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Red Supergiant Stars

General Information

  1. The surfaces of all stars are made of pretty much the same things in the same amounts: by mass, 70% hydrogen, 28% helium, and 2% of everything else (note that hydrogen is the least massive).

  2. The insides of stars are different, depending on the type of star, and what stage of life the star is in.

  3. Red stars are cool stars.

  4. Red supergiant stars are no longer fusing hydrogen in their cores: most of the hydrogen has been converted into helium. So, red supergiant stars are no longer considered “main sequence” stars.

  5. As blue and yellow stars begin to die, they become larger and cooler. The supply of hydrogen in their cores has been exhausted. The core then collapses, heats up, then begins fusing helium into carbon. Meanwhile, a layer of hydrogen has remained around the core. This hydrogen continues fusing, and the energy produced expands the outer layers of the star. So, red supergiant stars are very, very large stars. Because they’ve expanded, the surfaces of red supergiant stars are cool.

  6. The red supergiant phase of the star ends when there is no nuclear fuel remaining in the star’s core. At that point the core fully collapses. The layers immediately above the core also collapse, rebound when they reach the collapsed core, and rip the outer layers of the star apart in a supernova explosion. Often, a black hole or a neutron star (pulsar) is left after the explosion.

  7. Neutron stars and black holes contain much more matter than our sun, but are the size of a city, or smaller! (Consider: the sun has 333,400 times more matter than Earth!) The material in a neutron star is so densely packed, it does not resemble matter we’re familiar with on Earth. A black hole’s mass is confined to such a small volume that if something gets too close to it, it cannot go fast enough to escape (not even light can go fast enough if it passes by to closely).

  8. The sun is not massive enough to go through this process when it dies. When it dies it will become a red giant, gently puff off its outer layers, and form a planetary nebula and white dwarf.

  9. Although these stars are referred to as red super giants, their color can be red, orange, or yellow.
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