The Engines of our Universe Stars The Engines of our Universe

Life Cycle of Stars The Path a star takes over the course of its lifetime depends solely on its Mass!! Life Cycle of Stars The path a star takes over its lifetime depends solely on its MASS!!

Stellar Nursery - NEBULA All stars begin their lives in a NEBULA. NEBULAE are giant clouds of gas and dust. If there is enough matter in the cloud gravity will begin pulling together matter and begin spinning it inwards towards the center of the cloud.

PROTOSTARS Once enough matter has accumulated at the center point of gravity a PROTOSTAR will emerge. At this center, forces of gravity and pressure act on the collecting matter, heating it up and eventually causing FUSION to occur. https://www.khanacademy.org/partner-content/big-history-project/stars-and-elements/how-were-stars-formed/v/bhp-stars-light-up

FUSION Stellar FUSION is the process of lighter elements (Hydrogen) coming together to form heavier elements (Helium). FUSION is the engine that drives stars creating the energy and light that we feel as heat. Once FUSION occurs, the Star is born!

Life Cycle of Stars The Path a star takes over the course of its lifetime depends solely on its Mass!! Life Cycle of Stars The path a star takes over its lifetime depends solely on its MASS!!

MAIN SEQUENCE STARS Once born, most stars enter what is known as the MAIN SEQUENCE. Stars spend most of their life in the MAIN SEQUENCE. Stars continue to burn hydrogen and fuse helium throughout this phase. The duration of the MAIN SEQUENCE is directly proportional to the star’s mass.

Star Size and Color In addition to MAIN SEQUENCE duration, a star’s mass also determines its size and color. Star Mass = Pressure Pressure = Heat/Temperature Heat/Temperature = Color

Hertz-Russell Diagram

Sol (The Name of our sun) But where does our sun fit in??? Our Sun is a great example of a MAIN SEQUENCE star in the middle of its life (4.5 billion years old.) Our sun is about 5778 K and therefore a yellow star.

Life Cycle of Stars The Path a star takes over the course of its lifetime depends solely on its Mass!! Life Cycle of Stars The path a star takes over its lifetime depends solely on its MASS!!

RED GIANT As an average, MAIN SEQUENCE star gets older and larger, it becomes a RED GIANT. A star’s MAIN SEQUENCE ends when nearly all the hydrogen in the core has been fused. The RED GIANT’S core will transition from hydrogen to helium during this phase. The change in gravity at the core is what causes the star to expand.

DOUBLE-SHELL RED GIANT When the star’s hydrogen is exhausted, FUSION can no longer continue. The star’s core begins to contract due to its own gravity. Residual hydrogen then forms a zone outside the helium core where hydrogen FUSION resumes in a shell around the core. We call this a DOUBLE-SHELL RED GIANT.

RED GIANT During the RED GIANT phase energy produced in the burning shell of the star is spread over a much larger surface area. This results in a lower surface temperature changing the star’s color to red. Once FUSION in the star’s core raises the temperature hot enough to fuse carbon the RED GIANT stage comes to an end.

http://www.universetoday.com/122807/why-do-red-giants-expand/

PLANETARY NEBULA When the RED GIANT phase ends, INTERMEDIEATE-MASS stars blow out the outer shell layers hydrogen and helium forming what astronomers call a PLANETARY NEBULA. S

Potential elements FUSED in a HELIUM FLASH

Life Cycle of Stars The Path a star takes over the course of its lifetime depends solely on its Mass!! Life Cycle of Stars The path a star takes over its lifetime depends solely on its MASS!!

WHITE DWARF When the RED GIANT phase ends, a fused carbon core remains in the center of the PLANETARY NEBULA. The star’s core is now a collapsed down, very dense star called a WHITE DWARF. At the center of a WHITE DWARF’S is a massive sphere of carbon.

WHITE DWARF A WHITE DWARF’S faint luminosity comes from the emission of stored thermal energy. No fusion takes place inside a WHITE DWARF.

BLACK DWARF When a WHITE DWARF has radiated all of its thermal energy into space it becomes a BLACK DWARF. This means that its radiation, which initially has a high color temperature, will lessen and redden with time. Over a very long time, a white dwarf will cool and its material will begin to crystallize (starting with the core).

Life Cycle of Stars The Path a star takes over the course of its lifetime depends solely on its Mass!! Life Cycle of Stars The path a star takes over its lifetime depends solely on its MASS!!

MASSIVE STARS MASSIVE STARS are much hotter and brighter than MAIN SEQUENCE STARS. Most MASSIVE STARS begin life as blue-white stars within the MAIN SEQUENCE. Other MASSIVE STARS however will become what are known as BLUE GIANTS and SUPER-BLUE GIANTS.

MASSIVE RED GIANTS When HIGH-MASS STARS get older they become the largest stars in the universe known as MASSIVE RED GIANTS. These stars are similar to RED GIANTS except bigger and much hotter at their core. SUPER-HIGH MASS STARS in this stage are what is know as SUPER-MASSIVE RED GIANTS.

MULTI-SHELL BURNING RED GIANT

Elements FUSED in a MASSIVE RED GIANT

SUPERNOVA Eventually all HIGH-MASS STARS will die in an explosion known as a SUPERNOVA. SUPERNOVAS expel most of its stellar material away from the exploding star. This explosion drives a shock wave into the surrounding space.

SUPERNOVA SUPERNOVAS light up the skies for weeks even months after they explode.. Most will briefly outshine their own galaxy when they occur.

SUPERNOVA After a SUPERNOVA, HIGH-MASS STARS will become NEUTRON STARS. SUPER-HIGH MASS STARS will explode in a HYPERNOVA and become BLACK HOLES.

NEUTRON STAR All the left over matter after a HIGH-MASS SUPERNOVA condenses into a super-dense white core smaller than our earth called a NEUTRON STAR. These stars are extremely dense, hot and have tremendous pools gravity.

PULSAR Most NEUTRON STARS also emit pulses of gamma ray radiation at their poles called PULSARS. PULSARS can be seen from Earth using special Gamma Ray Telescopes.

BLACK HOLE SUPER HIGH-MASS STARS have so much mass that after a SUPERNOVA, the leftover material collapses in on itself creating the phenomenon known as a BLACK HOLE. Gravity is so strong in a BLACK HOLE that not even light can escape it!