Nebula with protostars

Stellar Evolution- Draw on page 64

Galaxies, Nebulae, and Stars

TEKS 8.8A describe components of the universe including stars, nebulae and galaxies, and use models such as the Herztsprung-Russell diagram for classification

TEKS 8.8B recognize that the Sun is a medium-sized star near the edge of a disc-shaped galaxy of stars and that the Sun is many thousands of times closer to the Earth than any other star

We live in a galaxy called the Milky Way. A galaxy is a system of stars, planets gas, dust and dark matter.

Within galaxies are star forming regions called nebula. A nebula is a

cloud of dust, hydrogen and helium gases.

It is in these clouds of gas and dust that

stars sometimes form.

A star is a large ball of gases that generates

its own energy through nuclear fusion.

Fusion is a process in

which hydrogen

and helium fuse to form

heavier elements.

This process generates

large quantities of

energy.

The energy is emitted from the

star in the form of heat

and light.

Stars undergo

many changes through

their evolution.

Depending on the mass of the star, its lifetime may be a few million years to trillions of

years. Lower massed stars can generate

energy for billions of years.

Stars that are very massive generate

energy for only a few million years.

Nebula with protostars

Stellar Evolution

Over the course of the star’s evolution

the energy generated by the star begins to decrease.

Ultimately, the star will

no longer have

enough hydrogen

or helium to continue to

radiate.

Our Sun is only one of many stars in the

universe.

It is considered to

be a medium-sized star near the

edge of our disc-shaped

galaxy.

So what will happen to our Sun?

At the end of the

sun’s life, it will

gradually brighten, as it has

been doing for the last

4 billion years.

Around 5,000,000,

000 AD, the

hydrogen in the

Sun’s core will run

out.

The sun will

expand into a red

giant about three times larger

than it is now.

The increased brightness will boil the oceans and raise our temperatures to over 1000 Kelvin.

Eventually, the Sun will shrink, but

then expand again,

charring the surface of the earth with solar prominences.

If earth isn’t destroyed, it will

become a cold, dark chunk of rock

circling a white dwarf.