281 terms

Astr311 Final

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?
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
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:
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?
You observe a spiral galaxy with a large central bulge and tightly wrapped arms. It would be classified as
An intermediately wound barred spiral galaxy would, in Hubble's system be
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:
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
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:
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
In robert's frosts' classic poem, when he ends with "ice will suffice" the universe is
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
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
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
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
A 20 solar mass star will stay on the main sequence for 10 million years, yet its iron core can exist for only a
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
What can occur only in a binary system, and all such events are thought to have the same luminosity?
A white dwarf supernova
In a neutron star, the core is
made of compressed neutrons in contact with each other.
An object more massive than the Sun, but roughly the size of a city, is a
neutron star.
What would happen if mass is added to a 1.4 solar mass white dwarf?
The star would erupt as a carbon detonation (type I) supernova
Which of these does not exist?
A) a million solar mass black hole
B) a 6 solar mass black hole
C) a 6.8 solar mass neutron star
D) a 1.0 solar mass white dwarf
E) a 0.06 solar mass brown dwarf
C) a 6.8 solar mass neutron star
The most rapidly "blinking" pulsars are those that
spin fastest
X-ray bursters are similar to novae, except the collapsed star is a neutron star, not a white dwarf (T/F)
Three terrestrial-sized planets in orbits of a fraction of an AU have been found near
a millisecond pulsar
What are X-ray bursters?
they are neutron stars on which accreted matter builds up, then explodes in a violent nuclear explosion.
Almost half of all known millisecond pulsars are found in what type of object
globular clusters
To which of these phenomena are X-ray busters most similar?
Gamma-ray bursts are observed to occur
approximately uniformly over the entire sky
A proposed explanation for gamma-ray bursters is
A) hypernova-making black holes and bi-polar jets.
B) coalescence of a neutron star binary.
C) collisions between two white dwarfs.
D) Both A and B are possible.
E) All three are possible.
D) Both A and B are possible.
Put these in largest to smallest diameter:
-One-solar mass white dwarf
-Main sequence star of spectral type A
-Event horizon of a two-solar mass black hole
-The moon
-a two-solar-mass neutron star
Main sequence star, jupiter, one solar mass white dwarf, moon, two solar mass neutron star, even horizon
Put these in largest to smallest MASS
-One-solar mass white dwarf
-Main sequence star of spectral type M
-Typical black hole (formed in a supernova)
-The moon
-typical neutron star
Black hole, neutron star, white dwarf, type M main sequence, jupiter, moon
Put these in largest to smallest DENSITY
-One-solar mass white dwarf
-Main sequence star
-Typical black hole (formed in a supernova)
-typical neutron star
Black hole, neutron star, white dwarf, main sequence star
Characteristics of a white dwarf
mass no greater than 1.4 solar mass
in a binary system, can explode as supernova
supported by electron degeneracy pressure
Typically about size (diameter) of Earth
characteristics of neutron star
Sometimes appears as a pulsar
usually has very strong magnetic field
Black holes result from stars having initial masses
more than 25 times the mass of the Sun.
review 21, 22,23 of 23 , mastering 8
Listed following are several locations in the Milky Way Galaxy. Rank these locations based on their distance from the center of the Milky Way Galaxy, from farthest to closest.

-Our solar system
-A cloud of gas and dust in the outskirts of the disk
-The edge of the Central bulge
-A globular cluster in the outskirts of the halo
Globular cluster, cloud of gas and dust, solar system, edge of central bulge
Imagine a photon of light traveling the different paths in the Milky Way described in the following list. Rank the paths based on how much time the photon takes to complete each journey, from longest to shortest.

-from sun to the center of galaxy
-through the disk from top to bottom
-across diameter of galactic halo
-across diameter of central bulge
-across diameter of galactic disk
Across diameter of galactic halo, across diameter of galactic disk, from sun to center of galaxy, across diameter of central bulge, through disk from top to bottom
Characteristics of disk stars (yellow)
Youngest stars, the sun, stars that all orbit in nearly the same plane, high-mass stars
Characteristics of halo stars (green)
Oldest stars, stars whose orbits can be inclined at any angle, stars with smallest abundance of heavy elements, globular clusters
The circular but relatively flat portion of the galaxy is the ____
The first portion of the galaxy to form was the ____
A tightly packed group of a few hundred thousand very old stars is a _____
globular cluster
a ____ stands out in a photo of a galaxy because it shines brightly with light from massive young stars and glowing clouds of gas and dust
Spiral arm
Our milky way galaxy is a ____
spiral galaxy
Stars orbiting in the ____ near the galaxy's center can have orbits highly inclined to the galactic plane
The first stars that formed in the Milky Way now
have random orbits in the halo.
Population I stars came billions of years before Population II stars (T/F)
In our vicinity, the galactic disk is about 100 times wider than it is thick.(T/F)
Most of the new star formation in the Galaxy is found in the
spiral arms
Matter belonging to the Galaxy can be traced out to ________ from the center.
50 kpc
The orbits of Population II stars have been compared to
comets around the Sun
From the Sun, the distance to the Galactic Center is about
8,000 pc.
The Galactic Year is the time for our solar system to orbit the Galaxy; it is about
225 million years
From Earth, the view of the Milky Way is a thin band of stars across the night sky. The part of the Milky Way galaxy that is described here is the
Where are large dust clouds predominantly located in the galaxy M51?
within or on the edges of the spiral arms
Where are the ionization nebulae predominantly located in the galaxy M51?
within or on the edges of the spiral arms of the galaxy
Why are the ionization nebulae so bright?
They are regions where gas is ionized by hot, young stars.
A telescope searching for newly formed stars would make the most discoveries if it were pointed
within a spiral arm.
Rank the following based on least curvature to greatest curvature

Main sequence star
Neutron star
Red dwarf
Black hole
White dwarf
Red giant, main sequence star, white dwarf, neutron star, black hole
Rank the following based on amount that each would deflect the path of a photon of light from a very distant galaxy. From smallest amount to largest amount

Main sequence star
Neutron star
Red dwarf
Black hole
White dwarf
Red giant, main sequence star, white dwarf, neutron star, black hole
Characteristic of elliptical galaxy (E)
Round, no disk, very little gas and dust, only old stars
Characteristic of spiral galaxy (S)
Central bulge, flattened disk, spiral arms, gas, dust, young stars
Characteristic of Barred-spiral galaxy (SB)
Elongated central structure, flattened disk, spiral arms, gas and dust, young stars
characteristic of irregular galaxy (Irr)
Asymmetric, often with gas, dust and young stars
The irregular classification is in some ways a method of dealing with galaxies that are clearly not elliptical or spiral in shape. Select the properties associated with irregular galaxies
Exhibit vigorous star forming activity
Some show evidence for prior collision or close encounter with another galaxy
They are typically smaller than spiral galaxies
What galaxy has little star forming activity? What galaxy has significant star forming activity?
Little: elliptical
Significant: Irr, spiral, barred spiral
relationship between distances of galaxy and the speed in which they should be moving away from earth due to expansion of universe?
Hubble's law says that the more distant a galaxy is from earth, the faster it is moving away from us. The greater the distance, the faster they are moving away.
Relationship between speed at which galaxies are moving away from earth due to expansion of the universe and how far that galaxy is from earth
Hubble's law says a more distant galaxy move at higher speeds
Relationship between speed of galaxies moving from earth due to expansion of the universe and the amount of redshift observed in each galaxy's spectrum, from largest to smallest.
The greater the speed/faster, the larger the redshift. This is because redshift tells us that an object is moving away from us, and the larger the redshift, the higher the speed.
Looking at a graph (distance on x-axis and speed on y-axis) what does a steeper line mean in terms of speed? (hubble's law)
Steeper slope for hubble's law would predict faster speeds for galaxies at particular distances
Looking at a graph (distance on x-axis and speed on y-axis) what does a steeper line mean in terms of age of universe?
The steeper the slope, the more rapid the rate of expansion and the more rapid the rate of expansion, the younger the universe
The graph shows that galaxies with high speeds as measured from Earth are __________.
moving away from Earth and are farther from Earth than galaxies with lower speeds. (more distant galaxies are moving away from us faster)
By looking at the graph, what can we say about the galaxies that have the lowest speeds?
They are moving away from Earth and are closer to Earth than galaxies with high speeds.
Suppose that galaxy B is twice as far from Earth as galaxy A. Hubble's law predicts that galaxy B will be moving away from Earth with approximately _____.
twice the velocity of galaxy A
Imagine that when we looked out into the universe we found that the light from all galaxies was blueshifted (rather than redshifted) and that the light from the most distant galaxies was blueshifted by the greatest amount. Which statement best describes what we would conclude about the motions of galaxies in this case?
All are moving toward Earth, with distant galaxies moving faster than nearby galaxies
The age of the universe is related to the slope of the graph of Hubble's law, and current data put the age of the universe at about 14 billion years. Suppose that future observations showed that the slope of Hubble's law on the graph is actually steeper than that shown. In that case, the age of the universe would be _________ than 14 billion years because the universe is expanding ______ than current data suggest. (Each choice gives words to fill in the two blanks, separated by a slash.)
younger / more rapidly
Our entire solar system orbits around the center of the ______ about once every 230 million years
Milky way Galaxy
The milky way and andromeda galaxies are among a few dozen galaxies that make up our __________
Local Group
the sun appears to rise and set in our sky because Earth ____ once each day
You are on year older each time Earth _____ about the sun
On average, galaxies are getting farther apart with time, which is why we say our ________ is expanding
Our ________ is moving toward the star Vega about 70,000 km/hr
Solar system
Why do astronomers hypothesize that a massive black hole lies at the center of M 87?
A very small region at the center of M 87 releases an enormous amount of energy.
Assuming that the bright core of M 87 is powered by a supermassive black hole, which of the following best describes the source of energy that makes the core appear so bright?
Gravitational potential energy is converted to thermal energy as matter from the surrounding gas disk spirals into the central black hole.
What radiation is emitted from:
-Dusty donut
-Supermassive black hole
-Acccretion disk
-Magnetized jet
Donut: infrared
Black hole: none
Accredtion: X-ray
Jet: radio
Characteristic of Thermal Radiation
It peaks at a characteristic frequency. Its radiation depends on the temperature of the source
Characteristic of Synchotron radiation
Its radiation is consistently stronger at lower frequency (longer wavelength). Its radiation depends on the presence of magnetic fields.
What conclusions can be drawn about the nature of the galaxy cluster's mass?
Most of the cluster's mass cannot be seen as visible matter. the mass of the dark matter accounts for more of the gravitational force within the cluster than does the mass of the visible matter.
Rank the following items according to their size (diameter) from largest to smallest
-Milky way galaxy
-The universe
-The Sun
-Local group
-The earth
-The local supercluster
-Our solar system
Universe, local supercluster, local group, milky way galaxy, our solar system, the sun, jupiter, earth
Rank the following items from longest distance to shortest distance.
-One light year
-Distance from the Milky way Galaxy to the Andromeda Galaxy
-One astronomical unit (AU)
-Distance from earth to Alpha Centauri
-Distance from sun to the center of the Milky Way Galaxy
-The average distance from Earth the Sun
-Distance across our solar system (to Neptune)
The distance from milky way galaxy to andromeda galaxy, distance from sun to center of milky way, distance from earth to alpha centauri, one light year, distance across solar system, 1au=average distance from earth to sun
What are some single astronomical objects?
Star, planet, comet
What are some collections of astronomical objects?
Solar system, milky way galaxy, galaxy, supercluster
What do astronomers believe is the result of a merger between two spiral galaxies?
An elliptical galaxy
A head-tail radio galaxy is one that has ______ significantly while ejecting its radio lobes.
What is the defining characteristic of starburst galaxies?
They have a large number of young stars.
Intracluster gas has been observed in what region of the spectrum?
Which galaxies are relatively rare in regions of high galaxy density?
How many years ago did most quasars became inactive?
10 billion
What is the average distance between adjacent galaxies in a galactic cluster?
A few hundred thousand parsecs
Which law is used in the calculation of the combined galaxy masses of a binary galaxy system?
Newton's form of Kepler's third law
What is unusual about the results of mass determinations of clusters of galaxies
There is much more mass than can be accounted for by the visible galaxies.
What effect is thought to be due to the presence of dark matter around spiral galaxies?
The rotation rates of spiral galaxies and orbital interactions among galaxies within clusters suggest the presence of extra mass around them.
What is the best description of the distribution of the galaxies that lie within about 200 Mpc of Earth?
The galaxies appear to be arranged in a network of filaments, or strings, surrounding large, empty regions of space known as voids.
What is the explanation of the low-redshift absorption lines in the spectra of quasars?
Intervening gas much closer than the quasar
What is the estimated percentage of dark matter in the universe?
90 percent
How did large galaxies form?
From the collisions and mergers of smaller galaxies
Galaxies sometimes interact at a distance, becoming distorted or changing shapes. Typically, how long does such an encounter take?
Several hundred million years
In the history of the universe, when was the shortest peak wavelength apparent?
500,000 years after the big bang and longest peak wavelength is present today. this is because individual photons stretch to longer (redder) wavelengths as the universe expands
what happens to galaxies as the universe expands?
galaxies stay roughtly the same size. Average distance increases with time both between galaxies in the universe. An observer in any galaxy sees more distant galaxies as moving away faster
cExamples of baryonic matter (contains protons and neutrons)
Matter in our bodies, dark matter consisting of Jupiter-size objects in galactic halos, matter in stars, matter in brown dwarfs.
Examples of nonbaryonic matter
Dark matter consisting of weakly interacting subatomic particles, matter that probably makes up the majority of dark matter
Two main candidates for making up majority of dark matter
WIMPS (nonbaryonic matter), and MACHOS (baryonic matter)(Massive compact halo objects.
What happened within the first 5 minutes of the Big bang?
Temperature fell to 10^15K, inflation occured, antielectrons (positrons) as common as electrons, strong force and electrowewak force first became distinct
What happened something after the first 5 minutes of the Big Bang?
galaxies formed, carbon nuclei formed by fusion, stars formed, photons of cosmic microwave background released
During the history of the universe, what important event occurred about 0.001 seconds after the Big Bang?
Most matter in the early universe was annihilated by antimatter.
Which of the following important events occurred earliest in the history of the universe?
Spacetime rapidly expanded during a brief period of inflation.
During the history of the universe, what important event occurred about 380,000 years after the Big Bang?
Light began to travel freely through the universe.
Essentially all the hydrogen nuclei that will ever exist in our universe was created __________.
by the time the universe was about 3 minutes old
Compared to when the cosmic microwave background was first released, the radiation of the cosmic microwave background today is __________.
fainter and has most of its photons at longer wavelengths
Grand unified theory
Predicts that the strong, weak, and electromagnetic forces should become indistinguishable at high temperatures
The ______ is a single force that unifies the electromagnetic weak forces
Electroweak force
A dramatic expansion of the universe thought to have occurred when the universe was only a tiny fraction of a second old
____ forces us to think about why the sky is dark at night
Olber's paradox
Observations of the _______ provide a way to test our theory of the Big Bang
Cosmic microwave background
When a particle of ordinary matter meets its precise opposite particle of antimatter, the result is _______ with complete conversion of mass into energy
Put these in order of when they occurred through the history of the universe from earliest to most recent
Particulate, galactic, stellar, planetary, chemical, biological, cultural
What are some cosmic signs (as opposed to possibly extraterrestrial)?
Constant, unchanging signal, identical repetitive pulses, random radio fluctuations, single strong visible light burst that fades away over months.
What may possible by extraterrestrial signals?
Sequence of pulses varying over time
What would an extraterrestrial observer outside our galaxy see when viewing Earth?
A pulsating radio signal that varies in intensity during each cycle.
Spectral evidence that nitrogen and oxygen are the most abundant gases.
Natural emissions minimized in the 18-cm to 21-cm wavelength called the "water hole"
As the mass of the central star increases, the distance to the habitable zone __________ and the size (width) of the habitable zone __________.
increases / increases
Suppose that our Sun was cool enough to include Mercury in its habitable zone. Which of the following would be true in that case?
Only Mercury would be in the Sun's habitable zone.
Scientists think it is very unlikely that complex and large forms of life could evolve on planets that orbit stars that are much more massive than the Sun. Why?
The expected lifetime of a massive star is too short to allow for the evolution of complex life
What is the average rate of star formation in our Galaxy?
10 stars every year
What is the "stellar habitable zone"?
The range of distances from a star in which an Earth-like planet could sustain liquid water.
Do astronomers expect to find planets around binary stars that are stable enough for life to develop? Why?
No. Planets may form stable orbits in binary systems, but the conditions on them won't be conducive to developing life.
Why do astronomers consider very long-wavelength, low-frequency radio waves not to be a good range to search for an extraterrestrial signal?
There are too many natural galactic sources that cause noise at these wavelengths.
Robot probes sent to the other planets of the solar system have demonstrated that life as we know it exists on which of the following?
Only on Earth
The Viking lander experiments that chemically searched for life on Mars could not have detected which of the following?
The most likely region of the radio spectrum for communication with other civilizations is in the "water hole." What part of the spectrum is this?
Between the radio emissions of hydrogen and OH
In what sense are viruses on the border between material that we consider living and that we consider nonliving?
Viruses cannot reproduce on their own but must make use of the genetic machinery of the cells they invade to multiply.
According to available physical and biological evidence, when did multicellular organisms first appear on Earth?
About 1 billion years ago
What is chemical evolution?
The evolution of biologically important chemicals from nonbiological chemicals
What were the first biologically important molecules produced in the Miller-Urey experiments?
Amino acids
What environmental factor works against Mars having any life on its surface?
Lack of a magnetic field
What is the most important piece of evidence known about Mars that suggests it once had an environment that could be supportive of life?
Dry river and lake beds
What question does the Drake equation attempt to answer?
What is the number of technological civilizations in the Galaxy?
What is the meaning of the term extremophiles?
Life-forms that have adapted to live in extreme environments