Unit 4 Honors Astronomy

What are the three main parts of the Milky Way’s structure?

Disk, bulge, halo

Disk

Most of interstellar matter

Bulge

Most of stars

Halo

Most of dark matter

What holds all the components of the Milky Way together?

Gravity

Pop 1

Young, blue, disk, circular in disk, high heavy element content

Pop II

Old, red, bulge & halo, plunging through disk, low heavy element content

What are the two types of star clusters?

Open and globular

Open cluster

Smaller, found in disk. “The Pleiades”

Globular Cluster

Larger, found in bulge/halo, “Omega Centauri”

What two components make up interstellar matter?

Gas and Dust

Gas is made of…

H & He

Dust is made of…

Ice and iron compounds

What is located at the center of the Milky Way galaxy? How do we know?

Super massive black hole; star orbital speed, see nothing at the center

The three steps to the collapse model of the formation of the Milky Way

1. Large cloud of interstellar matter collapses

2. Supernova’s add heavy elements

3. Stars continue to form in disk, leaving older (pop II ) stars in center

What does the collapse model fail to account for?

Collisions with other galaxies

What is going to happen to the Milky Way in 4 to 5 billion years? What kind of things will happen as a result of this?

Collide with Andromeda; interstellar matter becomes locked up in stars

What is a galaxy? what shapes them?

Collection of stars and interstellar matter held together by gravity, gravity shapes them

What are the three main types of galaxies?

Elliptical, spiral, irregular

What are the two subtypes of galaxies?

S0, barred spiral

What is a spiral galaxy? What color are the arms in the center? What Does the color indicate? Where is most of the interstellar matter?

Has two or more arms or originating from the center; Blue arms because of young, massive stars, forming from high concentration of interstellar matter

What is an elliptical galaxy? What shape do they have? What color do they most often appear? How much interstellar matter do they contain?

Galaxy with an; Lack arms; Usually read from older stars and not a lot of interstellar matter

What is in a regular galaxy? What shape do they have? Why? How much interstellar matter do they contain?

Galaxy with no shape or structure because of gravity from other galaxies distorting them; Contain a lot of interstellar matter usually

What is a barred spiral galaxy?

have two arms originating from an elongated central region

what is an S0 galaxy?

Have disk systems with the arms of interstellar matter (a spiral without a spiral)

What type of galaxy is the Milky Way?

Spiral

What do we use the Hubble Tuning Fork for?

To classify galaxies

What is Hubble’s law? What do we use it for? Briefly explain the process…

V = H * D; to determine the distance to a galaxy

What happens when galaxies collide? What happens when galaxies pass by each other?

Change in shape, Type of galaxy, amount of interstellar matter, Star formation

What is the Hubble deep field? How did we gather this information? How many galaxies do we estimate are in the universe today?

Image of the farther galaxies we can see; taken from many pictures over hundreds of hours, looking at the same area in the sky; 2 trillion galaxies

How might a galaxy change type over time?

Collision with another galaxy

What is an active galaxy?

Galaxy that emits a lot of radiation/energy from their core

What are the three types of active galaxies? What do all of them have in common?

seyfert galaxy, radio galaxy, quasar

What is a seyfert galaxy?

Spiral galaxy with an extremely luminous core

What is a Quasar? Where did the name come from?

Most distant and most radiant objects in the universe; Black holes that take in too much matter at once so it is shot out into space in huge jets of energy

How far away are most Quasars?

Billions of light years

how might a supermassive black hole be created?

A massive star goes supernova and turns into a black hole that keeps taking in material and growing in size

True or false: The eventual size a galaxy can reach depends on the black hole at center

True

Explain how we never see “real time” in space…

It takes time for light to travel

Do quasars last forever? What determines how long they will last?

No; When they run out of interstellar matter

Galaxies are found in groups called…

Clusters

What is the local group? What are the three biggest galaxies in this group? How many total galaxies are in this group?

The cluster of Galaxy’s we belong in (Andromeda); three largest are spiral galaxies, 30 total

What is a super cluster?

“ a cluster of clusters”

What supercluster are we a part of?

The Virgo supercluster

Super clusters combined to form bigger structures called…

Filaments

What is the order to get to filaments?

Stars➡galaxies➡clusters➡Super clusters ➡Filaments

what accounts for the difference between calculated mass and observed mass in galaxies?

Dark matter

What is dark matter?

The glue of the universe

What types of objects can’t be ruled out for dark matter?

MACHOs (old white dwarfs, Neutron stars, Black holes), neutrinos, WIMPS

What evidence do we have that dark matter exists?

• galaxy rotation curves ( Star is moving fast faster than they should on outside of the galaxy)

• Gravitational lensing ( Light from distant galaxies is bent when it passes through a large collection of dark matter)