science Flashcards
nuclear fusion occurs in an environment of
extreme density and heat
heat and density cause the atoms to
lose their electrons and collide with great force
with nuclei that fuse during nuclear fusion
more energy is released which heats nearby nuclei
the proton-proton chain is
the dominant form of nuclear fusion
the proton-proton chain begins when
an ordinary hydrogen is stripped of its electron and becomes a single proton
four hydrogen protons are then
fused together to form a single helium nucleus
The end result of the proton-proton chain is
a helium nucleus composed of two protons and two neutrons, as well as a colossal amount of energy
lighter elements can be used to build
heavier elements
in the periodic table, lighter elements appear near the top while
heavier elements are farther down
Some stars that are hot enough have the ability to fuse helium nuclei to create
nitrogen, oxygen, carbon, and other elements
Nuclear fusion cannot produce elements heavier
than iron (symbol Fe
the formation of elements stronger than iron can only occur at
the very end of a star’s life
humans consume about
3.89 × 1020 joules of energy every year.
How long a star will live has a lot to do with its
mass
Stars with greater mass consume their fuel
much faster
A large star can put out
huge amounts of energy, and consumes its fuel incredibly quickly.
A smaller star consumes its fuel
very slowly
Stars with a greater overall mass are
brighter and hotter, and they consume their nuclear fuel faster.
Luminosity is the term for a star’s actual
brightness.
The HR diagram is a tool astronomers use to study how stars
evolve
Star’s color is determined by its
temperature
a star’s luminosity is determined by its
size.
Small and medium-sized stars begin their lives by gradually converting
hydrogen into helium.
Because small and medium-sized stars are cooler, they consume fuel very
slowly.
After all fuel resources have been used up, the star will emit enormous pulses of
energy
These pulses will push the outer layers of the star away, creating a cloud of
ionized gas.
At the center of this cloud is the
core of the star, (a white dwarf)
As the white dwarf cools, its light becomes
dimmer and redder.
Large stars go through the supernova stage where they collapse and turn into either a
neutron star or a black hole.
When a large star begins to exhaust its fuel supply, it starts fusing
hydrogen from outside its core
The result of the fusing is a
red supergiant.
A stellar nebula is a cloud of
interstellar gas and dust
a stellar nebula is also the
birthplace of a star
the collapse of a medium-sized star leads to a
planetary nebula
Before the formation of our solar system, there was a supernova event that sent out an enormous cloud of
gas and dust.
The cloud stabilized to form a slowly spinning
nebula.
The nebula that formed before our solar system was primarily composed of
hydrogen, helium, carbon, oxygen, nitrogen, and silicon.
the supernova event had produced heavy elements too, such as
gold, copper, uranium, and lead.
Although the nebula was spinning very slowly, the rotation was enough to cause it to
flatten out
Eventually, the disk-shaped nebula began to
shrink
This event marked the birth of the,
Sun
As gravity pulled the disk-shaped nebula inward
it spun faster and faster
The nuclear reactions occurring within the Sun grew stronger, and it began emitting tremendous amounts of
electromagnetic radiation.
These nuclear reactions created a lot of
heat
Because gases cannot condense at such high temperatures, the region close to the Sun became unsuitable for the formation of
gaseous planets.
outward pressure caused by the Sun’s radiation pushed many of the lighter elements to the farther reaches of the solar system. Once these gases were pushed out far enough, they could cool, condense, and begin to form the
gas giant and ice giant planets.
