Simplified picture of the Carbon-Nitrogen-Oxygen fusion cycle
University of Oregon

The Carbon-Nitrogen-Oxygen Fusion Cycle

When the temperature of the core of a star reaches about 16 million kelvins (that's REALLY hot!), Helium is made through another fusion cycle. This cycle is named the Carbon-Nitrogen-Oxygen (CNO) cycle. Here Carbon gets the cycle going, but it is not used up.

Watching the movie below may help you to understand this process.

Last modified May 10, 2010 by Randy Russell.

You might also be interested in:

Fusion Inside the Stars

Fusion in the core of stars is reached when the density and temperature are high enough. There are different fusion cycles that happen in different phases of the life of a star. These different cycles...more

The Hydrogen Fusion Process

In the basic Hydrogen fusion cycle, four Hydrogen nuclei come together to make a Helium nucleus. This is the simple version of the story. There are actually electrons, neutrinos and photons involved in...more

The Neutron Capture Process

Neutron capture can occur when a neutron approaches a nucleus close enough for nuclear forces to be effective. The neutron is captured and forms a heavier isotope of the capturing element. When the new...more

The Supernova

A Supernova is a very massive star that explodes at the end of its life. The supernova is where the heavy elements (heavier than iron) are made. ...more

IMF

The Sun acts like it has a big magnet in the middle of it. We call this the Sun's magnetic field. The Sun's magnetic field has a fancier name, the Interplanetary Magnetic Field (IMF). This just means that...more

Fusion Reactions

The center of an atom is called the nucleus. Nuclei is the plural of nucleus. When two atoms come together, and their nuclei combine, you have fusion. Fusion releases energy. By using Einstein's famous...more

The Cherenkov Effect

The theory of relativity states that no particle can travel at the speed of light in a vacuum. However, light travels at lower speeds in dense media, like water. A particle traveling in water must have...more

Neutrino detectors

Neutrino interactions with matter are extremely rare, so detecting a neutrino is very hard. Neutrino detectors are typically large, underground tanks filled with a fluid that reacts to neutrinos. In neutrino...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA