The oxygen and heavier elements in our bodies were made in the nuclear furnace of high mass stars. High core temperatures allow helium to fuse with heavier elements. allow fusion to elements as heavy as iron. Advanced reactions in stars make elements like Si, S, Ca, and Fe.

High mass stars (stars with masses greater than three times the mass of the Sun) are the largest, hottest and brightest Main Sequence stars and blue, blue-white or white in colour. High mass stars use up their hydrogen fuel very rapidly and consequently have short lives.

High-mass stars are very luminous and short lived. They forge heavy elements in their cores, explode as supernovas, and expel these elements into space. Apart from hydrogen and helium, most of the elements in the universe, including those comprising Earth and everything on it, came from these stars.

High mass stars have to generate a lot of energy in order to balance the force of gravity. Therefore they are very hot and luminous. That explains their position high on the Main Sequence. On the other hand, low mass stars have to generate little energy in order to balance the force due to gravity.

High mass stars go through a similar process to low mass stars in the beginning, except that it all happens much faster. They have a hydrogen fusion core, but much of the hydrogen fusion happens via the CNO cycle. If the star is massive enough, the neutron star will collapse further and form a black hole.

Like low-mass stars, high-mass stars are born in nebulae and evolve and live in the Main Sequence. However, their life cycles start to differ after the red giant phase. A massive star will undergo a supernova explosion.

Seven Main Stages of a Star

• Giant Gas Cloud. A star originates from a large cloud of gas.
• Protostar. When the gas particles in the molecular cloud run into each other, heat energy is produced.
• T-Tauri Phase.
• Main Sequence.
• Red Giant.
• The Fusion of Heavier Elements.
• Supernovae and Planetary Nebulae.

All stars eventually run out of their hydrogen gas fuel and die. When a high-mass star has no hydrogen left to burn, it expands and becomes a red supergiant. While most stars quietly fade away, the supergiants destroy themselves in a huge explosion, called a supernova.

The exact stages of evolutions are:

• Subgiant Branch (SGB) – hydrogen shell burning – outer layers swell.
• Red Giant Branch – helium ash core compresses – increased hydrogen shell burning.
• First Dredge Up – expanding atmosphere cools star – stirs carbon, nitrogen and oxygen upward – star heats up.

Small stars have a mass upto one and a half times that of the Sun. Stage 1- Stars are born in a region of high density Nebula, and condenses into a huge globule of gas and dust and contracts under its own gravity. This image shows the Orion Nebula or M42 .

Formation of Stars Like the Sun

• STAGE 1: AN INTERSTELLAR CLOUD.
• STAGE 2: A COLLAPSING CLOUD FRAGMENT.
• STAGE 3: FRAGMENTATION CEASES.
• STAGE 4: A PROTOSTAR.
• STAGE 5: PROTOSTELLAR EVOLUTION.
• STAGE 6: A NEWBORN STAR.
• STAGE 7: THE MAIN SEQUENCE AT LAST.

At the end of a high-mass star’s fusion process, iron composes the star’s core. No nuclear fusion of iron is possible out of a high-mass star core, which has the same mass as our entire Sun. The pressure at the star’s iron-laden core continues to build until the ultimate cosmic fireworks occur: a supernova.

A star’s life expectancy depends on its mass. Generally, the more massive the star, the faster it burns up its fuel supply, and the shorter its life. The most massive stars can burn out and explode in a supernova after only a few million years of fusion.

R136a1

There are two possible stellar ending scenarios, depending on the star’s original mass. If the star is less than three solar masses, <3. M sun , this is the neutron star limit. If it is a single star ( not part of a binary star system), the star will eventually cool as a large cinder in space.

More massive stars have more weight pushing down on the core and higher temperatures in the core. This means more high energy hydrogen atoms having more collisions. Thus, fusion takes place more rapidly in larger stars and the fuel is used faster.

The classic low-mass star is the Sun. Low-mass stars have large convection zones when compared to intermediate- and high-mass stars. In very low-mass stars , the Convection Zone goes all the way to the star’s core! In about one billion years, the Sun will begin its Red Giant phase.

A main sequence star is powered by fusion of hydrogen into helium in its core. High-mass main sequence stars have shorter lifetimes than low-mass main sequence stars.

UY Scuti

A higher-mass star may have more material, but it burns through it faster due to higher core temperatures caused by greater gravitational forces. While the sun will spend about 10 billion years on the main sequence, a star 10 times as massive will stick around for only 20 million years.

Stars with masses between 2 and 8 solar masses.

According to current knowledge, yes. If the gas cloud is too massive, the pressure of the radiation prevents the collapse and the star formation. The article Stars Have a Size Limit by Michael Schirber, it’s about 150 Solar Masses.

On the main sequence, star sizes and colors are directly related. Larger stars are hotter and more massive than smaller stars.

Stellar mass is a phrase that is used by astronomers to describe the mass of a star. Hence, the bright star Sirius has around 2.02 M ☉. A star’s mass will vary over its lifetime as mass is lost with the stellar wind or ejected via pulsational behavior, or if additional mass is accreted, such as from a companion star.

For the fusion reactions to occur, though, the temperature in the star’s core must reach at least three million kelvins. And because core temperature rises with gravitational pressure, the star must have a minimum mass: about 75 times the mass of the planet Jupiter, or about 8 percent of the mass of our sun.

In astronomy, minimum mass is the lower-bound calculated mass of observed objects such as planets, stars and binary systems, nebulae, and black holes. It is likely that the smallest mass for a black hole is approximately the Planck mass (about 2.2×10−8 kg or 22 micrograms).

Stars like the Sun will probably lose about 45% of their initial mass and become white dwarfs with masses less than 1.4 MSun.

Supergiants are rare and short-lived stars, but their high luminosity means that there are many naked-eye examples, including some of the brightest stars in the sky.