Astr311 Final

Created by tujoyous 

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A nova involves

Mass transfer onto a white dwarf in a binary star system

A white dwarf can explode when

Its mass exceeds the Chandrasekhar limit (Max mass a white dwarf can be)

A type II supernova occurs when

Iron builds up in the core

Supernova 1987A was important because

Its parent star had been studied before the explosion.
Its distance was already known.
It was observed early as its light was still increasing.
Its evolution was captured with detailed images from the Hubble Space Telescope

Some examples of which type of dying star exhibit rapid pulses that were originally suspected to be communications from extraterrestrials?

Neutron Star

Average density of neutron star approaches

About 10^17 kg/m. Similar to the density of an atomic nuclei

Pulsars usually show what characteristics?

Extremely rapid rotation, a narrow regular pulse of radiation, high speed motion through the galaxy, and an intense magnetic field.

NOT: high temperature fusion reactions (cause no fuel, so no fusion reaction)

the lighthouse model explains how:

A rotating neutron star generates an observable beam of light

Many millisecond pulsars lie within

globular clusters

The event horizon of a black hole is measured by...

the Schwarzchild radius

What happens if the sun was replaced by a one-solar mass black hole?

Earth's orbit would not change

One possible explanation for a gamma-ray burster is

the collision of neutron stars in a binary system

In contrasting the distribution of the x-ray and gamma-ray bursts, we find that...

Gamma ray bursts are far beyond our galaxy at cosmological distances and spread all over the sky, not in the plane of our galaxy

In structure, our Milky Way is most similar to...

M-31, the Andromeda Galaxy

The part of the Milky way we are most familiar with is

The galactic disk

For what type of object is the period-luminosity relation used for determining distances?

Cepheids

Based on our star counts, 100 years ago, most astronomers thought...

We lay near the center of a disk about 10 kpc wide and 2kpc thick

The location of the galactic center was first found by Harlow Shapely with...

RR Lyrae variables in the globular clusters

What is the correct description of the Sun's location within the Milky Way?

Above the disc and about one-third of the galactic radius from the center

Why was Hershell's strategy for mapping our galaxy flawed?

He relied on visual wavelengths, which are obscured by dust

Herber Curtis was correct in arguing that the Milky Way was...

Similar to spiral nebulae.
Blocking our view of spiral nebula in the galactic plane

Harlow Shapely was correct in arguing that the Milky Way was

Much larger than previously thought

The region on the HR diagram where pulsating variables occur is called the

Instability strap

All RR Lyrae stars have about the same

Luminosity of about 100 suns

Which of the following are most massive and luminous?
A) Brown dwarfs
B) RR Lyrae variables
C) White Dwarfs
D) T-Tauri variables
E) Cepheid variables

E) Cepheid variables

A star in the instability strip of the HR diagram would

Vary in both temperature and radius

Most of the new star formation in the Galaxy (Milky Way) is found in the

Spiral arms

The orbits of population II stars have been compared to

Comets around the sun

What is the galactic year?

The time for our solar system to orbit the galaxy

How long is a galactic year?

225 million years

Detailed measurements of the disk and central bulge region of our Galaxy suggests our Milky way is a

Barred spiral galaxy

The "aspect ratio" of thickness to width of the galactic disk is about

1:100

Which sequence of formation by age is correct, oldest to youngest?
A) Dark nebulae, planetary nebulae, emission nebulae
B) Spiral arms, bulge, halo
C) Halo, Spiral arms, globular clusters
D) Globular clusters, emission nebulae, open clusters
E) Population I stars, Population II stars, Population III Stars

D) Globular clusters, emission nebulae, open clusters

What are 21cm radio waves to galactic astronomers?

Their Doppler Shifts let us map the motions and locations of gas in the spiral arm

The leading explanations for the existence of spiral arms are

Passages of spiral density waves through the interstellar medium

Which of the following is most like the rotation of stars in the disk of the milky way?
A) A DVD in a player
B) planets in our solar system
C) Cars moving at a constant speed on a circular race track
D) the hands of an analog clock
E) the tire of a car moving

C) Cars moving at a constant speed on a circular race track

What two observations allow us to calculate the Galaxy's mass?

The Sun's orbital velocity and its distance from the galactic center

What observations suggest the mass of the Galaxy goes much farther out than its visible disc?

Rotation curve of the outermost portions of the disc

Which method relies on the mass of a dark object revealing its presence?

Temporary brightening of distant star by a gravity lens

Most of the mass in the Milky way seems to exist in the form of

Dark matter out in the Halo

While yet unproven, the proposed WIMPS could be

massive like neutrons, but more elusive than neutrinos

The Radio source ____ located in a place consistent with the center of our galaxy

Sgr A*

A spherical galaxy, like M87, which looks like a monster globular cluster is a type:

E0

The flattest of the ellipticals are class

E7 (E9 is not possible. Any flatter than E7, then its not an elliptical galaxy)

Which type of galaxy has a stellar disk but without gas and dust?

S0

You observe a spiral galaxy with a large central bulge and tightly wrapped arms. It would be classified as

Sa

An intermediately wound barred spiral galaxy would, in Hubble's system be

SBb.

In hubble's classification, which type of galaxy has small bulge and loose widely spread, poorly defined spiral pattern?

Sc. (a, b, c class....big to small bulge)

Which type of galaxy has no stellar disk, and no gas or dust?

E0 (elliptical galaxies don't have disks, very little gas and dust. E9 not a possible galaxy because its not stable)

Which of the following is true about the ages and masses of spiral and elliptical galaxies?
A) ellipticals are all older and more massive than spirals
B) Spirals are older and much more massive than ellipticals
C) Both types are about the same age, but spirals vary less in mass
D) Spirals are younger and much more massive than any ellipticals
E) Ellipticals are older, and show a far wider range of masses than do spirals

C) Both types are about the same age, but spirals vary less in mass

Which of these would be made up of only population II stars?
A) elliptical galaxies
B) Irr Type I
C) Irr Type II
D) barred spirals
E) Seyfert Spirals

A) elliptical galaxies

Most of the galaxies in the Local Group are

Small ellipticals like the companions to M31 in the Andromeda galaxy

Most of the stars in the Local group are

Big spirals like our Galaxy and M31

Within the Boundaries of the constellations Coma and Virgo, are found

The largest nearby superclusters of galaxies

Why does the Cepheid "standard candle" have limited usefulness beyond 20 Mpc?

Cepheids are too faint to be seen beyond that distance, even with HST

What is hubble's law?

The greater the distance to a galaxy, the greater the red shift

The Tully-Fisher relation exists between the galaxy's luminosity and its:

Rotation

For finding the distance the M31, Hubble reled on

Cepheids variables in its spiral arms

While examining the spectrum of a galaxy, you find all the hydrogen lines are shifted to longer wavelengths, this galaxy is:

Moving away from us.

What are in Seyfert galaxies

Always spiral galaxies. And change luminosity very rapidly (much faster/brighter than stars)

quasars usually have their distances measured by what technique?

Hubble's Law

Why do some quasars have redshifts greater than 1?

Very distant, with relativistic red shifts that take into account of dilation of space time, as Einstein predicted

The quasars were at cosmological disks yet appear like faint stars, what does this mean?

they must be producing such large quantities of energy than even fusion that even fusion could not explain their output

In active galaxies, their central engine must be temporarily fed by

Close encounter with a neigbour galaxy

A billion solar mass black hole would still have a radius of only

20 AU

Synchrotron radiation produces a _____ spectrum

Continuous non-thermal

The energy radiated by a typical quasar requires that its black hole accrete about:

10 solar mass a year

rotation curves for spiral galaxies show

most have dark halos

How massive are the largest known galaxies

A trillion solar masses

As we look at larger and larger scales in the universe, we find
A) smaller and smaller masses
B) almost exclusively visible matter
C) a larger and larger % of the matter is visible
D) a larger and larger % of the matter is dark
E) an equal amount of visible and dark matter

D) a larger and larger % of the matter is dark

Based on galactic rotation curves and cluster dynamics, we think dark matter:

comprises over 90% of the matter in the universe

A radio galaxy whose lobes are swept back as if its forming a tail. This probably indicates that:

Evidence for intergalactic matter

The distance between adjacent galaxies in the atypical cluster is about ____ times the size of a typical galaxy

5 or fewer

Collisions between galaxies are thought to:

be commonplace

Which of these is NOT considered a fine example of galactic collision?
A) the cartwheel galaxy
B) the Antennae galaxies
C) the Whirlpool galaxy
D) M-31 in Andromeda
E) M-87 in Virgo

D) M-31 in Andromeda

When spiral galaxies do collide, the impact is greatest on their

Giant molecular clouds

Due to the galaxy density and collisions, _____ are rare in the centers of clusters

Spirals

The pregalactic blobs had masses similar to

Large Magellanic cloud

Why are supermassive galaxies often found at the cores of rich galaxy cluster?

They are the result of many galactic mergers; one galaxy growing at the expense of others

Some quasars show absorption spectra with a smaller redshift than their emission spectra, this indicates that

There is cooler gas between us and the quasar

Astronomers think most galaxy interactions took place at redshifts of greater than 1 because

Clusters were more compact

Why is thought that quasars probably spend only a fairly short time in their highly luminous phase?

Because a black hole could not power a highly luminous quasar for more than a few million years

The energy radiated from a typical quasar requires that its black hole accrete about

10 solar masses/year

Careful observations of nearby normal and active galaxies reveal that the mass of the central black hole is well correlated with the mass of the galactic bulge. The ratio of bulge mass to black hole mass is roughly:

200 to 1

What is the Great Wall?

It is a large sheet of galaxies measuring 70 Mpc by 00 Mpc

Gravitational lensing of distant, faint irregular galaxies may be the key to

Mapping the dark matter

Homogeneity and isotrophy, taken as assumptions regarding the structure and evolution of the universe, are known as

The cosmological principle

The Hubble time is expressed as:

1/H

The redshift of the galaxies is correctly interpreted as

Space itself and expanding with time, so photons are stretched while they travel through space

What does the Hubble law imply about the history of the universe?

Universe had a beginning and has expanded since, giving it a finite age

Why is the sky dark at night?

Because all light from all objects in universe hasn't arrived yet

What is the big bang?

Event that started expansion of the universe

If the density of the universe is greater than the critical density this means that

Universe is expanding at rate less than escape speed of universe

In the closed universe model, the geometry of spacetime in two dimensions resembles the surface of a

sphere

In robert's frosts' classic poem, when he ends with "ice will suffice" the universe is

open

In a closed universe a beam of light will

come back to where it originated

The critical evidence for cosmic acceleration in 1998 came from two teams of astronomers, both observing

type I supernovae

The universal accelerating force could NOT be considered
A) Antigravity
B) Einstein's cosmological constant
C) dark energy
D) Vacuum pressure
E) dark matter

E) dark matter

Matter made out of protons, neutrons, and electrons in the universe accounts for what percent of the total mass of the universe?

less than 4%

IN the critical density universe now proposed, the ratio of dark energy to matter is about

3 to 1

In our best current theory, the first quasars formed about

13 billion years ago

According to the turn-off points of the oldest globular clusters, they about about

12 billion years old

The discovery of the cosmic microwave background was important because

it was experimental verification of a predication from Big Bang theory

What temperature has the Big Bang cooled to by now?

just over 2.7 K

The photons from the microwave background have not interacted with matter since the universe was how old?

400,000 years old

When the microwave background radiation was emitted, about how big was the universe?

1/1000 its current size

The Wilkinson mapping project gave:

omega0 = 1, but matter (dark and visible) is only 27% of this, the rest is dark energy

How does the energy of the cosmic microwave background compare to the energy radiated by all the stars and galaxies that ever existed?

About 10 times more from the Big Bang than from stars and galaxies

At this time, the universe is
A) radiation dominated
B) quark dominated
C) lepton dominated
D) matter dominated
E) dark energy dominated

E) dark energy dominated

Before about 4 billion years ago, the universe was
A) radiation dominated
B) quark dominated
C) lepton dominated
D) matter dominated
E) dark energy dominated

D) matter dominated

Before about 50,000 years after the Big Bang, the universe was
A) radiation dominated
B) quark dominated
C) lepton dominated
D) matter dominated
E) dark energy dominated

A) radiation dominated

In the process of pair production, which of the following is a possible product pair?
A) electron-neutron
B) proton-neutron
C) electron-positron
D) proton-positron
E) electron-proton

C) electron-positron

Because of their mass, the threshold temperature for electrons is

lower than that of protons

How hot was the universe at time zero?

no theory capable to address this question

Gravity becomes separate from other forces at the

End of the Planck Era, about 10^-43 seconds after the Big Bang

Collectively electrons, muons, and neutrinos are called

Leptons

The quark epoch is when ____ was/were created

protons and neutrons that still survive

Of the normal elements around us, the Big Bang produced

Hydrogen and helium

At the end of the first 15 minutes, the mass ratio of Hydrogen/Helium created was about

75/25

The scarcity of what isotope is a critical test of the density of the present cosmos?
A) carbon 14
B) deuterium
C) helium 3
D) helium 4
E) lithium 5

B) deuterium

About how hot was the Big Bang when matter and energy "decoupled"?

3000 K

What did the cosmic microwave background tell cosmologists about early universe?

The horizon problem in that the microwave background is too isotrophic

The best answer to both the flatness and horizon problem is

Inflationary epoch

Which of these could be considered as "hot dark matter"?
A) Deuterium
B) Weakly interacting magnetic particles (WIMPS)
C) Neutrinos
D) Dust close to H II regions
E) dark energy

C) Neutrinos

What important molecules of life did MIller And Urey brew up?

Amino acids

A similar experiment was more recently done by NASA using an icy mixture of water, methanol, ammonia, and carbon monoxide. The mixture was exposed to UV radiation. Results of this experiment were that no amino acids or DNA was formed, but complex organic molecules were observed. Purpose of this experiment was to determine whether...

Amino acids could form in the harsh vacuum of outerspace

The simplest life forms appeared on Earth when it was how old?

1 billion years old

How long between the evolution of single versus multicellular organisms?

2.5 billion years

The famed meteorite with carbonate rocks and possible microfossibles came from

Mars

For which of these forms of life is it hardest to apply present criteria for life, based on its behaviour when isolated?

A virus

Why is the hypothesis that life on Earth came from outer place considered plausible?

Because many meteorites contain complex organic molecules

What was the Viking, pathfinder used for?

All designed to investigate life

What are extremophiles?

they can create their own energy through chemical reaction and live in environments previously thought too alkaline, hot, cold, dark, saline, etc to sustain life.

Assuming conditions for life and intelligence abound in galaxy, what factor limits the number of galactic civilizations?

average survival time of the civilizations

According to our definition we have been a technological civilization for about

100 years

Why do we feel type O and B stars are poor candidates for extraterrestrial life?

LIfetime too short

What is habitable zone?

Region around each star where terrestrial planets could have liquid water on their surfaces

Which stars would be good candidate for seeking extraterrestrial intelligence?

61 Cyngi, a K2 main sequence star

First probe carrying mankind's message to alien civilizations was

Pioneer 10

Most of the energy of the supernova is carried outward via a flood of

Neutrinos

A 20 solar mass star will stay on the main sequence for 10 million years, yet its iron core can exist for only a

day

As a star's evolution approaches the Type II supernova, we find
A) photodisintegration of iron nuclei begins at 10 billion K to ignite the supernova.
B) the heavier the element, the higher the temperature to fuse it.
C) helium to carbon fusion takes at least 100 million K to start.
D) the heavier the element, the less time it takes to make it.
E) all of the above are correct

E) all of the above are correct

Characteristics of Type I supernova

Low mass star, carbon-detonation supernova, hydrogen-poor

Characteristics of Type II supernova

High mass star, Core-collapse supernova, hydrogen-rich

Radius of a white dwarf is determined by a balance between the inward force of gravity and the outward push of what?

Electron degeneracy pressure

What occurs when hydrogen fusion ignites on the surface of a white dwarf in a binary system?

A nova

What occurs when fusion creates iron in the core of a star?

A massive star supernova

A white drawf in a close binary system will explode as a supernova if it gains enough mass to exceed the _____

White dwarf limit (1.4 solar masses)

What consists of hot, swirling gas captured by a white dwarf (or neutron star in black hole) from a binary companion star?

An accretion disk

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