You're probably familiar with the three states of matter: solid, liquid and gas. However, matter actually has a fourth state, which is called plasma. Although not the most common type of matter here on Earth, scientists say plasma is the most abundant type of regular matter there is; more than 99 percent of the visible universe is composed of plasma [source: CPS]. Plasma is created when gases are heated to extremely high temperatures or otherwise excited by powerful amounts of energy. At high enough energy levels, atoms begin to physically come apart, shedding electrons until they become a soup of detached subatomic particles. Another way of explaining this is to simply say that plasma is highly ionized gas. Plasma can occur naturally -- stars are made of plasma -- or scientists can create plasma in the laboratory.
Just how hot can plasma get? Well, since we know that the sun is made of plasma, it's obvious that the stuff can get pretty hot. But for decades, scientists have been puzzled as to why the outer layer of the sun's atmosphere, called the corona, was so hot -- hotter, in fact, than the surface of the sun. Data from spacecraft has shown that plumes of plasma called spicules emanate from the lower atmosphere of the sun. While we'd call most of them pretty hot at tens of thousands of degrees Celsius, those spicules are merely a bit toasty when you compare them to other spicules that register temperatures of at least 1 million to 2 million degrees Celsius (1.8 million to 3.6 million degrees Fahrenheit) [source: Matson]. While these ultra-high heat spicules aren't as common, some scientists believe they occur often enough to heat the corona. Scientists don't know why they form, however.
While the plasma on the sun is the hottest we know of in the natural world, manufactured plasma is much hotter. Several machines called tokamaks create fusion reactions in labs around the world. The ITER tokamak, a fusion machine, is currently under construction in France. ITER, an international coalition of scientists from six countries and the European Union, hopes to use the tokamak to test ideas for fusion energy production. The tokamak will use magnetic forces to heat two hydrogen isotopes to more than 150 million degrees Celsius (about 270 million degrees Fahrenheit). This will break the gas down into plasma. As in a star, this superheated plasma will allow light elements to fuse and yield energy [source: ITER].
To cut one of our hardest materials -- metal -- a pressurized inert gas (such as nitrogen, argon or oxygen) passes through a channel in a cutter past an electrode, and an electrical spark ignites the gas into the fourth state of matter: plasma. The stream of superheated burning gas can reach a temperature of about 30,000 degrees Fahrenheit (16,649 degrees Celsius). It is not only ultrahot, but also moves super fast through the molten metal, at about 20,000 feet per second (6,096 meters/second).
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