The "Fingerprints" of Stars The best tool we have for studying a star's light is the star's spectrum. A spectrum (the plural is "spectra") of a star is like the star's fingerprint. Just like each person has unique fingerprints, each star has a unique spectrum. Spectra can be used to tell two stars apart, but spectra can also show what two stars have in common. The spectrum of a star is similar to the spectrum of colors you see in rainbows. Stars give off light in a range of different colors. The spectrum of visible light - the spectrum you see in a rainbow - is shown below.

Life Cycle of Stars

Cat’s Eye Nebula

Nebula Giant cloud of Gas and Dust

Protostar – the force of gravity pulls hydrogen gas together and it begins to spin

Main Sequence Hydrogen in the core is converted into Helium by nuclear fusion Once fusion occurs, the star begins to shine or glow Hydrogen + Hydrogen = Helium + lots of energy

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Red Giants All the hydrogen has fused to helium. The Helium in the core of the star is still burning hot. Helium starts fusing together to create Carbon or Oxygen.Gravity keeps contracting the core to maintain equilibrium, and as the core contracts the atoms are packed together even tighter than before. The outer shell has expanded in an effort to help heat from the core escape into space. The red giant is the first step in old age.

Red Giant Hydrogen in core begins to run out Core becomes unstable and contracts Outer core expands Cools and glows red

Aldebaran is a K5III star, which means it is orangish, large, and has moved off the main sequence after exhausting the hydrogen fuel in its core. It has a minor companion (a dim M2 dwarf orbiting at several hundred AU). Now primarily fusing helium, the main star has expanded to a diameter of 44.2 times the diameter of the Sun,main sequencehydrogen AUheliumSun

Length of life of star is determined by MASS

Low to medium mass star A low to medium mass star will become a white dwarf

White Dwarf Last of the helium atoms in core are fused into carbon atoms Star begins to die Star collapses and is extremely dense Ultraviolet light makes the material glow

Black Dwarf Once energy is gone, the star will no longer emit light. The star will remain like this forever

Massive stars After the red giant phase, a massive star will undergo a supernova explosion.supernova explosion Supernova explosion - a release of energy when fusion of the atoms stop

Supernovas

If the remnant of the explosion is 1.4 to about 3 times as massive as our Sun, it will become a neutron star.neutron star

Pulsar Is a Rotating Neutron Star

If more massive than 8 times the mass of the sun Gravity finally wins and compresses everything to a mathematical point at the center. The point mass is a black hole. Only the most massive, very rare stars (greater than 10 solar masses) will form a black hole when they die

Red Supergiant star – Massive, will become a black hole someday!!

STAR FORMATION Gravity causes clouds of gas and dust (nebula) to contract until nuclear fusion of light elements into heavy ones occur Once fusion occurs, the star glows

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