Download Galaxies

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Week of: 1/26-1/30
In your Table of Contents
• Today’s date is January 26, 2015.
• Add Galaxies Notes to your Table of
Contents. This will take up two
pages.
• Add Stars Notes to your Table of
Contents. This will take up two
pages.
Galaxies
• Pages: 234-237
• Galaxies are large
groupings of stars in
space.
• Galaxies come in a variety
of sizes and shapes.
• The largest galaxies
contain more than a
trillion stars.
• Galaxies began to be
classified by their shapes
in the 1920s by Edwin
Hubble.
Types of Galaxies
• Spiral Galaxies- a huge bulge at the center
and very distinctive spiral arms.
• Hot blue stars in the spiral arms make the
arms in spiral galaxies appear blue.
• The center of the galaxy appears yellow
because it contains cooler stars.
Types of Galaxies
• Elliptical galaxies have
very bright centers and
very little dust and gas.
• These galaxies are
cucumber shaped with
the round end facing us.
• Because there is so little
gas, there are no new
stars forming, and
therefore elliptical
galaxies contain only old
stars.
Types of Galaxies
• When Hubble first classified
galaxies, he had a group of
leftovers. He named them
“irregulars.”
• Irregular galaxies are
galaxies that do not fit into
any other class.
• As their name suggests, their
shape is irregular.
• The gravity of large spiral
galaxies may be distorting
the shape of these galaxies.
Contents of Galaxies
• Galaxies are composed of billions and
billions of stars. But besides the stars and
the planetary systems many of them
probably have, there are larger features
within galaxies that are made up of stars or
the material of stars.
Nebulas
• In space, nebulas are giant
clouds of gas and dust.
• Some types of nebulas
glow by themselves, while
others absorb light and
hide stars.
• Some nebulas are regions
where new stars form (like
the Eagle nebula to the
left).
• Spiral galaxies generally
contain nebulas, but
elliptical galaxies do not.
Quasars
• Among the most distant
objects are quasars, which
look like tiny points of
light.
• Quasars are among the
most powerful energy
sources in the universe.
• The quasar at the right is
as powerful as 10 billion
suns.
• Some scientists think they
may be young galaxies with
massive black holes at
their centers.
Learn about the Galaxy Video
Pictures of the Hubble Telescope
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The Truth about Stars
Stars
• Pages: 228-233
• Most stars look like faint dots of light in the night
sky.
• But stars are actually, huge, hot, brilliant balls of
gas trillions of kilometers away from Earth.
• How do astronomers learn about stars when they
are too far away to visit? They study starlight!
Which has the hottest flame?
Number 4, the blue flame, is actually the hottest!
Color of Stars
• The different colors of different
stars mean that they have different
temperatures.
• Red is a “cooler” color
• Blue is a “hot” color
Classifying Stars
• Stars are classified by how hot they are.
• Class O stars are blue- they are very hot,
the hottest of all stars.
Types of Stars
Clas
s
Color
Surface
Temperature (°C)
Elements detected
Examples of stars
O
blue
above 30,000
helium
10 Lacertae
B
blue-white
10,000-30,000
helium and hydrogen
Rigel, Spica
A
blue-white
7,500-10,000
hydrogen
Vega, Sirius
F
yellowwhite
6,000-7,5000
hydrogen and heavier
elements
Canopus, Procyon
G
yellow
5,000-6,000
calcium and other metals
The sun, Capella
K
orange
3,500-5,000
calcium and molecules
Arcturus, Aldebaran
M
red
less than 3,500
molecules
Betelgeuse, Antares
Distance to the Stars
• Because they are so far away,
astronomers use light-years to give the
distances to the stars.
• A light-year is the distance that light
travels in one year.
• Because the speed of light is about
300,000 km/s, it travels almost 9.5
trillion kilometers in one year.
The Life Cycle of Stars
The star formation
region N11B in the LMC
(our neighborhood
galaxy) taken by
WFPC2 on the
NASA/ESA Hubble
Space Telescope.
• Just like people, stars are born, grow old,
and eventually die.
• They are born when clouds of gas and dust
come together and become very hot and
dense.
The Life Cycle of Stars
• As stars get older, they
lose some of their material.
• Usually this is a gradual
change, but sometimes it
happens in a big explosion.
• Either way, when a star
dies, much of its material
returns into space.
• There some of it combines
with more gas and dust to
form new stars.
Betelgeuse is a red supergiant
star approaching the end of its
life cycle
• Stars similar to the sun are
called main sequence stars.
• What color of stars is our sun?
(HINT: use the chart on pages 230-231
to figure it out!)
When Stars Get Old
• Stars much larger than the sun may
explode with such violence that they
turn into a variety of strange new
objects.
Supernova
• A supernova is basically
the death of a large star
by explosion.
• A supernova explosion is
so powerful that it can
be brighter than an
entire galaxy for several
days.
• Heavy elements, such as
silver, gold, and lead, are
formed by supernova
explosions.
Black Holes
• Sometimes the leftovers
of a supernova are so
massive that they
collapse to form a black
hole.
• A black hole’s gravity is
so strong that it can pull
in material from a nearby
star and not even light
can escape.
Supernova & Death of a Star
Meet the Black Hole Experts