Presentation on theme: "Massive Stars live shorter lives. Low mass stars live longest. 1.Gravity contracts the Hydrogen gas 2. Gas Spins 3. Gas Heats 4. Protostar Stage 5. Fusion."— Presentation transcript:
Massive Stars live shorter lives. Low mass stars live longest. 1.Gravity contracts the Hydrogen gas 2. Gas Spins 3. Gas Heats 4. Protostar Stage 5. Fusion begins in the clouds core 6. Cloud glows brightly 7. Main Sequence Star A Stars Lifespan depends on its Mass
Hydrogen collects in the center of the swirling disk. The cloud begins to shine brightly, a young star is born in the cloud Gravity pulls the densest pockets of hydrogen gas inward The Gas spins faster, and heats up.
Sun Like Star – Long Lifetime The protostar is now a stable main sequence star.main sequence star Gravity pulls in – Pressure pushes out Star is in balance Neither shrinks or expands Yellow shining mass
The Sun is a Main Sequence Star It fuses hydrogen gas into helium Lifetime: 10 billion years. Near the end - hydrogen fuel is depleted and the star begins to die.begins to die Our Sun is considered to be an ordinary star with a spectral classification of G2 V, a yellow dwarf main sequence star.
Sun Like Stars how do they do it? In the star’s core protons collide and stick together with a strong nuclear bond. A chain reaction occurs, 4 protons weld together to make 2 protons & 2 neutrons. Hydrogen converts to Helium through nuclear fusion. Every second the Sun through thermonuclear reaction converts 600 million tons of hydrogen into Helium within its core and emits a tiny fraction of energy E=MC 2, the radiation escapes into space bathing the star’s surroundings in heat and light. This is what warms our solar system
As the Sun ages, Eventually, the Supply of hydrogen in the core ends, and a shell of hydrogen surrounds the helium core. The Sun’s core becomes unstable The helium core contracts and gets hotter.
Red Giant star seen from a planet The Sun’s hydrogen shell expands The Sun is now a Red Giant Hydrogen in the shell around the core continues to burn Its core temp continues to increase
Red Giant Phase Now the Helium core contracts When the Hydrogen shell ignites: The shell continues to push outward Sun becomes enormous It goes from 1 million to 100 million miles in size
Helium ignites, it starts to fuse into Carbon and Oxygen. The core collapses. The outer layers are expelled. It becomes a brilliant cool variable star for thousands of years like Betelgeuse in Orion. Actual photograph of Betelgeuse
Eventually all of the hydrogen gas in the outer shell of the Red Giant is blown away by stellar winds to form a ring around the core. This ring is called a planetary nebula. The core is now a hot white dwarf star. A white dwarf star is left in the center of the dying red giant star, surrounded by the red giant’s expanded atmosphere
A White dwarf star is a dense stable star about the size of the Earth weighing three tons per cubic centimeter. It radiates its left-over heat for billions of years. When its heat is all dispersed, it will be a cold, dark black dwarf - essentially a dead star
When massive stars ( At least 5 times larger than the Sun) reach the red giant phase, their core temperature increases because carbon is formed from the fusion of helium. Gravity pulls carbon atoms together. The core temp goes higher forming oxygen, then nitrogen, and eventually iron.
The core becomes iron, fusion stops. No energy. Iron is the most stable element and requires the most energy of any element to fuse. So, the core heats to 100 billion degrees, the sudden lose of energy causes the core to collapse The iron atoms in the core are crushed. The core becomes rigid. In falling layers of the star strike the core, then recoil in a Shockwave. The shockwave hits the surface and the star explodes.
If the core of a massive star collapses when it is 1.5 to 3 times as massive as our Sun’s core. It ends up as a neutron star. The protons and electrons are squeezed together by gravity, leaving a residue of neutrons, creating a neutron star. Neutron stars (right) are about ten miles in diameter. Spin very rapidly (one revolution takes mere seconds!). Neutron stars are fascinating because they are the densest objects known except for black holes. A teaspoon of neutron star material weighs 100 million tons.
Massive Stars (8 times or more larger than the Sun. Core remains massive after the supernova. Fusion is stopped. Nothing supports the core. The core is swallowed by its gravity. It becomes a black hole Black holes are detected by X- rays given off matter that falls into the black hole.