Science Library - free educational site

Fusion

What makes the Sun tick?

Fusion is the combining of two nuclei to form a new species, accompanied by the release of energy.

Fusion energy is a much-vaunted possible alternative means of generating electrical power, but the technology still illudes us. However, the fact remains that most of the universe is driven by fusion power: in stars.

Our Sun is mainly hydrogen:

ElementPercentage composition
Hydrogen73.46%
Helium24.85%
Oxygen0.77%
Carbon0.29%
Iron0.16%
Neon0.12%
Nitrogen0.09%
Silicon0.07%
Magnesium0.05%
Sulphur0.04%

The Sun has been burning hydrogen fuel for about 6 billion years, and is about half way through this phase of its life cycle. When it has depleted a critical amount of its hydrogen, its radiation pressure/gravity equilibrium will be lost. It will initially expand to one AU (distance Earth-Sun) radius, losing a third of its mass, before collapsing. At this stage, the star will continue with helium fusing, resulting in the fusing of carbon and oxygen. The exact evolutionary path of a star depends on its mass.

Sun profile

Hydrogen on Earth is mainly the $^1_1H$ isotope, meaning it has only one proton in its nucleus, with a single electron. There are rarer isotopes of $^2_1H$, deuterium, and $^3_1H$, tritium. The nucleus of a helium-4 atom is known as an alpha-particle.

Under the conditions of extreme pressure and temperature of the Sun, the following fusion reaction occurs:

$$4^1_1H {→} ^4_2He + 2^0_1e + 2^0_1ν_e + ^0_0γ$$

The combination of two nuclei with low binding energy will release energy and produce a nucleus with higher binding energy.

Content © Andrew Bone. All rights reserved. Created : March 1, 2014 Last updated :May 18, 2016

Latest Item on Science Library:

The most recent article is:

Air Resistance and Terminal Velocity

View this item in the topic:

Mechanics

and many more articles in the subject:

Subject of the Week

Universe

'Universe' on ScienceLibrary.info covers astronomy, cosmology, and space exploration. Learn Science with ScienceLibrary.info.

Science

Great Scientists

Lynn Margulis

1938 - 2011

Lynn Margulis was an American biologist who is considered one of the leading figures in the study of symbiosis in biological evolution.

Lynn Margulis
ZumGuy Network Promotions

Quote of the day...

Prediction is very difficult, especially about the future.

ZumGuy Internet Promotions

IT information forum by Sean Bone