Stellar evolution is the process by which stars change over their lifetimes, ranging from millions of years for massive stars to trillions for the least massive. Stars are born from nebulae of hydrogen and dust and evolve through stages like red giants and supernovae. Supernovae occur when massive stars explode, leaving behind neutron stars or black holes. Neutron stars are incredibly dense, while black holes have such strong gravity that nothing can escape.

1. Stellar
evolution

2. Stellar evolution is the process by which a star changes
during its lifetime.
Depending on the mass of the star, this lifetime ranges
from a few million years for the most massive to trillions
of years for the least massive, which is considerably longer
than the age of the universe.

3. Steller Nebulae, birthplaces of stars, are
clouds of hydrogen and dust in space.
Emission Nebula glows brightly because the gas in
it is energised by the stars that have already formed
within it, e.g. Orion nebula
Reflection Nebula, where starlight reflects on the
grains of dust in a nebula
Dark Nebulae are dense clouds of molecular
hydrogen which partially or completely absorb the
light from stars behind them, e.g. the Horsehead
Nebula in Orion

4. A STAR is a luminous globe of gas producing its own
heat and light by nuclear fusion.
Born from nebulae and consist mostly of hydrogen and
helium gas.
Surface temperatures range from 2000°C to above
30,000°C, and the corresponding colours from red to blue-
white.
The brightest stars have masses 100 times that of the Sun
and emit as much light as millions of Suns. They live for
less than a million years before exploding as supernovae.
The faintest stars are the Red Dwarfs, less than one-
thousandth the brightness of the Sun.

5. RED GIANT is a large bright star with a cool surface
Formed during the later stages of the evolution of a star
like the Sun, as it runs out of hydrogen fuel at its centre
Diameter's between 10 and 100 times that of the Sun
Very bright because of the size, although their surface
temperature is lower than that of the Sun, about 2000-
3000°C
Very large Red Giants are often called Super Giants, having
diameters up to 1000 times that of the Sun and have
luminosities often 1 million times greater than the Sun.

6. White Dwarf
When a star like our Sun runs out of its nuclear fuel in about
five billion years time, it will go through a beautiful death
ritual, shedding its outer layers in a blaze of color while its
inside squeezes down into a dense white hot ball about the
size of the Earth. This ball, aptly named a WHITE DWARF,
is where the story ends for the stars like Sun.

7. SUPERNOVA
The explosive death of a
star
Obtain the brightness of
100 million suns for a
short time

8. Type I Supernova
About 2/3 of all stars in a galaxy are binaries. One star may run through
its life cycle faster, becoming a white dwarf while the other star
continues to shine normally.
The white dwarf is greedy, and if the orbit of the white dwarf and its
companion is close, the white dwarf’s strong gravity begins to tug the
outer layers of hydrogen gas from the companion and wrap the gas
around itself

9. The hydrogen layer grows, getting hotter and hotter, until at a
critical temperature the bomb goes off – a thermonuclear
explosion as bright as a billion stars, and a flash that can be
seen across the observable universe
Type 1 supernova was seen in our own galaxy by Johannes Kepler in 1604, five years
before the invention of the telescope.
This image is a composite of observations from three space telescopes, Hubble (yellow),
Chandra (blue and green) and Spitzer (red) of the remnants of the star Kepler saw in the sky
four centuries ago. The ball of debris is now about 8 light years across and still expanding.

10. Type II Supernova
Occurs in stars ten times or more as massive as the Sun,
which suffer runaway internal nuclear reactions at the
ends of their lives, leading to an explosion
Leave behind Neutron Stars and Black Holes

11. NEUTRON STARS are composed mainly of
neutrons and are produced when a supernova
explodes, forcing the protons and electrons to
combine to produce a neutron star.
Neutron stars are very dense, typically having a
mass of three times the Sun but a diameter of
only 20 km.
If its mass is any greater, its gravity will be so
strong that it will shrink further to become a
Black Hole.

12. Black hole
A black hole is a region with such strong
gravitational effects that nothing—
including particles and electromagnetic
radiation such as light—can escape from it.
Black holes distort the space around them,
and can often suck neighbouring matter
into them including stars.