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Transcript of Stellar Evolution
Brandon Reyes Stellar Evolution Stellar Evolution Introduction Massive stars Stellar Evolution :
The Birth, Life, and Death of a Star In massive stars, the core is already large enough at the onset of hydrogen burning shell that helium ignition will occur before electron degeneracy pressure has a chance to become prevalent. Thus, when these stars expand and cool, they do not brighten as much as lower mass stars; however, they were much brighter than lower mass stars to begin with, and are thus still brighter than the red giants formed from less massive stars. These stars are unlikely to survive as red super giants; instead they will destroy themselves as type II supernovas. The Milky Way Galaxy contains several hundred billion stars of all ages, sizes and masses. A typical star, such as the Sun, radiates small amounts of X-rays continuously and larger bursts of X-rays during a solar flare. The Sun and other stars shine as a result of nuclear reactions deep in their interiors. These reactions change light elements into heavier ones and release energy in the process. The outflow of energy from the central regions of the star provides the pressure necessary to keep the star from collapsing under its own weight. Stellar evolution is the process by which a star undergoes a sequence of radical changes during its lifetime. In other words its the birth and death of a star. All stars are born from collapsing clouds of gas and dust, often called nebulae or molecular clouds. Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what is known as a main sequence star. Stellar Evolution Introduction Schematic of stellar evolution Stars come in all different colors.
The color of a star indicates its surface temperature,
an important property used to assign each star a spectral type. Most stars in the above Sagittarius Star Cloud are orange or red and relatively faint, as our Sun would appear. The blue and greenish stars are hotter,
many being relatively young and massive.
The bright red stars are cool Red Giants,
bloated stars once similar to our
Sun that have entered a more advanced
stage of evolution. Alima Islam
Brandon Reyes Sagittarius Star Cloud A Sun's Life Cycle Birth & Death
of a Star Sun's Death (Its Effects) Fun Facts Quiz
1. What is the brightest star in our milky way?
a) North Star
b) The Sun
2. Which state of matter are stars mainly composed of?
a) helium gas
3. What is the sun primarily made of?
d) nuclear fusion
4. Stellar evolution is best described as a process in which:
a) stars expand across the universe
b) stars become constellations
c) stars undergo dramatic changes in their lifetime
d) stars undergo a transition from being stars to become satellite transmitters
5. What does the color of a star indicate?
a) where it's location is
b) what stage it's in during it's evolution process
c) what it's surface temperature is
d) what constellation it's from The Sun was born in a vast cloud of gas and dust around 5 billion years ago. Over time, this gas and dust began to fall into a common center under the force of its own gravity. Mass began to form and the Sun grew hotter and hotter until it reached 1 million degrees and causing its core to ignite and begin nuclear fusion. Our sun has the life span of 10 billion years
Stars are mainly composed of plasma
The brightest star in the milky way is named Sirius
Stars are composed of plasma as their state of matter
A star is born every 18 days in our galaxy
A person can see approximately 3000 stars on a clear night from a certain location
The oldest star found by man is HD140283
There are more stars than grains of sand on earth
All of the stars comprising the Milky Way galaxy revolve around the center of the galaxy once every 200 million years or so. Sources http://www.astronomytoday.com/cosmology/evol.html
http://www.quizmoz.com/quizzes/Universe-Quizzes/s/Stars-Quiz.asp Answers 1. c) Sirius
2. b) plasma
3. d) nuclear fusion
4. c) stars undergo dramatic changes in their lifetime
5. c) what it's surface temperature is The End ?? Questions ?