Galaxies

Galaxies

Objective:
I can identify galaxies based on shape and formation.

1.

​On your table collaborate with your peers and draw what you think a galaxy would look like.

Future Quiz/ NTK

●Big Bang Explosion - 13.8 BYA

○First 3 Elements Created in BB (Hydrogen, Helium, Lithium)

○Hubble - Studied BB

●Red Shift = Objects Moving Away

●Cosmology = Study of Universe

●Types of Galaxies (Spiral, Barred, Elliptical, Irregular)

○Elliptical = few young stars, elongated

■most circular = E0

■most elongated = E7

○Identify Galaxies from Pictures (All 4)

○Galaxies Grow through Cannibalism

Galaxy

Matching

1.

Spiral = Denoted by letter S and classified by type a, b, c (according to size of central bulge)

2.

Barred Spiral = SB
Different from ordinary spirals mainly because of the presence of an elongated “bar” in the middle

3.

Elliptical = E0 (circle) →
E7 (elongated circle)

4.

Irregular = Irr

Galaxies

●Galaxies are a large collection of gas, dust, and stars bound together by gravity

●Galaxies have billions to trillions of
stars contained in them. Most galaxies have more stars in them than the number of people who have ever lived on Earth!

●Our current estimate on the number of
galaxies in the universe is about 200
billion to 2 trillion.
Consisting of 3 beautiful galaxies M66 and M65 (from the Messier Catalogue) and NGC 3628, each member of the Leo Triplet is a spiral galaxy, although it may not initially appear as though this is the case.

The Leo Triplet

Multiple Choice

• Galaxies are a large collection

• • Located at the core of most galaxies

  • Formed by the repeated collision of stellar mass black holes (5 – 10 M☉) 

• • gas, dust, and stars bound together by gravity

• • Have no arms or flattened galactic disk

  • Exhibit little internal structure of any kind

  • Contain little to no gas and dust

• Nitrogen, Oxygen and Helium

Galaxy Formation

Just after the Big Bang, gas
(mostly hydrogen and helium)
and dust started to collapse into
protogalactic clouds

●Grouping of gas caused areas of
low/high density

Protogalaxy

Galaxy Formation

●Protogalactic clouds started to
form stars (because gravity!)

●As they collapsed, the clouds
began to rotate

●As the clouds rotated, they got
stronger and started to pick up
more gas and dust

M81 - Bode’s Galaxy

Galaxy Growth

●Galaxies grow through cannibalism,
aka collision with other galaxies

●Because of the vast amount of
empty space, it’s more like a
meshing than a collision

●The collision distorts the shape.

●Old stars collect in the center. New
stars form on the edge. NASA's Hubble Space Telescope, has captured a spectacular pair of galaxies engaged in a celestial dance of cat and mouse or, in this case, mouse and mouse. Located 300 million light-years away in the constellation Coma Berenices, the colliding galaxies have been nicknamed "The Mice" because of the long tails of stars and gas emanating from each galaxy. Otherwise known as NGC 4676, the pair will eventually merge into a single giant galaxy.

The Mice Galaxies
NGC 4676

Multiple Choice

Can Galaxies can be considered cannibalistic?

• True

• False

Consequences of Collisions

●More gas and dust collect, allowing for the
formation of new stars.

●Collisions of gas clouds accelerate star
formation.

●Larger stars are born, leading to bright, blue
stars (Type O, type B)

●Supermassive Black Holes grow larger
The graceful, winding arms of the majestic spiral galaxy M51 (NGC 5194) appear like a grand spiral staircase (sweeping through space. They are actually long lanes of stars and gas laced with dust.

The Whirlpool Galaxy

Supermassive Black Holes

●Located at the core of most galaxies

●Formed by the repeated collision of stellar
mass black holes (5 – 10 M☉)
○M☉ = Mass of the Sun

●Supermassive Black Holes have a mass of
100,000 - 1,000,000,000 M☉

●Ultramassive Black Holes are theoretical, and
have a mass of 10 billion + M☉

Supermassive Black Hole in M87

Multiple Choice

Where are the most supermassive black holes

• In most constellations
• It is unkown
• In the center or core of most galaxies

• Right next to large stars

Organization of Galaxies

●Galaxies tend to collect together to create groups
of galaxies. They are called Galaxy Clusters.

●The Local Group is our local neighborhood of
galaxies.

●The Local Group consists of 50 galaxies.

●Milky Way and Andromeda are the two largest in
the Local Group.

●In about 4.5 billion years, the Milky Way and
Andromeda will collide, to form “Milkomeda”

​The Virgo Cluster is part of the Virgo Supercluster
A supercluster contains about 100 galaxy clusters within it. 

Your Galactic Address

●What is your galactic address?

●See if you and your table can get the right address! Research and collaborate with your table to come up with your cosmic address!

Hubble’s Galaxy Classification

●Based solely in appearance

●Does not represent “aging” or
change over time.

●Has been modified since the
developed by Edwin Hubble, but
mostly still the same

.

• Spirals 

• Barred Spirals

• Ellipticals 

• Irregulars

Spiral Galaxies

●Spiral galaxies are young. Young, blue stars
are found in the edge. Old, red stars are found
in the core.

●They are rich in gas and dust, allowing for
frequent star formation.

●They have a central bulge, with one or more
arms

●Arms can be tightly wound or loose.

●Rotate around the central core.

●Identified by the letter S or SA.

NGC 2997 - Type Sc

Barred Spirals

●Different from ordinary spirals mainly because of
the presence of an elongated “bar” in the middle

●Spiral arms project from the ends of the “bar”

●They have a thick central bulge, with numerous
old, red stars

●They have have thin outer disk with one or more
arms, rich in gas and dust allowing for young, blue
stars

●Arms can be tightly wound or loose.

●Rotate around the central core.

●Identified by the letter SB

NGC 1073 - Type SBc

Elliptical

●Have no arms or flattened galactic disk

●Exhibit little internal structure of any kind

●Contain little to no gas and dust

●Contain few to none young, bright stars.

●Contain many old, red stars.

●Denoted with letter E; subdivided by
eccentricity

●E0 is close to circular, E7 is most elongated

●Has no rotation

M87 - Type E0

Irregular Galaxies

●Tend to be rich in gas and dust

●Many young, blue stars

●No regular structure

●Often look like misshapen spirals

●Smaller than spiral galaxies

●Larger than dwarf elliptical
galaxies

●Often the result of a galactic
collision.

●Classified as Irr I and Irr II

M82 - Type Irr II

Multiple Choice

What type of galaxy is this?

• Spiral
• Elliptical
• Irregular
• Irrational

Multiple Choice

What type of galaxy is this?

• Spiral
• Elliptical
• Irregular
• Irrational

Multiple Choice

What type of galaxy is this?

• Spiral
• Elliptical
• Irregular 
• Irrational

Quasars

●There are other objects in space besides stars
and galaxies.

●Quasi Stellar Radio Sources, aka Quasars are
galaxies with a supermassive black hole that is
“feeding”
○Quasars are 1000’s times brighter than
anything else in space

Quasar 3C 273