Red Dwarf Stars - Introduction
Brief Description and Lifecycle
Red Dwarf stars make up 50% of the stars in space, and yet there is not a
single Red Dwarf star that is visible to the naked eye from the northern hemisphere.
These little stars have a simple lifecycle, but at least they collapse and reach
the HR Diagram ... something that their smaller cousin Brown Dwarfs never do.
They are small balls of gas and dust with a mass somewhere between 0.08 and
0.5 solar masses (remember that one solar mass is the mass of our own Sun, which
is 1.989X10^30 kg). These objects will collapse and generate sufficient internal
pressures to raise the temperature to the critical fusion point of 7 million
K. At this temperature, hydrogen gas is fused into helium, gamma radiation is
created, and the object becomes an official star! While they are stars, they
burn at a very slow rate, and thus they produce significantly less energy that
our Sun. the surface temperature of these stars is near 3000K, and thus their
corresponding color is red. Being small, they are called Red Dwarfs. It is interesting
to note that they have less than half the mass of the Sun, but because they
burn their hydrogen fuel so slowly, they will most definitely outlive our own
Sun. In fact, these objects are theorized to live 20 - 100 billion years or
longer, and thus is is probable that many of the red dwarf stars we see with
a telescope might be as old as the Universe. When their core supply of hydrogen
is exhausted, the core will collpase a bit, but never enough to ignite fusion
of helium into anything else. The object simply moves off the HR Diagram Main
Sequence, becomes a White Dwarf that will slowly cools into a Black Dwarf.
Starting Mass - 0.08 to 0.5 solar masses
General Length of Life - 20 billion years and longer
General Lifecycle - 1) gravitational collapse of a gas cloud into a protostar;
2) ignition of hydrogen --> helium fusion; 3) core fuel exhaustion; 4) collapse
into a White Dwarf, but never able to convert helium into anything else.
Final Life Stage - a cold ball of helium gas
To learn more about these relatively mundane objects, go to the Red
Dwarfs page.