Galaxies Test Review

Very bright galaxies that don't fit into the categories spiral, elliptical or irregular.

Active Galaxies: Seyfert

How many galaxies have black holes at their center?

Almost all.

You see a distant car in the night. What two things must you know in order to estimate its distance?

Apparent brightness and intrinsic brightness (b&c).

A galaxy seen 1 billion light-years away means we see it...

As it was 1 billion years ago.

Where do super-massive black holes likely exist?

At the center of galaxies.

Galaxy with elongated bar of stellar and interstellar matter passing through the center and extending beyond the bulge, into the disk, spiral arms project from the ends of the bar.

Barred Spiral

A region of space having a gravitational field so intense that no matter or light can escape.

Black Hole

What happens if you poke a hole in the fabric of space & time?

Black Hole is created.

How do scientists know that black holes exist?

By observing objects and light around black holes.

Collisions between galaxies...

Cause gas and dust clouds to collide leading to rapid star formation.

Invisible substance (doesn't produce light) that makes up most of the galaxy.

Dark Matter

Which type of galaxy can grow to the greatest mass and possess the largest number of globular-clusters?

Elliptical

Which type of galaxy contains the most Population II stars?

Elliptical

Galaxy with no spiral arms, dense central nucleus with hot gas around it.

Elliptical Galaxy

The boundary around a black hole where nothing can escape its gravity.

Event Horizon

Another student tells you that the Milky Way Galaxy is made up "mostly of stars." Is this statement accurate?

False

If a space probe could be sent into a black hole, it could transmit images back to Earth.

False

Scientists only began to speculate on the existence of black holes in the twentieth century.

False

How will the Andromeda galaxy effect ours in about 2 billion years?

Galactic cannibalism, the two galaxies will collide and form one large galaxy.

What is "galactic cannibalism"?

Galaxies eat each other and get bigger.

A system of millions or billions of stars, together with gas and dust, held together by gravitational attraction.

Galaxy

Super-massive black holes likely exist in the center of every _______.

Galaxy

Which of the following is NOT one of the basic types of galaxy?

Globular

What powerful force allows black holes to absorb light?

Gravity

Why does light get bent or pulled into a black hole and can't get out?

Gravity is to big.

What happens to a star if it passes to close to a black hole?

Gravity whips it around super fast, like a slingshot.

Galaxy with rich interstellar matter and young, blue stars but lacks any regular structure.

Irregular Galaxy

Where does the matter go that doesn't get pulled into the black hole?

It forms a jet of super-heated gasses shooting out in two directions.

Stream of energy exiting both sides of a black hole.

Jets

How did Ghez and other scientists prove that there is a black hole at the center of our galaxy?

Lots of stars orbiting around an invisible point in space.

Name two basic differences between normal galaxies and active galaxies.

Luminosity and type of radiation they emit.

Based on galactic rotation curves and motions in clusters of galaxies, dark matter...

Makes up about 90% of the universe.

Our galaxy is the ___________, which is a _________ galaxy.

Milky Way, Spiral

How many black holes are there in our galaxy?

Millions

Hubble took spectra of galaxies in the 1930's. What did he find?

Most galaxies showed red shifts.

When a Super Giant explodes it leaves behind a _________ star. If this super-dense star continues to collapse it will form a _________________ .

Neutron, Black Hole

Why doesn't our galaxy's super-massive black hole have jets coming from it?

Not enough matter around it.

What would change if our Sun was suddenly replaced by a black hole of the same mass?

Only the temperature on Earth would change.

Most of the galaxies (99%) are...

Rushing away from us.

_______ galaxies may bridge the gap between spiral galaxies and quasars.

Seyfert

Center of a black hole.

Singularity

The gravity of a black hole is so strong because of its small _____ and large _______.

Size, Mass

How would the motion of stars at the edge of our Galaxy be different if there were no dark matter present? In the absence of dark matter, the stars most distant from the galactic center should be moving much __________________ than those stars orbiting closer to the center.

Slower

What would happen to your body as you fell into a normal sized black hole?

Spagettified-body super stretched, killing you.

A galaxy containing substantial amounts of dark matter will?

Spin Faster

Which type of galaxy most resembles our Milky Way?

Spiral

Galaxy with flattened galactic disk in which spiral arms are found, a central galactic bulge with a dense nucleus and an extended halo of faint, old stars.

Spiral Galaxy

Galaxy undergoing an exceptionally high rate of star formation because of an interaction with another galaxy.

Starburst Galaxy

We can't see normal black holes, so how do we know they exist?

Stars orbiting around nothing.

What happens to matter as it falls into a black hole?

Swirls around the BH like a whirlpool.

Galaxy distance and Doppler red-shift are correlated for galaxies. What do we call that correlation?

The "Hubble Law"

Where would you find the brightest part of a galaxy? WHY?

The center.

What did the discovery suggest to cosmologists?

The universe is expanding.

Hubble's spectra of galaxies in the 1930s showed that most galaxies are redshifted. What does this mean?

The universe is expanding. Galaxies are moving away from us.

Black holes are invisible because they don't reflect light.

True

It is now believed the majority of mass for most galaxies lies in their dark halos.

True

What are the differences between an Sa galaxy and an Sc galaxy? What about an E0 and an E7?

Type Sa has the largest central bulge and type Sc is the smallest. E0 are almost spherical, while E7 are the most elongated.

Where do black holes come from?

When a star dies it collapses and turns into a supernova.

What about going into a Super-Massive black hole?

You could go in a ways, then see blinding light, then vaporize.

Galaxies evolve by?

merging to form larger galaxies.