Plasma is one of the four states of matter, along with gases, liquids, and solids. Most people don’t think about plasma in their daily lives the way they think about other states of matter, but it makes up 99% of the visible matter in the universe. Much of this is astrophysical plasma—the plasma that exists in outer space (for example, in nebula) and that is contained within stars including the Sun.
In plasma, some of the electrons separate and become free from neutral atoms (atoms that have an equal number of protons and electrons and thus a neutral charge). The resulting free electrons makes plasma different from the other states of matter, where the electrons are held close to nuclei.
When the atoms in plasma separate from their negatively charged electrons, they no longer have a neutral electrical charge. Instead, the atoms become ions—positively charged particles. Therefore, plasma is an ionized state made up of positively charged ions and negatively charged electrons.
There are several reasons why electrons in atoms can separate and form plasma. In laboratory experiments, scientists can blast the atoms with high-voltage electricity, lasers, or electromagnetic fields to form plasma. In space, plasma may form from high-energy photons including gamma rays striking atoms. Plasma can also form in space when gravity increases pressure so much that the pressure super heats gases. The high temperatures cause atoms to collide with each other, resulting in the electrons separating from the atoms, creating plasma and the beginnings of a star.
This process of gases being superheated to create plasma suggests that gases and plasma have a relationship similar to how liquid can be a heated form of a solid. This analogy is not always correct. For one, unlike gas, plasma can conduct electricity. Also, in gases, all the particles behave in similar ways. In plasma, however, electrons and ions behave and interact in very complex ways, which creates waves and instabilities.
Plasmas come in several types. Most plasma in the universe is what researchers call high-temperature plasmas. In these high-temperature plasmas, temperatures can be more than 10,000 degrees Fahrenheit, and all the atoms can be fully ionized. Low-temperature plasmas are different. The atoms are only partially ionized, and they can be incredibly cool—even room temperature. Another unusual type of plasma is high-energy density plasma, which scientists create in laboratories to study their unusual properties.
DOE Office of Science: Contributions to Plasma Research
Studying plasma helps scientists understand matter. It also helps them progress toward the goal of fusion energy. The Department of Energy (DOE) Office of Science supports research into plasma through its Fusion Energy Sciences and Nuclear Physics programs. DOE-funded research on plasma has also improved the manufacturing of the semiconductors found in everything from phones and computers to cars. Expertise in plasma helped researchers at the DOE National Laboratories develop ways to control the creation of semiconductors on an atom-by-atom level.
Fast Facts
- One type of lightning – ball lightning – is plasma. Learn more from the Max Planck Institute.
- The aurora borealis is also caused by plasma. Learn more in this science highlight.
- Confining plasma is an important step in designing fusion tokamak and stellarator devices that may eventually provide us with fusion power.
- High-energy density plasma science enabled fusion ignition in laboratory conditions.
Resources
- The DOE Office of Science Nuclear Physics program
- The DOE Office of Science Fusion Energy Sciences program
- The DOE Office of Science funds extensive research on plasma for fusion power. Learn about this work from DOE’s science highlights.
Scientific terms can be confusing. DOE Explains offers straightforward explanations of key words and concepts in fundamental science. It also describes how these concepts apply to the work that the Department of Energy’s Office of Science conducts as it helps the United States excel in research across the scientific spectrum.