Life Cycle of Stars

Constellation Project

Information

How Stars Begin…

• Inside vast clouds of gas and dust floating in space, gravity causes the denser areas to pull together, or coalesce.

• These clouds are called nebulae.

Crab Nebula

Cat’s Eye Nebula

As the nebula starts to spin…

• Gravity compresses the gas and dust into a spinning disk with a bulge in the middle.

• A warm protostar forms as the center collapses under its own gravity.

• The protostar radiates heat and ejects matter from its poles.

• Eventually, fusion begins in hydrogen gas at the core and the star begins its life.

The disk either disperses or forms planets

Not all stars are the same:

• Stars exist that are significantly larger and significantly smaller than our sun.

• Not all stars have planets.

• Some stars are older than our sun and some are younger.

The Hertzprung-Russell Diagram

• Built to show the relationship between absolute magnitude, luminosity, classification and effective temperature of the stars.

Many variations exist..

• Notice the spectral classes at the bottom and their relationship to surface temperature.

• This version also includes the red and blue giant regions.

• Be sure to compare your stars to the Sun.

How Stars End

• Stars burn until they use all their nuclear fuel.

• Different size stars evolve differently.

• The larger a star, the hotter, brighter and shorter lived it is.

A Star the Size of Our Sun

• Burns for 10 billion years

• Star exhausts its hydrogen and swells into a red giant.

• Core collapses. Nuclear reaction blows off the star’s surface.

Blown-off gases form a glowing nebula.

The core of the star collapses into a white dwarf star.

• When our Sun becomes a red giant its size will interfere with the Earth’s orbit.

• We’re about 4 billion years from when that will occur.

A Star 10 x the size of our Sun

• Burns out in 20 million years

• Bright, hot, blue star uses up its hydrogen fuel, swells into a red supergiant.

• It is 5000 x more luminous than our Sun (see comparison in the two pictures)

• When nuclear reactions cease, the core collapses and the star explodes in a brilliant supernova.

• If the star explodes with enough force, much of its mass is hurled into space, leaving behind a small, dense neutron star.

A Star 30 x the size of the Sun

• These stars can exhaust their fuel in as little as 1 million years.

• This large star is one of the most luminous in the universe.

• It expands into a red supergiant and ends in a powerful supernova explosion.

• Its huge core collapses past the neutron star stage and becomes a black hole

• This is a dense, heavy structure whose gravity is so strong that not even light can escape from the interior.

An artists representation

• I love this picture of a black hole seemingly devouring a nearby star.

• Notice the X-ray emissions of the black hole showing how matter is changed into energy.

Works Cited

• Rand McNally New Concise Atlas of the

Universe, “The Universe Explained;

The Life and Death of Stars”