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Life Cycle of a Star

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nathalia holguin

on 24 August 2016

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Transcript of Life Cycle of a Star

Life Cycle of a Star
Color of a star
New stars come in a variety of sizes and colors. Range from blue to red, from less than half the size of our Sun to over 20 times the Sun's size.
Color of star depends on the surface temperature of the star.
The more mass a star starts out with, the brighter and hotter it will be.
The hottest stars are blue and the coolest stars are red.
Nuclear fusion
An atomic reaction that fuels stars.
Stars are powered by nuclear fusion in their cores, mostly converting hydrogen into helium.
Death of a star

Main sequnce star burns through the hydrogen in its core, reaching an end of its cycle.
The life span of a star depends on the mass.
Stars about the same size of the sun will live for many billions of years and then die relatively quietly.
Stars that are much more massive only live for only a few million years and end their liver violently.
Stars are born in the billowing clouds of gas and dust.
Dust nebulae that exist in the seemingly empty space between the stars.
Star formation beings in the densest and coolest regions of dark nebulae in what are called giant molecular clouds
By: Sunee Thoedpraiphanawan & Natalia Holguin
Star Birth
Main Sequence
Diagonal region of the Hertzsprung Russell diagram in which most stars are located, generally these are stable stars during the bulk of their lives.
Stars that are fusing hydrogen atoms to form helium atoms in their cores.
Most stars in universe about 90% of them are main sequence stars.
Sun is a main sequence star. Stars can range from about a tenth of the mass of the sun to up to 200 times as massive.
Protostar
Large mass that forms by contraction out of the gas of a giant molecular in the interstellar medium.
Protostar is birth of a star. They're stars that are starting out in their life as a star. Don't get very warm, and are pretty cool for star's temperature.
HR diagram
A plot of absolute magnitude versus spectral type (or temperature) for group of stars.
Scales are not linear. Hot stars inhabit the left hand side of diagram. Cool stars the right hand side. Bright stars at the top, faint stars at the bottom. Sun is fairly average star and sits near the middle.
It shows that the temperature coincides with the luminosity, the hotter the star the higher the luminosity the star has.
You can also tell the size of each star from the graph as the higher the radius the higher the temperature and luminosity.
Nebula
Stars are born by contraction of gasses inside a nebula.
Nebula is a cloud of interstellar dusts and gasses.
Every nebula comes in a different type of color or group of colors that owe to the type of energy sources that lights them or power them.
Usually gasses inside a nebula are a place that new born stars are developed and found.
Black Holes
They are very mysterious and amazing celestial objects that are the last part of the life cycle of a star.
If form near a star, it will swallow the star.
If is further away, might cause the star to wobble.
They form differently then other stars do. Black holes are the ending points of stars 10-15 times as massive as the Sun.
Supernovas
A super nova is a stellar explosion that is more energetic, than a nova.
Super Novas are extremely luminous cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months.
Binary stars
Binary star are two stars orbiting a common center mass. The brighter star is officially classified as the primary star, while dimmer of the two is the secondary (classified as A & B respectively.
Binary pairs classified based on their orbit.
Wide binaries - stars that have orbits which keep them spread apart from one another.
Close binaries - Evolve nearby, able to transfer their mass from one to the other.
Visual binaries - Two stars with wide enough separation that both can be view through telescope.
Cepheid variable and RR lynae variable
Cepheid variable stars distance indicators.
Certain stars that have used up their main supply of hydrogen fuel are unstable and pulsate.
RR Lyrae is a special star that changes in brightness with a regular period of a few days.
RR Lyrae variable is a type of variable star with a period of less than one day, common in globular clusters and used, like Cepheid variables, to measure galactic distances.
Luminosity
Luminosity of a star is the amount of light it emits from its surface.
Luminosity of a star depends on both its temperature and its radous (surface area).
A hotter star is more luminous than a cooler one of the same radius.
Bigger star is more luminous than a smaller one of the same temperature.
Apogee
The point in the orbit of the moon or a satellite at which it is furthest from the earth.

Stage of stars
Small star
Stage 1 - Stars born in region of high density Nebula, condenses into huge globule of gas and dust and contracts under its own gravity.
Stage 2 - Region of ondensing matter will begin to heat up and start grow forming Protostars. If protostar contains enough matter, central temperature reaches 15 million degree centigrade.
Stage 3 - At temperature, nuclear reactions n which hydrogen fuses to form helium can start.
Stage 4 - Star begins release energy, stopping it from contracting even more and causes it to shine. Now a main sequence star.
Stage 5 - A star of one solar mass remins in main sequence for about 10 billion years, untill all of the hydrogen has fused to form helium.
Stage 6 - The helium core now starts to contrast further and reactions begin to occur in a shell around the core.
Stage 7 - Core is hot enough for helium to fuse to form carbon. Outer layers begin to expand, cool and shine less brightly. Expanding star is now called Red Giant.
Stage 8 - Helium core runs out, and the other layers drift of away from core as a gaseous shell, this gas that surrounds the core is called Planetary Nebula.
Stage 9 - Remaining core (80% of original star) is now in its final stages. Core becomes White Dwarf star eventually cools and dims. When it stops shining, now dead star is called Black Dwarf.
Massive star
Stage 1 - Massive stars evolve in a similar way to a small stars until it reaches its main sequence stage.
Stage 2 - The massive star then become a Red Supergiant and starts of with a helium core surrounded by a shell of cooling, expanding gas.
Stage 3 - In the next million years a series of nuclear reactions occur forming different elements in shells around the iron core.
Stage 4 - The core collapses in less than a second, causing an explosion called a Supernobva, in which a shock wave blows of the outer layers of the star.
Stage 5 - Sometimes the core survives the explosion. If the surviving core is between 1.5 - 3 solar masses it contracts to become a tiny, very dense Neutron Star. If the core is much greater than 3 solar masses, the core contracts to become a Black Hole.
Neutron star
A star that has collapsed under its own gravity.
Created when giant stars die in supernovas and their cores collapse with the protons and electrons essentially melting into each other to form neutrons.
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