ASTRO Final

Stars in a star cluster

-all have the same age. -all have the same chemical composition. a and b above

The look-back time is

-the time it takes for the light from an object to reach Earth. -numerically equal to the distance in light-years. a and b above

Active galaxies are notable because they are point sources that emit extremely energetic streams of

-gamma ray photons -x-ray photons Either a. or b.

The Milky Way Galaxy is a spiral galaxy with a disk shape whose dimensions are

100,000 light years across and several thousand light years thick

About how far can we see before intstellar dust begins to block our view of the stars?

1000 light years

What distance method is used to determine the distance to the most distant galaxies?

Supernova observations

When galaxies collide, what is the most likely outcome?

They will eventually merge to form a single galaxy

A spiral galaxy can grow by

absorbing smaller galaxies

The energy from an AGN is produced by

matter flowing into a supermassive black hole.

A quasi-stellar radio source is now more commonly called a

quasar

A(n) ____ emits large amounts of energy but photographically appears to be a single point of light much like a star.

quasar

In 1920, the Great Debate was an argument about whether the the Milky Way was the entire universe, or if the Milky Way was one of many similar type of objects. Who was the astronomer who argued that the Milky Way was all there is?

Harlow Shapley

Younger stars have more heavy elements because

the heavy elements were made in previous generations of stars.

Galactic cannibalism refers to

the merging of galaxies.

Supermassive black holes are believed to be located at the center of many galaxies because

the orbital motion of material near the center is very fast and indicates a very massive core.

If we reverse the expansion of the universe and ask when all of the material in the universe was in the same location, the age of the universe can be determined. According to Phil the current, best estimate for the age of the universe is (the value has been updated slightly since the video was recorded but is close to this value)

13.82 Billion years

At the center of the Milky Way Galaxy is a supermassive black hole with a mass of

4 Million Solar Masses

About how long will a 0.5 star spend on the main sequence?

57 billion years

___________ can be used to determine the galaxy's mass if the galaxy is reasonably close so that the Doppler shift of the galaxy disk material can be measured at several distances from the galaxy's center relative to the center.

A galaxy's rotation curve

Pulsating stars, that change their brightness with a regular period are known as ____________. They were important for determining the distance to galaxies because their period is related to their luminosity (L).

Cepheid variables.

These galaxies are characterized by a lack of gas and dust and are primarily made of older stars. They range in size from a few thousand light years across to vastly larger than the Milky Way.

Elliptical

According to Phil, where is the center of the universe?

Every point in the universe looks like the center, so no point is actually the center of the universe

How is the age of the galaxy determined?

Finding the turnoff point in the H-R diagram of globular clusters.

If Galaxy A is found to have a recessional velocity four times greater than Galaxy B, what can you say about their relative distances from Earth?

Galaxy A is four times further away than Galaxy B.

When ancient people looked up at the Milky Way, they saw a glow that looks like a nebula. Which of the following astronomers looked with a telescope and descovered that the Milky Way is made of countless stars, so close together that they could not be seen as separate with the naked eye.

Galileo Galilee

This scientist was the first to declare that the universe was NOT static and unchanging, but either expanding or contracting.

George Lemaitre

The orbits of population I stars I. are confined to disk of the galaxy. II. are very elliptical. III. are nearly circular. IV. are randomly inclined to the disk of the galaxy.

I & III

Population II stars I. are primarily found in the disk of the galaxy. II. contain more heavy metals than population I stars. III. are primarily old low mass stars. IV. are located in globular clusters.

III & IV

Where would you find the Milkomeda Galaxy?

It doesn't exist yet. It will be the galaxy that forms when the Milky Way and Andromeda Galaxies merge

The small cluster of galaxies that the Milky Way is a part of (a few dozen in all) is known as the

Local Group

Which of the following can't be associated with the spiral arms of a galaxy?

Metal poor stars

The Greek word Galaxius means

Milky

What is the universe expanding into?

Nothing, it is creating spacetime as it expands

Our sun is thought to be on a small projection from one of the major arms of the Milky Way Galaxy, called the

Orion Arm

These galaxies have odd or distorted shapes and are all due to collisions between galaxies that are still occuring.

Peculiar

Clusters of galaxies clump together to form larger structures known as ________________ which are held together by their mutual gravitational attraction.

Superclusters

Where are elements heavier than iron primarily produced?

Supernovae

____ is a form of electromagnetic radiation produced by rapidly moving electrons spiraling through magnetic fields.

Synchrotron radiation

Which of the following is the largest object?

The Local Group.

What is the Hubble constant essentially a measure of?

The expansion of the universe.

The astronomer named Vesto Slipher who according to Phil has the "uncontested, coolest name for an astronomer", began in 1912 abserving the spectra of spiral galaxies and by 1917 had observed 25 of them. What was the remarkable discovery that he made?

The galaxies were highly red shifted indicating the galaxies were rapidly moving away from our galaxy.

____ of the Milky Way contains mostly old (population II) stars and globular clusters.

The spherical halo component

How does the traditional theory of the formation of the galaxy explain the origin of globular clusters?

They formed early on during the free-fall collapse of the proto-galactic material.

All of the following are types of galaxies except

Toroidal

What nuclear fusion mechanism does an isolated white dwarf use to generate energy?

White dwarfs don't generate their own energy.

The Tarantula Nebula is forming so many stars that astronomers think it may be forming

a globular cluster

A mega-parsec is equivalent to

a million parsecs.

The supermassive black hole at the center of the Milky Way does not appear to be emitting light but is virtually invisible to us. This black hole without an accretion disk is called

a quiescent black hole

The explosion of a supernova typically leaves behind

a shell of hot, expanding gas with a pulsar at the center.

A Type I supernova is believed to occur when

a white dwarf exceeds the Chandrasekhar limit.

According to Phil, our solar system is located

about 1/2 of the way from the center to the edge of the Milk Way

A region near a black hole has matter orbiting the black hole at nearly the speed of light and is heated from friction and other interactions. This region is reaches temperatures of millions of degrees and consequently emits a huge amount of light across the spectrum.

accretion disk

A group of 10 to 100 stars that formed at the same time but are so widely scattered in space their mutual gravity cannot hold them together is called

an association.

In the 1960s the object known as 3C273 appeared with optical telescopes to be a dim blue object, but extremely bright in the radio part of the spectrum. It was determined from its spectra to be a

an entire galaxy more than 2 billion light years away

Two huge, looping streams of stars circling the Milky Way are probably part of the Sagittarius and Canis Majoris galaxies

being eaten by the Milky Way

Massive stars cannot generate energy through iron fusion because

both fusion or fission of iron nuclei absorb energy

The study of the large scale structure of the universe is called

cosmology

Most of the mass of a galaxy is contained in the

dark matter of the galaxy.

The Hubble Law is a relation between a galaxy's

distance and its recession velocity.

The region surrounding the Milky Way out to about 100,000 light years is made up of old, stable red dwarf stars and NO star-forming regions is called

the halo

Measuring the Doppler shift of radio waves emitted in a narrow band by young star-forming regions allowed us to "see" that the Milky Way

has spiral arms

Which of the following nuclear fuels does a one solar mass star use over the course of its entire evolution?

hydrogen and helium

The chemical abundance of population I stars

indicates that the material they formed from had been enriched with material from supernovae.

The Hubble "Deep Field" image was taken in the 1990s of one of the darkest areas of the sky. It observed a small spot of the sky about 2.6 arcminutes on a side (about the size of a grain of sand held in your hand at arm's length) and took a picture over the course of ten days. When the picture was analyzed they found

it contained thousands of galaxies

As we observe more and more distant objects, the time the light takes to get to us is longer and longer. This means that we are seeing the object as it appeared in the past. The astronomical term for this is

lookback time

The Big Bang must have been very hot, so hot that there would be a lot of visible light produced. Because of the expansion of the universe, this visible light has been red shifted to the ______________ range of the electromagnetic spectrum. Penzias and Wilson were awarded the Nobel prize in physics (1978) for their serendipitous discovery of this radiation in 1965.

microwave

Which of the following elements were created in the Big Bang?

mostly hydrogen and helium (75% H and 25% He)

The age of the Milky Way galaxy has been estimated to be at least 13 billion years based on

observations of globular clusters.

Gravitational lensing

occurs when light passes near a massive object and is deflected by the object's gravitational field.

If the theory that novae occur in close binary systems is correct, then novae should

repeat after some interval.

The Large Magellanic Cloud and Small Magellanic Cloud are considered _______________ of the Milky Way Galaxy.

satellite galaxies

What do astronomers now think powers active galaxies?

supermassive black holes

The Crab nebula is

supernova remnant.

The Milky Way galaxy is part of

the Local Group.

The theory that the collapse of a massive star's iron core produces neutrinos was supported by

the detection of neutrinos from the supernova of 1987.

The period-luminosity relation is useful in determining

the distance to globular clusters that contain Cepheid variables.

A planetary nebula is

the expelled outer envelope of a medium mass star.

Edwin Hubble and (partner) carefully studied the galaxies that had been studied by Slipher and concluded that the further away a galaxy was from us,

the faster it was receding from us.

Most of the globular clusters in the Milky Way are found in

the galactic halo

The Chandrasekhar limit tells us that

white dwarfs more massive than 1.4 solar masses are not stable.