Ask A Scientist

How does the sun burn if there is no oxygen in space?

Asked by: Brennen Levis/Steven Salvatore
School: St. James/Maine Endwell Middle Schl.
Grade: 7
Teacher: Mrs. Hantsch/Mr. Underwood
Hobbies/Interests: Brennen: soccer, reading, fishing, and just about every outdoor sports opportunity Steven: football, lacrosse, basketball, skiing  

Answer from Douglas W. Green

Adjunct Lecturer, Binghamton University

Research areas: Leadership and Instructional data analysis
Family: Daughter Lena, age 24, who is an animator in New York City.
Interests/hobbies: Playing my banjo, biking, golf and reading


Fires that we are familiar with need something that can burn like wood, coal, or oil and a steady source of oxygen from the air around us. Since the sun does not have an atmosphere containing oxygen like Earth’s, there must be some other kind of “burning” that allows the sun to provide the earth with light and warmth. This other kind of burning is the result of one kind of nuclear energy known as fusion. All matter is made of very small atoms and atoms contain a nucleus surrounded by and electron cloud. If two atoms are pressed together hard enough they can combine or fuse to form a single, larger atom. When this happens, some mass is lost and converted into energy. The amount of energy you get can be calculated by Albert Einstein’s famous E = MC2 equation which is pronounced E equals M C squared. To square a number you multiply it by itself. The C in this equation is the speed of light, which is 186,000 miles per second. The sun is made mostly of hydrogen, which is the lightest of all elements. Most of the energy the sun gives off results from hydrogen atoms combining to form helium, the second lightest element. The reason this happens on the sun and all other stars and not on planets like the earth is due to the sun’s mass. The sun is over 330,000 times as heavy as the Earth. The force of gravity that holds us to the earth is much stronger on the sun. It is so strong that it causes atoms inside the sun to combine or fuse to form larger atoms and the energy that allows the sun to “burn”. The amount of mass converted to energy is a small amount of the total mass of the fused atoms, but it doesn’t take much mass to make a lot of energy. Even though hydrogen fusing to make helium produces most of the sun’s energy, larger atoms like helium also fuse to make an assortment of larger atoms. That is how all of the other elements that make up the earth and our bodies were formed. Stars that are larger than our sun have gravity strong enough so that the fusion process goes fast enough so that the star explodes. These explosions are called novas or super novas.

During novas, very heavy elements are formed due to these tremendous forces of gravity. Scientists believe that our sun and its planets were formed from the remains of exploded stars. So in a sense, we are stardust. If you want to see pictures that show the size of our sun and its planets and our sun and other stars, check the following Internet address:

Last Updated: 3/1/17