Download Stars and Galaxies

STARS AND GALAXIES
The Life Cycle of a Star: Stars
have a life cycle and evolve
over time. The mass of a star
controls its
Evolution
Lifespan
Ultimate fate (how it dies)
Our Sun: an
average
size star:
1. Stars begin as a nebula
(cloud of gas and dust) that
starts to contract due to
gravity.
2. Protostar: temperature
increases, millions of years
later the gas becomes
plasma and fusion begins.
3. Main sequence star: (the
longest stage in the life of a
star) nuclear fusion
(hydrogen fuses into helium)
continues in the core of the
star...our Sun is a main
sequence star.
Balancing Act
• Stars more massive than our Sun may be main
sequence stars for only 10 million years
• Stars less massive than our Sun may be main
sequence stars for 100’s of billions of years
• Remember: the larger the star the shorter the life
span, the smaller the star the longer the life span
A star starts to die when hydrogen runs low:
4. Giant: A star cools as it expands and starts to glow
red. Giants can be more than 10 times larger than the
sun.
5. White dwarf: outer layers escape into space, the star
collapses into a dense hot, dim star smaller than Earth.
Path of a star much larger than our sun
Path of our Sun
Massive Stars die
explosively!!
4. Supergiant: Massive stars
become larger than
giants as they leave the
main sequence….they
can be 100 to 1,000 times
larger than the sun.
5. Supernova: the explosion
of a supergiant
• Neutron Star: a small dense ball of neutrons that spin
after a supernova explosion
• Black Hole: the remnants of a supernova that are
contracted even more than a neutron star… it is so
dense light cannot escape from it.
Can you spot the supernova?
Are Black Holes
Important?
Every spiral galaxy,
like our own Milky
Way, is thought to
have a supermassive
black hole at its
center. The black
hole at the center of
the Milky Way is sort
of like the Sun at the
center of our solar
system - the galaxy
orbits the black holes
like the planets in
solar systems orbit
the stars.
ultraviolet-light exposure
Massive Stars are important because…..
During the fusion process of hotter massive stars,
elements such as iron, oxygen, silicon and magnesium
are created. These are elements needed for life.
Composition of Universe
Magnitude describes the brightness of a star
• Two types of brightness: absolute magnitude
and apparent magnitude
• Apparent magnitude is the brightness we see
here on Earth
• Absolute magnitude is the actual brightness
the star gives off. The more negative the
number, the brighter the star is!
ORION CONSTELLATION
Betelgeuse
Rigel
Rigel
To figure out
Parallax is a
how
far it is to a
method used
star,
to determine
astronomers
distance to a
star.
look at
it from
two different
positions,
called parallax
STARS ARE CLASSIFIED BY THEIR SIZE, COLOR
AND TEMPERATURE
• Not all stars are the same
color because different
elements burn different
colors. Some are red, some
are blue, etc.
• Color tells the temperature
of the star
• Hot stars are bluish/white
and cooler stars are
reddish/orange
• Astronomers call this a
star’s spectral class.
Spectral classes are O, B,
A, F, G, K, and M
Flame Test Clip
O, B, A, F, G, K, and M... (Oh Be A Fine Guy Kiss Me)
and for you guys: Oh Be A Fine Girl Kiss Me!!
Hertzsprung-Russell Diagram
(H-R Diagram)
• Stars are ranked on
the H-R Diagram
based on their
temperature and
absolute magnitude
• Most stars fall in the
middle of the
diagram, called the
main sequence
• Very few stars are
white dwarfs or
giants/supergiants
H-R Diagram---shows the life
cycle of stars
Absolute magnitude
supergiants
giants
White
dwarfs
temperature
THE 3 TYPES OF GALAXIES
• Our galaxy, the Milky Way is part of a larger
group of galaxies called the Local Group
• There are about 30 galaxies included in the
Local Group
There are three types:
elliptical, spiral, and
irregular
1. Our galaxy the Milky
Way is a spiral galaxy
The Andromeda galaxy is an
example of a spiral galaxy with huge
spiral arms. Astronomers believe the
Milky Way resembles this.
2. Elliptical galaxies are
the most common
Elliptical can be
football-shaped
3. Irregular are all the
galaxies that are NOT
spiral or elliptical, and
are not nearly as
common
Irregular
Where Are We in Our Galaxy?