LET’S EXPLORE OUR

UNIVERSE!

LET’S EXPLORE OUR

UNIVERSE!

STARSSTARS

QUESTIONS

• What is it about stars that made them the object of man’s fascination?

• What roles do they play in our lives?

• How much do we really know about them?

“Ancient civilizations searched the heavens in wonder and awe.”

ZIGURRAT

PYRAMIDS

STONEHENGE

“Watching the movement of the sun, moon and stars became a way to identify cycles for crop planting &

harvesting, celebrating events and marking the passage of time and seasons.”

“Watching the movement of the sun, moon and stars became a way to identify cycles for crop planting &

harvesting, celebrating events and marking the passage of time and seasons.”

CROP PLANTING

HARVEST

“And yet for some, it became a way of worship and seeking their unknown gods.”

“And yet for some, it became a way of worship and seeking their unknown gods.”

STARS, SUN AND MOON WORSHIP

ASTROLOGY

“But then again, we know far better to worship not the creation

but the Creator!”

“But then again, we know far better to worship not the creation

but the Creator!”

1“In the beginning God created the heavens and the earth... 3And God said, “Let there be light.” 4God saw that the light was good, and He separated the light from darkness. 5aGod called the light “day” and the darkness He called “night”…

14And God said, “Let there be lights in the expanse of the sky to separate the day from the night, and let them serve as signs to mark seasons and days and years, 15and let them be lights in the expanse of the sky to give light to the earth.” And it was so. 16God made two great lights – the greater light to govern the day and the lesser light to govern the

night. He also made the stars. 17God set them in the expanse of the sky to give light on earth, 18to govern the day and night and to separate light from darkness. And

God saw that it was good.”

GENESIS 1: 1,3-5a,14-18

QUESTIONS

• How are stars formed?

• How are they classified?

• What are the stages in the life of a star?

ORIGIN OF THE STARS

ORIGIN OF THE STARS

Stars originate from swirling clouds of gas in deep space located between other stars called the nebulae

Mutual gravitational attraction begins to pull particles from the gases into a cluster. The cloud of gas begins to condense eventually forming a

dense sphere called, protostar which a has an average diameter of 2.5 million kilometers.

Pressure and energy from hot gases due to the increasing fusion reaction begins to balance the gravitational attraction of each particle and a

newborn average star begins its stable life.

• Core – a dense, gaseous and very hot region where radioactivity take place.

Structure of an Average Star

Radiation zoneRadiation zone

CoreCore

Convection zoneConvection zone

• Radiation zone – the region where energy in the form of radioactive particles is absorbed and reemitted.

• Convection zone – the region where gases that are heated by the radiation zone rises to the surface and emit energy in the form of visible light, ultraviolet and infrared radiation which moves out into space.

CLASSIFICATION OF STARS

CLASSIFICATION OF STARS

ACCORDING TO BRIGHTNESS AND TEMPERATURE

Factors that Affect the Brightness of Stars

1. The amount of light produced by the star

2. The size of the star

3. The relative distance of the star

STAR TYPES AND THEIR TEMPERATURE

Type Color Temperature (in K)

O Bluish 30 000 – 80 000

B Bluish 10 000 – 30 000

A Bluish 7 500 – 10 000

F White 6 000 – 7 500

G Yellow 5 000 – 6 000

K Red orange 3 500 – 5 000

M Reddish 2 000 – 3 500

STAGES IN THE LIFE OF A

STAR(STAR CYCLE)

STAGES IN THE LIFE OF A

STAR(STAR CYCLE)

Protostar StageGravity pulls the Hydrogen gases together thus increasing its density, internal pressure and temperature which initiates fusion reaction.

Main Sequence StageStar grows more massive and with increased surface temperature. It uses up its Hydrogen fuel as it shines brighter

Red Giant StageFewer Hydrogen fusion reactions, less energy is released and the star starts to collapse. Its outer layers begin to expand, increasing

its surface area. Amount of radiation decreases and it acquires the properties of a brilliant red giant. What follows depend on how massive the star is…

The core of the Red giant is gradually converted into Carbon. The star expands and contract and the outer layer gets blown-off forming planetary nebulae.

The remaining Carbon core contracts to form a small, dense white dwarf star until it finally cools into a lump of Carbon in space.

*The Final Stage of a Less Massive Star

The core of the Red giant is gradually converted into Carbon. The star expands and contract and the outer layer gets blown-off. The remaining Carbon core undergoes fusion reaction

producing new elements until the stable atom of Iron is reached. The core collapses from intense heat and pressure due to its massive gravity. It explodes catastrophically forming a supernova.

**The Final Stages of a Massive Star(Supernova Stage)

END OF A SUPERNOVA

Neutron Star StageThe supernova produces a brilliant light that may last for months before it begins to dim. Iron core collapses even further and evolves

into heavier elements thus, forming what is called a neutron star.

Pulsar StageA neutron star starts to emit a uniform series of electromagnetic impulses which emit visible light that sweeps through space at

regular intervals.

Black Hole StageThe force of gravity in the core reaches its limits causing it to finally collapse. It becomes very, very dense that even light

cannot escape through it.

SUMMARY OF A STAR’S LIFE

CYCLE

SUMMARY OF A STAR’S LIFE

CYCLE