Massive Star: Definition, Facts & Life Cycle

Lesson Transcript
Instructor: Katie Chamberlain

Katie has a PhD in Microbiology and has experience preparing online education content in Biology and Earth Science.

A massive star is seen as such if it's at least eight times larger than the sun. Explore the definition of a massive star and facts about its life cycle including its main life sequence, leaving its main life sequence and its death. Updated: 09/10/2021

Beginning of a Massive Star

Any star which is larger than eight solar masses during its regular main sequence lifetime is considered a massive star. They typically have a quick main sequence phase, a short red supergiant phase, and a spectacular death via a supernova explosion.

Massive stars are born, just like average stars, out of clouds of dust called nebulae. When a nebula collects enough mass, it begins to collapse under its own gravity. The internal pressure created by this collapse is enough to trigger fusion of hydrogen deep in its core. When nuclear fusion begins, a star is born. If the cloud of dust is large, it will create a massive star. A star is considered massive if it is at least eight times more massive than our Sun!

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  • 0:00 Beginning of a Massive Star
  • 0:48 Main Life Sequence
  • 1:37 Leaving Main Life Sequence
  • 2:38 Death
  • 3:05 Lesson Summary
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VX Sagittarii is a massive star.
VX Sagittarii is a massive star

Main Life Sequence

In all stars, hydrogen continues to be fused into helium during a stable portion of the star's life cycle called the main sequence. During this time, there is a balance between the gravitational inward forces and the core nuclear fusion outward forces. Until the hydrogen in the core is exhausted, the star will exist quite stably (although it probably would not make a good vacation spot).

The temperature, luminosity, and amount of time that it takes a star to expend its hydrogen are dependent upon its mass. A massive star will burn at an extremely high temperature; it will be beautifully luminous, but its hydrogen will only last for millions of years. This may seem like a long time, but it is like a blink of the eye in comparison to smaller stars that will exist for billions of years.

Leaving Main Life Sequence

When a massive star has expended all of its core hydrogen, this means that the gravitational forces pushing inward will overcome the fusion forces which had been pushing outward. The outer layers of the star will then compact inwards. In massive stars, the increased pressure in the contracting star can cause the latent hydrogen in the shell of the star and the helium in the core to begin fusing.

When these events happen, the outermost layers of the star are pushed out and the star swells up into a red supergiant star (or a blue supergiant star en route to a red supergiant). The constellation Orion has two of the most famous massive stars: Rigel and Betelgeuse.

The constellation Orion conatins two massive stars: Betelgeuse and Rigel.
The Constellation Orion

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