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Las 3.3 - Stellar Evolution

The document outlines the life cycle of stars, beginning with the formation of a protostar from a collapsing nebula due to gravity. It describes the progression from main sequence stars to red giants, and the eventual outcomes for medium-size stars (white dwarf and black dwarf) and massive stars (supernova, neutron star, and black hole). The document also includes questions for students to complete the life cycles of medium-size and massive stars.

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7 views1 page

Las 3.3 - Stellar Evolution

The document outlines the life cycle of stars, beginning with the formation of a protostar from a collapsing nebula due to gravity. It describes the progression from main sequence stars to red giants, and the eventual outcomes for medium-size stars (white dwarf and black dwarf) and massive stars (supernova, neutron star, and black hole). The document also includes questions for students to complete the life cycles of medium-size and massive stars.

Uploaded by

mynsntlln1212
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as DOCX, PDF, TXT or read online on Scribd
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NAME: ________________________________ DATE: _____________________

GRADE & SECTION: ___________________ SCORE: ____________________

LEARNING ACTIVITY SHEET # 3.2


STELLAR EVOLUTION (LIFE AND DEATH OF STARS)

Objective: To describe the life cycle of stars

Stellar evolution started minutes after the Big Bang explosion. A vast cloud of gas and dust called nebula starts to
collapse due to the action of gravity. Gravity pulled the clouds together creating a protostar. A protostar is an early stage
in the evolution of a star, after the beginning of the collapse of the gas cloud from which it is formed, but before sufficient
contraction has occurred to permit initiation of nuclear reaction at its core.
As the protostar becomes denser and denser, it forms a main sequence star. Main sequence stars are composed
primarily of hydrogen. The first fusion process occurs at the hydrogen core of stars with the temperature of less than 15
million Kelvin.
As more hydrogen and hydrogen is burned into helium, the core of stars become comprised with helium as
hydrogen is depleted. The star has a very dense helium core and a hydrogen shell. Temperature and density increases up
to 100 million Kelvin. The stars thermal pressure cause it to push the gas and the star balloons into a red giant. As the star
becomes older, it becomes a red giant. Red giant stars used up its energy and becomes cooler so it expands.
Because of the increase in temperature, several nuclear fusion process will occur in red giant aside from hydrogen
fusion.
Stars keep growing as it accumulates mass up to the point where the stars will eventually be unable to generate
energy to push against gravity due to the formation of heavier elements.
Stars collapse. For medium-size stars like our sun, layers of the red giant fall off, releasing dust and gas into
space. It is called planetary nebula. The remaining star is very dense and bright. It is called a white dwarf. When a
white dwarf stops glowing, it is called a black dwarf.
Massive stars are different. When they die, they make a supernova – a giant explosion. After the explosion, the
star becomes either a neutron star or a black hole. Neutron star is a white dwarf that has very high pressure and
temperature. Black hole is a neutron star with gravity so strong that nothing, even light can escape.

ANSWER THE FOLLOWING QUESTIONS:

A. Complete the life cycle of medium-size stars:

Nebula  Protostar  _______________________  Red giant  ____________  black dwarf

B. Complete the life cycle of massive stars:

Nebula  Protostar  ______________________  Super red giant  ________________  ____________

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