Life Cycle of a Big Star

Stars are such a beautiful and amazing part of the Universe. Who doesn’t look up into the night’s sky and wonder about these little specks of light shining in the dark voids of space? Since the dawn of man, we’ve been observing, recording, plotting and exploring the stars and wonders in the sky.



Photo by Stuart Rankin,


Stars are such an important part of the Universe, stars of all sizes; small, average, big and even massive stars. If you’re interested in learning about the life cycle of average stars, this is a great resource to get started in this collection of articles about the life cycle of stars.

In this article, we’ll go into the details and the nitty-gritty of the life cycle of big stars, which are categorized as roughly 1.5 – 3 times the size of our Solar System’s star; the Sun.

The size of a star greatly influences the length of a star’s life. The bigger the star, the shorter the life, and of course, the opposite is true for smaller stars. The size of a star dictates how much and how quickly it will fuse its hydrogen to helium – and its helium to then carbon, and ultimately its carbon to iron.

While smaller stars (equal to or less than 1.5 times the size of our Sun) can live as long as; 2,000,000,000,000 and 2,000,000,000 years. For big stars (1.5 to 3 times the size of our Sun), they generally live between 2,000,000,000 and 200,000,000 years.



Photo by NASA Goddard Space Flight Center,


These big stars are also super hot, and I don’t mean sexy. I mean, they generate heat at unbelievable temperatures. For big stars (1.5 to 3 times the size of our Sun), they produce heat between 12,140 (7,000 Kelvin) and 19,340 (11,000 Kelvin) degrees Fahrenheit – wow!

The Life Cycle of a Big Star – Birth:

Just as with humans – it doesn’t matter what shape your body is, the color of your skin or what size you are; we all come from the same place – mommies and daddies.

Stars are no different. Stars of all shapes, colors and sizes come from the same place; Giant Molecular Clouds – the mommies and daddies of stars.



Photo by Don McCrady,


These giant molecular clouds are massive bodies of gas and dust and are very cold in temperature, ranging between -440 (10 Kelvin) to -370 (50 Kelvin) degrees Fahrenheit.

They are also big, very very big and stretch for 100 to even 600 light years in diameter. That’s the equivalent of 587,862,537,318,360 to 3,527,175,223,910,164 miles, in diameter.

Think about the size of giant molecular clouds like this; the Sun’s diameter is only 864,938 miles. You could fit between 679,658,585 and 4,077,951,510 Sun’s, side by side from one end of a giant molecular cloud to the other end. That’d be a lot of light and heat!



Photo by European Southern Observatory,


From the time a star is born, it morphs from a protostar to a main sequence star. A main sequence star is the phase of the life cycle of a star where it spends a majority of its life.

The Life Cycle of a Big Star – The Middle Years:

As a star enters the main sequence stage of its life, it spends a great deal of time doing one very simple, yet very complex thing; nuclear fusion.

Now, you might be asking yourself, what is nuclear fusion and why does a star spend millions and billions of years doing this? Well, good questions and you basically already know the answers.

Nuclear fusion is best known by an equation made famous by Albert Einstein; E=mc2. Plain and simple.

It spends so much time of its life fusing larger elements into smaller elements because of how big and how much of these elements stars contain.

What is Nuclear Fusion in a Nutshell?

Nuclear fusion takes place in the core of a star, where hydrogen atoms are converted into helium atoms. A positive hydrogen nuclei, ionized hydrogen atoms or protons slam together and release energy.



Photo by NASA Goddard Space Flight Center,


Larger elements collide and convert into smaller elements; the change in the size of these elements through the collision is the release of energy.

In the equation, E=mc2, E represents Energy, which is equal to the change in mass of the elements as represented by mc2, which is mass (M) multiplied by the Speed of Light (C), squared.



Photo by Image Editor,


During the main sequence phase of the life cycle of a big star, nuclear fusion is the process which gives a star its light and heat; two of the most critical components to a solar system and the building blocks in the recipe of life.

As a star converts its hydrogen to helium, it produces light and heat, over the course of time, it will run out of hydrogen to slam together to create helium atoms. When this balance of the elements begins to shift and less and less hydrogen is present; the star enters into the next phase of its life cycle as a big star; death.

The Life Cycle of a Big Star – The Golden Years:

Ahhhh, the golden years. The kids have left the nest, the mortgage is paid off or paid down, your days are freed up from retirement and all have left to do is to look forward to… death.

Ok, well, for a human that’s pretty terrible, but for a star – it’s pretty awesome! The death of star begins an exciting part of its life cycle, in fact, for big stars it’s one of the most amazing phenomenons in all of existence.



Photo by NASA’s Marshall Space Flight Center,


As we just saw, in the latter years of the life cycle of a big star, the hydrogen atoms have converted into helium atoms in the star’s core. As this process takes place, the star begins to expand and cool off.

The Red Supergiant Phase:

The red supergiant phase of a star’s life cycle is awesome. It’s when a star runs out of hydrogen and its core is mostly made of helium. This causes the star to increase in size and it becomes a supergiant… and also takes on a red coloring. Well, actually the red coloring refers to where the temperature of the star renders on the stellar spectral class of the Morgan–Keenan Classification.



Photo by Stuart Rankin,


As a star expands and cools, their core’s shrink – this is from the conversion of larger and lighter elements into smaller and heavier elements. In the next phase of the life cycle of a big star, the star will have converted all of its helium into carbon. This will take place over the course of 1 to 2 million years.



Photo by Penn State,


If our Sun was a red supergiant, the edge of the Sun would reach all the way beyond the current orbit of Mars, which is 139,433,710 Miles from the Sun.



“Redgiants” by Sakurambo at English Wikipedia – Transferred from en.wikipedia to Commons.. Licensed under Public Domain via Wikimedia Commons –


As the carbon elements increase in relation to the helium left over in the star, the carbon will begin the fusion process and the collisions will convert that element into a smaller, denser and even heavier element; iron.

The process of fusing carbon into iron elements can take place in as little as a few thousand years. This is where the next phase of the life cycle of a big star takes place and brings it one step closer to its death.

The Supernova Phase:

During this phase of the life cycle of a big star, the hydrogen has all but converted into helium, which took place over the course of millions and billions of years. The helium has converted into carbon, which took place over one to two million years. And now, the carbon is in the final process of fusing into iron, the heaviest and hottest element in the nuclear fusion process of a star.



Photo by Stuart Rankin,


Once the core of the star is filled with iron, it’s dense and hot, upwards of a 100 billion degrees. At this point, one of the most amazing events in the Universe takes place; a supernova.

The supernova is an explosion from the gravitational collapse of the red supergiant’s iron core. The collapse takes place over an instant and the shock waves blow the outer layers of the star into space.



Photo by NASA’s Marshall Space Flight Center,


The supernova is a sight for sore eyes, literally. This event illuminates the brightness equivalent of 100 million Suns, over a very short period of time. Supernovas that take place many light years away from Earth can be seen with the naked eye.

Supernova events are believed to be one of the main sources of elements found in the Universe heavier than hydrogen and helium. Pretty heavy, man!

The Neutron Star Phase:

After a red supergiant converts all of its core into iron and a massive gravitational collapse takes place and the star goes supernova, it becomes something extraordinary; a neutron star.

A neutron star is the most dense and smallest known star, they’re the result of a supernova and are nearly made up of entirely, you guessed it… neutrons!

At this point of the life cycle of a big star, the star is dead, kind of. Neutron stars, full of neutrons, are very hot still, have strong magnetic fields and spin very rapidly.



“Neutron star cross section” by Robert Schulze – Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons –


Most neutron stars are about 7 miles in radius and have the mass of roughly 2 of our Sun. To put that into perspective, our Sun’s radius is 432,450 miles. So imagine an object nearly 61,778 times smaller than our Sun, but 2 times its mass. Cray cray!

If you were to scoop up some pieces of a neutron star and put it in a standard size pack of gum or matchbox, it’d weigh approximately 5 trillion tons of Earth rock. Talk about a dense and heavy object!



“PIA18848-PSRB1509-58-ChandraXRay-WiseIR-20141023” by NASA/CXC/SAO (X-Ray); NASA/JPL-Caltech (Infrared) – Licensed under Public Domain via Wikimedia Commons –


Because neutron stars are so small, so dense and are full of neutrons, they spin and rotate at incredible speeds. Some neutron stars can spin 716 times per second (42,960 RPMs), that’s insane!

Think about that data point like this, if you’re traveling on the freeway your car’s engine likely makes a full rotation 41 to 50 times per second, when cruising between 2,500 and 3,000 RPMs. A neutron star is spinning nearly 15 times faster than your car’s engine on the freeway!

The first neutron star was discovered by Walter Baade and Fritz Zwicky, in 1934 – one year after the discovery of the neutron. The first neutron star discovered was RX J185635-3754 and can be seen in viable light.



“IsolatedNeutronStar” by Original uploader was Northgrove at en.wikipedia – Transferred from en.wikipedia. Licensed under Public Domain via Wikimedia Commons –


Now that a star went through its life and is now a neutron star, it’ll remain that way until forever. All is well, that ends well.



Featured image by NASA’s Marshall Space Flight Center,

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