Stars and Planets » Massive Stars

Although the Sun is in the top 15 % of the most massive stars there are quite a number of stars which are more massive. There are a small number of stars that are 8 solar masses or more. They burn far faster than the Sun and end their comparatively short lives in enormous explosions called supernovae which results in enormous quantities of material being flung out into interstellar space. A remnant from the core is left behinds a neutron star, a quark stars or a black hole depending on the mass of the exploding star. These stars are of enormous importance since they produce all the chemical elements of the periodic table after hydrogen, helium, lithium and beryllium. If these massive stars did not reach enormous temperatures needed to produce all the other members of the periodic table life would not exist. When most of the hydrogen is 'burnt' to helium the temperature rises. At about 100 million degrees Celsius, the helium nuclei 'burn' to carbon and at a slightly higher temperature carbon nuclei and helium nuclei burn to oxygen. Massive stars burn extremely rapidly especially in the later stages just before the supernova explosion occurs. A number of different reactions take place which give rise to many different nuclei leading up to the final production of nickel-56 which undergoes radioactive decay by two stages to iron-56. The way the nucleosynthetic processes operate in stars is that the fuel burns to produce the ash which becomes the fuel for the next process.

» Alpha Particle Nucleosynthetic Pathways are among the most important «

Hydrogen is the fuel for the first burning - the ash is Helium-4 pp Series and CNO
Helium-4 is the fuel for the second burning - the ash is Carbon-12 Triple Alpha via 8Be
Carbon-12 is the fuel for the third burning - the ash is Oxygen-16 12C + 4He → 16O + γ
Oxygen-16 is the fuel for the fourth burning - the ash is Neon-20 16O + 4He → 20Ne + γ
Neon -20 is the fuel for the fifth burning - the ash is Magnesium-2420Ne + 4He → 24Mg + γ
Magnesium-24 is the fuel for the sixth burning - the ash is Silicon-28 24Mg + 4He → 28Si + γ
Silicon-28 is the fuel for the seventh burning - the ash is Sulphur-32 28Si + 4He → 32S + γ
Sulphur-32 is the fuel for the eighth burning - the ash is Argon-36 32S + 4He → 36Ar + γ
Argon-36 is the fuel for the ninth burning - the ash is Calcium-40 36Ar + 4He → 40Ca + γ
Calcium-40 is the ash for the tenth burning - the ash is Titanium-44 40Ca + 4He → 44Ti + γ
Titanium-44 is the fuel for the eleventh burning - the ash is Chromium-48 44Ti + 4He → 48Cr + γ
Chromium -48 is the fuel for the twelfth burning- the ash is Iron-52 48Cr + 4He → 52Fe + γ
Iron-52 is the fuel for the thirteenth and burning - the ash is Nickel-56 52Fe + 4He → 56Ni + γ
Nickel-56 is highly radioactive and decays via Cobalt-56 to Iron-56 a stable isotope

As a result of the successive 'thermonuclear burning' processes all the stable isotopes of the common elements up to and including iron are produced. This includes the elements essential to life carbon, oxygen, sulphur, phosphorus, sodium, potssium, magnesium, calcium, chlorine iron and most trace elements.

Some of the most important pathways are outlined above. The series shown is an over simplification of what occurs in the interiors of very massive stars since many other reactions also take place. The successive addition of Helium-4 is only one of the typical pathways. Although sodium and potassium are not produced in the alpha particle pathway they are made by side reactions in large amounts. Nitrogen is produced in considerable amounts by the CNO process.

Conditions in the cloud of material ejected from the explosion are so energetic that all the other elements beyond iron in the periodic table are produced. Some of these like copper, zinc, and iodine are also found in living organisms.

Therefore the saying that we are all the product of stardust is very true.

Ray Goodwin

Somewhere there are mountains
Glistening in the snow
Somewhere there are mountains
That we shall never know

Somewhere there are rivers
Flowing fast and free
Somewhere there are rivers
That we can never see

Somewhere there are oceans
And sun drenched island sands
Forests full of creatures
In vastly distant lands

Somewhere there’s a planet
Beneath an alien star
The people watch our tiny sun
And wonder where we are

One day perhaps we’ll find them
Across the void of space
Perhaps through ways as yet unknown
We’ll meet them face to face

The author of this web site Ray Goodwin holds B.Sc. Degrees from London University in Chemistry, Geology and Physiology and an M.Sc. in Biochemistry. He has spent most of his professional life teaching in Colleges of Technology. On his retirement he has entered the fields of astronomy, astrochemistry, astrobiology and space sciences. He has spent a great deal of his retirement in visiting amateur astronomy societies and in attending European Space Agency Symposia in ESTEC in the Netherlands and other scientific conferences in England and Sweden. He regularly attends the yearly European Astrofest in South Kensington London and other meetings in the UK. He has written scientific articles and given a number of lectures on diverse scientific subjects.

Readers of this web site are invited to e-mail the author ( and discuss their opinions of the topics dealt with and suggest any changes which they think may be helpful.

Life in the Cosmos Website
Version 01.00 - April 20, 2015.