Download Neutron Star - Perry Local Schools

Key Ideas
〉How are stars formed?
〉How can we learn about stars if they are so far away?
〉What natural cycles do stars go through?
What Are Stars?
• How are stars formed?
• Stars are formed from clouds of dust and gas,
or nebulas, and go through different stages as
they age.
• star: a large celestial body that is composed of
gas and emits light
• light-year: the distance that light travels in one
year; about 9.46 trillion kilometers
Stars
• Stars are powered by nuclear fusion reactions.
– The core of a star is extremely hot, extremely dense,
and under extreme pressure.
– Nuclear fusion takes place in the core of a star.
– Fusion combines the nuclei of hydrogen atoms into
helium.
– When two particles fuse, energy is released.
Visual Concept: Nuclear Fusion
Stars
• Nuclear fusion takes place in the core of a star.
• Fusion combines the nuclei of hydrogen atoms into
helium.
• When two particles fuse, energy is released.
-Two hydrogen atoms come together to form 1 helium
atom.
This energy
given off by
the nuclear
power, makes
the sun, and all
stars, shine
brightly.
Stars
• Energy moves slowly through the layers of a star.
– Energy moves through the layers of a star by
convection and radiation.
– During convection, hot gas moves upward, away
from the star’s center, and cooler gas sinks toward the
center.
– During radiation, atoms absorb energy and transfer it to
other atoms in random directions. Atoms near the star’s
surface radiate energy into space.
Structure of the Sun
Studying Stars
• How can we learn about stars if they are so far away?
• The telescope allowed astronomers to study stars in
more detail for the first time.
• Some stars appear brighter than others.
– The brightness of a star depends on the star’s
temperature, size, and distance from Earth.
– The brightest star in the night sky, Sirius, appears so
bright because it is relatively close to Earth.
Studying Stars
• We learn about stars by studying energy.
– Stars produce a full range of electromagnetic
radiation, from high-energy X-rays to low-energy
radio waves.
– Scientists use optical telescopes to study visible light
and radio telescopes to study radio waves emitted
from astronomical objects.
– Earth’s atmosphere blocks some wavelengths, so
telescopes in space can study a wider range of the
spectrum.
Studying Stars
• Spectral lines reveal the composition of stars.
– The spectra of most stars have dark lines caused by
gases in the outer layers that absorb light at that
wavelength.
– Each element produces a unique pattern of spectral
lines.
– Astronomers can match the dark lines in starlight to
the known lines of elements found on Earth.
Studying Stars
• A star’s color is related to its temperature.
– Hotter objects glow with light that has shorter
wavelengths (closer to the blue end of the spectrum).
– Cooler objects glow with light that has longer
wavelengths (closer to the red end of the spectrum).
– Hot stars emit more energy at every wavelength than
cooler stars do.
Visual Concept: Types of Stars
Studying Stars
• If you look up in the sky at
night, you see stars!!!
• Astronomers, scientists who
study the universe, classify
stars according to their
physical characteristics.
• These include:
1. Color
2. Temperature
3. Size
4. Brightness
Color and Temperature
• Stars are very bright and very hot, but…
• Like on Earth, the different colors of flames/light,
reveals different temperatures.
• Stars range from colors that are red (the coolest) to
Yellow (our Sun) to white and blue colors, which are the
hottest stars.
Size
• Stars come in different sizes.
1. White dwarf- about size of earth, usually a star
that is dying off (running out of fuel)
2. Medium size- our Sun is a medium sized star.
3. Large stars- they are usually the hottest (blue)
stars.
4. Super giants- so big that it would fill our solar
system from the sun to Jupiter, but they are
usually a much cooler star (red color)
Brightness depends on BOTH size and temperature.
H-R Diagram
The Life Cycle of Stars
• What natural cycles do stars go through?
• In a way that is similar to other natural cycles,
stars are born, go through various stages of
development, and eventually die.
• The sun formed from a cloud of gas and dust.
– The sun formed about 5 billion years ago.
– Stars do not last forever.
– The sun was “born” when the process of fusion began
in the core.
The Life Cycle of Stars
• The sun has a balance of inward and outward forces.
– The fusion reactions in the core of the sun produce an
outward force that balances the inward force due to
gravity.
– Over time, the percentage of the sun’s core that is
helium becomes larger.
– Scientists estimate that the sun can continue nuclear
fusion for another 5 billion years.
Life Cycle of Stars
The first stage of a star’s life is called: Protostar
1.
2.
3.
Stars begin as a Nebula: a large cloud of gas and dust in
space.
Gravity pulls the gas and dust together to form what we call
a protostar.
The sun was “born” when the process of fusion began in the
core.
Protostar
Nebula
High Mass
Star
Star
4. When a star is “born” it lives (like our sun is right now) for
about 10 billion years. Then is starts to run out of fuel.
5. Eventually they will become super giants (which means that
the sun will get so big that it will engulf the first 4 planets,
including earth)!!!
6. Then it either explodes and forms a supernova, or a white
dwarf.
High Mass
Star
Star
7. (A) If a supernova forms then the star will eventually form either a
black hole or a neutron star.
Black Hole- where the gravity is so strong that everything, even light, gets
sucked into the hole. No one really knows where it goes!!!
Neutron Star- Similar to a white dwarf but much smaller and more dense.
8. (B) If a white dwarf forms that means that whatever is left after the fuel
is gone collapses to form a small glowing sphere in outer space!
The Life Cycle of Stars
• Some supernovas form neutron stars and black
holes.
– If the core that remains after a supernova has a mass
of 1.4 to 3 solar masses, the remnant can become a
neutron star.
– If the leftover core has a mass that is greater than
three solar masses, it will collapse to form a black
hole.
• black hole: an object so massive and dense that
not even light can escape its gravity
The Life Cycle of Stars
• The sun will become a red giant before it dies.
– As fusion slows, the outer layers of the sun will
expand.
– The sun will become a red giant.
• red giant: a large, reddish star late in its life cycle
– When the sun runs out of helium, the outer layers will
expand and eventually leave the sun’s orbit.
– The sun will become a white dwarf.
• white dwarf: a small, hot dim star that is the
leftover center of an old star
The Life Cycle of Stars
• Supergiant stars explode in supernovas.
– Massive stars evolve faster, develop hotter cores, and
create heavier elements through fusion.
– The formation of an iron core signals the beginning of
a supergiant’s death.
– Eventually the core collapses and then explodes in a
supernova.
• supernova: a gigantic explosion in which a
massive star collapses and throws its outer layers
into space, plural supernovae
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