Download Milky Way Galaxy

Standard 2.d– Know the types of equipment
astronomers use to study space
Big Deal:
How can astronomers see
objects in space that are
so far away?
Objects in space give off different types of
electromagnetic radiation which allow us to
understand things about them.
Electromagnetic radiation – a wave in space that
has both electric and magnetic properties
Visible light – given off by lights in our home
X-rays – used for medical purposes and for security reasons
Radio waves – used to broadcast music, television signals
Radio Telescopes
Very Large Array, New Mexico
Location
Key
Features
Limitations
Advantages
Study
Subjects
Arecibo Observatory, Puerto Rico
Radio Telescopes
Arecibo Image of Venus
VLA Image of M87 Galaxy
Location
Isolated regions (valley floors) to avoid other radio signals
Key
Features
Large radius because of weak signals; array of many to
pinpoint locations
Limitations
Interference with other radio signals; poor resolution
Advantages
Images can be detected through interstellar dust; Images
can be detected from objects that are too cool to give off
light
Study
Subjects
Distant galaxies, supernova remnants
Optical Telescopes
Palomar Observatory, California
Hubble Space Telescope
Location
Key
Features
Limitations
Advantages
Study
Subjects
Optical Telescopes
Palomar Image of Moon Crater
Hubble Image of Messier 101
Location
Typically up high (mountains, space) to avoid light pollution
Key
Features
Large domes to shield out light
Limitations
Scattering of light by atmosphere
Advantages
Images can be directly viewed; most common and user
friendly telescope
Study
Subjects
Planets, stars, near galaxies
X-ray Telescopes
Chandra Space Observatory
Location
Key
Features
Limitations
Advantages
Study
Subjects
XMM Newton X-Ray Telescope
X-ray Telescopes
XMM Image of RSW86 Supernova
Chandra Image of Cas A Supernova
Location
Up in space orbiting around Earth
Key
Features
Orbiting because x-rays do not penetrate the atmosphere
Limitations
Hard to maintain
Advantages
Images can be detected from objects that do not give off
visible light (like black holes)
Study
Subjects
Black holes, supernovas
Standard 2.d– Know the types of equipment
astronomers use to study space
Bottom Line:
Astronomers use optical
telescopes, radio telescopes,
and X-ray telescopes to study
different parts of the universe
Standard 2.g– Know the evidence for how the
universe has been expanding
Big Deal:
How did the present
universe come about?
Cosmology – the study
of the origin, nature,
and evolution of the
universe
To explain the origin of
the universe, most
scientists believe in the
Big Bang Theory.
Big Bang Theory -- the theory stating that universe began as
a point in space about 13.7 billion years ago and has been
expanding ever since.
Lots of different scientists
contributed, but much of
the work was done by
Edwin Hubble in the 1920’s
and 1930’s
The biggest evidence for
the Big Bang was the
redshift of galaxies.
What is redshift?
When a wave source
moves, waves change
shape.
Wave sources that move
away cause waves to
stretch. Wave sources
that move closer cause
waves to compress.
Sound changes pitch.
Light changes color.
Galaxies are made up of stars
that give off light (EM
radiation). The types of
radiation depends on the
source.
Hubble expected to find certain
wavelengths of radiation from
certain galaxies.
What he actually noticed was
that waves were actually longer
than expected.
Having longer waves caused
them to appear red – a
“redshift”
If the majority of galaxies are “redshifted”, they are moving
away from the center and the universe is expanding as a
whole.
Because of Hubble’s original work, we now know:
•That everything in
the universe
started from a
single point in
space.
•That is all began
about 13.7 billion
years ago.
•That the universe
is continuing to
expand
Standard 2.g– Know the evidence for how the
universe has been expanding
Bottom Line:
An explosion 13.7 bya caused
all of the matter in the
universe to expand from a
singular point in space.
Standard 2.b– Know what a galaxy is and what it
contains
Big Deal:
Where is most of the mass
of the universe found?
The universe is composed of galaxies that come in
different shapes and characteristics.
Sombrero Galaxy – 29 million ly
M81 Galaxy –away
12 million ly away
Galaxy – a group of stars, dust, and gas held
together by gravity
Sprial Galaxy
Cause
Contraction by
gravity
Abundance
Less common
but easily
seen
Brightness
Very bright
Other
Lots of
Components interstellar
gas
Star
Formation
Forms new
stars
Size
Very Large
Movement
Rotating arms
Shape
Disk-shaped
Elliptical Galaxy
Cause
Colliding
galaxies
Abundance
Most common
Brightness
Dim
Other
Little gas and
Components dust
Star
Formation
Doesn’t make
new stars
Size
All sizes
Movement
No rotation
Shape
Elongated or
spherical
Irregular Galaxy
Cause
Interacting
galaxies
Abundance
Rare
Brightness
Somewhat
Bright
Other
Components
Lots of
interstellar gas
Star
Formation
Forms new
stars
Size
Small
Movement
No rotation
Shape
No specific
shape
Galaxies are parts of galaxy clusters, which are groups
of galaxies held together by gravity.
Milky Way Galaxy
100,000 ly across
Andromeda Galaxy
2.5 million ly away
(closest spiral galaxy)
The Milky Way Galaxy and the Andromeda Galaxy
belong to the Local Galaxy Cluster (LGC)
Standard 2.b– Know what a galaxy is and what it
contains
Bottom Line:
Most of the mass of the
universe is found in one of
three types of galaxies –
spiral, elliptical, or irregular
galaxies.
Standard 2.b– Know how big a galaxy is
Big Deal:
How do astronomers
measure distances in
space?
Distances on the Earth are measured in miles
Circumference of Earth -- 25,000 miles.
Distance to moon -- 240,000 miles
Distances in our solar system are most conveniently
measured in astronomical units (AU).
1 AU = the distance from the Earth to the Sun
(93 million miles)
Distance to Mars -- 1.5 AU (140 million miles)
Distance to Neptune -- 30 AU (2.8 billion miles)
Distances beyond our solar system are most conveniently
measured in light years (LY)
Light travels 186,000 miles per second.
1 light year = the distance light travels in one year
(6 trillion miles)
Proxima Centauri is the closest
star outside of our solar system.
It is 270,000 AU away or 4.2 light
years away.
Canis Major is the closest galaxy
outside of the Milky Way
It is 1.6 billion AU away or
25,000 light years away.
Standard 2.b– Know how big a galaxy is
Bottom Line:
Astronomical units are used
to measure things in our
solar system and light years
are used to measure things
beyond that
Standard 2.b– Know what a galaxy is and what it
contains
Big Deal:
What happens inside of a
spiral galaxy like the Milky
Way?
The galaxy we belong to is
called the Milky Way Galaxy.
A few facts about the Milky
Way:
100,000 light years
•Our sun is one of over 100
billion stars in the Milky Way
galaxy
•The Milky Way is just one of
billions of galaxies in our
universe
•The Milky Way is about
100,000 light-years across
and 10,000 light-years thick
10,000 light years
•It is a spiral
galaxy with arms
that rotate around
the center because
of gravity
•It is believed that
there is a black
hole at the middle
Black Hole
Basic Parts of the Milky Way
(and other spiral galaxies)
Arms – the rotating
projections coming out of
the center. This is where
stars are born
Nucleus – the center of the
galaxy where stars
eventually die
Disk – the collection of
arms that project in a plane
from the center
Basic Parts of the Milky Way
(and other spiral galaxies)
Halo – the region in space
above and below the disk
containing small clusters of
stars
Globular Clusters – groups
of stars around the galactic
disk that move
independently
Standard 2.b– Know what a galaxy is and what it
contains
Bottom Line:
Spiral galaxies rotate
because of gravity and are
where stars are born.
Standard 2.b– Know the different types of stars
Big Deal:
How do other stars
compare to the Sun?
All stars exist because of a balance in the star
between gravity and nuclear fusion (like in our Sun).
Stars are different
due to their:
•Temperature
•Brightness
•Size
•Elements that
form
Star Temperature
Blue stars
are very hot
White stars
are hot
Yellow stars
are warm
Red stars
are cool
Star Brightness
Apparent Magnitude – measures how
bright a star appears to be based on how
big it is, how hot it is, and how far away it
is (the larger the number, the dimmer the
star)
Absolute magnitude –
measures a star’s actual
brightness regardless of its
distance away (as if they were
side-by-side
A H-R diagram
categorizes
stars based on
their
temperatures,
their sizes, and
their brightness
Star Size
Low-mass stars:
•Are red in their
main sequence
stage and produce
helium from
hydrogen
•Have NO giant
phase
•Change to white
dwarfs when fusion
stops
Star Size
Medium-mass stars
(like our Sun):
•Are yellow in their main
sequence stage and
produce helium from
hydrogen
•Change to red giants and
produce carbon/oxygen
•Change to white dwarfs
when fusion stops
Star Size
Massive stars:
•Are blue in their main
sequence stage and produce
helium from hydrogen
•Change to supergiants and
produce heavier metals like
iron and nickel
•Collapse dramatically when
fusion stops forcing an
explosion called a supernova
(which creates even heavier
metals like gold)
•Form either a neutron star or
a black hole if large enough
Star Size
Standard 2.b– Know what a galaxy is and what it
contains
Bottom Line:
Spiral galaxies rotate
because of gravity and are
where stars are born.