and Great Britain found an object that was 12 billion light years away. These objects normally wouldn't be noticed but they weren't normal. Their centers were unusually bright! They were as much as one hundred times brighter than normal galactic centers.
The word Quasar comes from two different words , quasi and stellar together. These words mean "starlike." What makes a quasar bright? It may be that black holes are at their centers. These black holes could pull in anything, including stars.
A black hole is a place in space that has lots of mass packed into a tiny space about the size of Earth. Its gravity is so intense that, in some cases, not even light can escape. In 1784, the English geologist, John Michell, realized that it would be possible for gravity to be so great that nothing could escape not even light or radio waves, each traveling at 186,000 miles per hour. So that means (if it were possible) you could shine a flashlight in front of you and see the light at your feet because light cannot travel in the extreme gravity of a black hole.
Some scientists believe that black holes are just whirlpools in space and that what goes in must come out. They are saying that black holes are the vacuum cleaners of space. Although black holes had not been found before, scientist have a good reason to believe they exist. Just ask one of them.
A supernova is an exploding star that becomes a billion of times brighter than the sun before gradually fading from our view of the universe. At it's brightest point an exploding star, or supernova, may light up a whole galaxy. The explosion throws very large clouds of dust and gas into space. The expelled mass may grow to twice the size of the sun. There are two types of supernova, type1 and type 2. Type one supernovas occur in certain binary stars. A binary star is a pair of stars that orbit each other. If two stars are close enough together, the gravitational pull of the white dwarf draws mass from it's larger companion. When the white dwarf's mass grows to be about 1.4 times that of the sun, it collapses under it's own weight, and then explodes.
A type 2 supernova results from the death of a single star much more massive than that of our own sun. When such a star begins to burn out, it's mass causes it to collapse very quickly. Lots of energy is released in the form of neutrinos (a type of subatomic particle) and electromagnetic radiation (electric and magnetic energy). This causes a star to erupt into a supernova.