Download What are stars? - Manhasset Schools

TOPIC: Astronomy
AIM: What are
stars?
•Ball
of
gases
that
Star
gives off light
and heat
•
Universe
began
with
a
The Big
giant explosion 13
Bang
billion years ago
Theory
• Matter  stars
• It is still expanding
• Most accepted theory
What •Nearest star to
is the Earth
Sun?
What • Hydrogen and
helium
gases
are
stars
made
of?
How • 1. Nebula (large cloud
of gas, ice, and dust)
do
forms
stars
form?
The Orion Nebula, a site of active star
formation. From the Hubble Space
Telescope.
The above images show the Eagle Nebula
star-forming region in the Infrared (left)
compared with a visible light image by
Hubble Space Telescope (right).
• 2. Nebula contracts (due to
gravity) & breaks up into
smaller pieces
• 3. Temperature increases
(1 million K)
• 4. Center = protostar forms
• 5. Temp reaches 10 million K
• 6. H fuses to make He 
star
H-R
•HertzsprungDiagram Russell Diagram
•Higher temp
stars radiate
more energy
• 90% of all stars fall on main
sequence (line from upper left
to lower right)
Our sun has been a main sequence
star for 5 billion years and will stay a
main sequence star for another 5
billion years.
How do • 1. Shrinks
stars • 2. Increases in
change? density
• 3. Temp increases
• 4. Moves into main
sequence (when
fusion starts)
Types • 1. Giant = late stage
• (When H is used up)
Of
• Core contracts, temp
stars increases
• Outer layers expand &
cool
• a. Red Giant = large bright
star, fairly cool
• b. Super Giant = very large
stars
• Example: Betelgeuse
Betelgeuse is located in the constellation of
Orion. It’s diameter is larger than the
diameter of Jupiter’s orbit around the Sun.
• Can eventually collapse, outer
portion explodes  SUPERNOVA
(giant explosion)
• Supernova can turn into a
neutron star OR a black hole
A supernova is a giant explosion in which the temperature in
the collapsing core reaches 10 billion K and atomic nuclei are
split into neutrons and protons. Protons merge with electrons
to form neutrons, and the collapsing core becomes a neutron
star. A typical neutron star is the size of a major city on
Earth, but has a mass greater than the Sun’s.
Hubble Space Telescope image of a neutron star (identified
by the arrow) in the direction of the southern constellation
Corona Australis. The star has a surface temperature of
1.2 million degrees Fahrenheit, which is far hotter than
that of ordinary stars.
• Black hole = object so dense that
nothing can escape its gravity
• Usually results from the supernova
of a very massive star
• 2. White dwarf = giant that lost
outer layers
• Very small, hot star, Hot dense core
• Keeps contracting due to gravity
A giant’s core will continue to contract and become hotter.
When it uses up all its helium, it contracts even more. When
the temperature reaches 100 million K, helium fuses, forming
carbon. Now the star is enormous and its surface is much
cooler. Its outer layers escape into space leaving behind a hot,
dense core that continues to contract and is now called a white
dwarf which is about the size of Earth.
There are many white dwarfs in our
galaxy, but most are too dim to be seen.
One of the first to be discovered was
Sirius B, the dense companion star to
Sirius.
Life Cycle of a Star
Nebula
Black
dwarf
Protostar
Giant
White
dwarf
Super Giant
(SUPERNOVA)
Neutron
Star
Black
Hole
What is a
• Star pattern that
constellation? appears to form
images
• Used by
astronomers to
locate and name
stars
•
Instrument
used
to
Telescope
observe objects in
outer space using
lenses