STAR LIFE CYCLES A stars color and brightness

STAR LIFE CYCLES

A star’s color and brightness depends on the stage in it’s life, and the elements that are present.

1)Stellar Nursery--Nebula Space is filled with the stuff to make stars (gas, dust, small chunks of matter, and basic elements like H, He, C, Si, etc.

2)Collapse to Protostar Stars begin with slow accumulation of gas and dust. • Gravitational attraction of Clumps attracts more material. • Contraction causes Temperature and Pressure to slowly increase. • At 15 million degrees Celsius in the center of the star, fusion ignites ! • Colors are normally white to blue

3) A Balancing Act– MAIN SEQUENCE Energy released from nuclear fusion (push) counter-acts inward force of gravity (pull)= HYDROSTATIC EQUILIBRIUM. Throughout its life, these two forces determine the stages of a star’s life. The star is now in “Main Sequence”, and is yellow or white.

3 S) Small mass stars shrink down after this to a lump of charcoal. . BLACK DWARF • Once a smaller main sequence starts to shrink and cool, it becomes a nonilluminated piece of dark matter floating in space.

4)The Beginning of the End: Red Giants After Hydrogen is depleted in core. . . Energy released from nuclear fusion is not as strong as the force of gravity. • Core collapses… · Collapse converted into heat and pressure. · This heat expands the outer layers (like a blister from a skin irritation)

A Red Giant You Might Know

5 M)The end for medium stars When a red giant starts to cool, the “skin” stays intact, but The matter underneath shrinks towards the center =Planetary Nebula

6 M) White dwarfs At center of Planetary Nebula lies a White Dwarf. • Density of the size of the Earth with Mass of the Sun : “A ton per teaspoon” • It wants to collapse further, but electrons are keeping it from doing so. • White dwarfs can cool/condense to form black dwarfs later.

5 L) Red Giant to SUPERGIANT A red giant will continue to collapse internally, but swell externally into a RED SUPERGIANT. This is because larger stars can make more heavy elements from fusion!

6 L) Supernova ! An explosion as a result of an implosion of heavy matter made during fusion

Supernova Remnants: Cas A Optical X-ray

Elements from Supernovae All X-ray Energies Calcium Silicon Iron

7 L) What’s Left After the Supernova Neutron Star (If mass of core < 5 x Sun) • Under collapse, protons and electrons combine to form neutrons. • 10 Km across Black Hole (If mass of core > 5 x sun) • A vacuum so strong, not even light can escape… usually you can only see them because they are “sucking” radiation from normal stars!

Let’s review. . . Which stages does a small star not have? Why?