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Final Exam
N/A
134
Astronomy
Undergraduate 2
12/14/2011

Additional Astronomy Flashcards

 


 

Cards

Term
Astronomers use different types of telescope designs to observe light from different portions of the electromagnetic spectrum because...
Definition
light at different wavelengths interacts differently with matter, so we have to use different materials and methods for collecting short and long wavelengths. 
Term
We can see through a glass window because it
Definition
Transmits light
Term
Without telescopes or other aids, we an look up and see the Moon in the night sky because
Definition
It reflects visible light
Term
How does increasing the wavelength affect the energy and speed of a photon (a particle of light)?
Definition
Longer wavelength means lower energy, but the speed is unaffected.
Term
If you wanted to learn about an object's chemical composition, what would be the most useful?
Definition
The object's absorption line spectrum
Term
A dense object gives off...
Definition
A continuous spectrum
Term
A hot, low-density cloud of gas gives off...
Definition
An emission spectrum
Term
What is temperature a measure of?
Definition
The average kinteic energy of a group of particles.
Term
When a person falls off the edge of a cliff, the reason they fall is because...
Definition
the gravitational force of the Earth on the person is equal and opposite to the person's force on the Earth. The person's mass is so much smaller than the Earth's, they end up with a large acceleration while the Earth's acceleration is too small to be noticed
Term
If you are standing in Kalamazoo, which is 40o N latitude, where in your sky could you see Polaris, the North star?
Definition
Due North at an altitude of 40o above the horizon
Term
What is meant by a constellation?
Definition
A region of the sky with well defined borders
Term
The star Rigel is about 770 light years away from Earth. If Rigel were to explode in a supernova today, when could we know about it?
Definition
In 770 years.
Term
Using the Cosmic calendar, where the entire age of the universe is compressed into one year, roughly when did dinosaursgo extinct?
Definition
yesterday
Term
Roughly how many galazies are there in the obsevable universe?
Definition
100 billion
Term
A light year is approximately...
Definition
1013 km
Term

Which is the largest?

-a light year

-diameter of a typical galaxy

-distance to Pluto

-distance to the nearest star

-diameter of the sun

Definition
diameter of a typical galaxy
Term
Using the Cosmic Calendar, where the entire age of the universe is compressed into one year, when did our galaxy form?
Definition
in February
Term
Resolving power is the ability to...
Definition
reveal fine detail in an image
Term
Why do we put telescopes in space?
Definition
to reduce the effects of light pollution, to eliminate turbulence from the atmosphere, to avoid absorption of certain portions of the light spectrum by the atmosphere
Term
If you want to improve the angular resolution of a telescope, the best way to do so is to...
Definition
increase the diameter of the opening of telescope
Term
From lowest energy to highest energy, what is the correct order of electromagnetic radiation?
Definition
radio, infrared, visible light, ultraviolet, X rays, gamma rays
Term
as a planet in an elliptical orbit around the sun gets closer to the sun it goes...
Definition
faster because it gains kinetic energy as it loses gravitational potential energy
Term
when an ice skater is spinning and pulls in her arms, she spins:
Definition
faster because of conservation of angular momentum
Term
as a planet in an elliptical orbit around the sun gets gloser to the sun it goes...
Definition
faster because it gains kinetic energy as it loses gravitational potential energy
Term
What are the hallmarks of science?
Definition

-explanations must be based solely on natural causes and can not rely on divine intervention

-given two competing tested models that explain a natural phenomena, the simplest explanation is preferable

-a scientific model must make testable predictions which would force us to abandon or revise the theory if they are proved to be wrong

Term
What is a circumpolar star?
Definition
a star that is always above your horizon
Term
when you are standing in Kalamazoo, what is the point that is directly over your head?
Definition
the zenith
Term

The celestial sphere is another name for our universe.

True or False?

Definition
False
Term
Using the Greek naming system, what would you call the second brightest star in the constellation Orion?
Definition
Orionis-beta
Term
Why do stars look like they rise in the east and set in the west?
Definition
Because the Earth is rotating on its axis
Term
What is the ecliptic?
Definition
the plane of the Earth's orbit around the Sun
Term
What makes the North Star, Polaris, special in our night sky?
Definition
It does not move much during a night since it is very close to the North Celestial Pole.
Term
Elements heavier than H and He that we find on Earth, for example Silicon and Calcium, were...
Definition
created by nuclear fusion in the cores of an earlier generation of stars
Term
What was the first evidence astronomers discovered that led to the Big Bang Theory?
Definition
All galaxies outside the Local Group are moving away from us, and the farther away they are, the faster they're going
Term
How big is the Milky Way Galaxy?
Definition
It is roughly 100,000 light years in diameter and contains about 100 billion stars
Term
How old is the universe?
Definition
14 billion years old
Term
If the Earth were the size of a basketball, the moon would be roughly the size of...
Definition
a baseball 30 ft away
Term
How far is it to the nearest star, other than our Sun?
Definition
4 light years
Term
The average distance from the Earth to the Sun is...
Definition
1 astronomical unit (AU)
Term
When we say a spectrum is red shifted, it means the object
Definition
is moving away from us.
Term
If the temperature of a star increases from 2,000 K to 8,000 K the power it radiates
Definition
increases a factor of 256
Term
How would you describe the law of conservation of energy?
Definition
the total quantity of energy in the universe never changes
Term
If the distance between two planets is decreased by a factor of 4, the gravitational force between them....
Definition
increases a factor of 16
Term
What is a theory?
Definition
An explanation for a wide variety of observations that has been repeatedly tested, has a wide body of evidence that supports it, and has not failed any crucial test.
Term
The force of gravity is an inverse square law. What does this mean?
Definition
 If you triple the distance between two large masses, the gravitational force between them decreases by a factor of 9.
Term
How many degrees are in a full circle?
Definition
360
Term
What do we mean by "observable universe"?
Definition
Refers to the portion of the universe that we can see in principle, given the current age of the universe.
Term
What happens when the gravity of a massive star is able to overcome neutron degeneracy pressure?
Definition
The core contracts and becomes a black hole
Term

For a white dwarf to become a nova, it is necessary for it to have a companion star.

True or False?

Definition
True
Term
How do we know that pulsars are neutron stars?
Definition
No massive object, other than a neutron star, could spin as fast as we observe pulsars spin.
Term
You are more likely to survive passing through the event horizon of a very massive black hole than a less massive black hole.
Definition
True.
Term
What determines how strong the tidal forces on an object are?
Definition
The differences in how strong the gravitational force is on the nearest and fartherst parts.
Term
What evidence shows that black holes exist?
Definition
In binary systems that show a star with an invisible massive companion; in the cores of galaxies based on the motion of stars near the core.
Term
What explains why neutron stars spin rapidly?
Definition
Because conservation of angular momentum means the rate of spin will increase as a star collapses to form a neutron star.
Term
What determines how strong the tidal forces on an object are?
Definition
the differences in how strong the graviational force is on the nearest and farthest parts.
Term
Why do heavier elements require higher temperatures to fuse?
Definition
they have more positively charged protons in their nuclei, so have to be moving faster to approach close enough for the nuclear strong force to fuse them.
Term
What would you see if you were to observe astronaut Susan's fall into a relatively low mass black hole?
Definition

-Susan's clock would start to run slower than yours

-the light from her spaceship would become red shifted

-she would be ripped about by tidal forces as she approaches the event horizon

Term
Why is there an upper limit to the mass of the white dwarf?
Definition
the more massive the white dwarf, the greater the degeneracy pressure and the faster the speeds of its electrons. Near 1.4 solar masses, the speeds of the electrons approach the speed of light, so more mass cannot be added without breaking the degeneracy pressure.
Term

If the Sun were magically replaced by a one solar mass black hole, we would still continue to orbit in a period of one year.

True or False?

Definition
True
Term

In a white dwarf, we have packed the mass of the Sun into the volume of Earth.

True or False?

Definition
True
Term

When a brown dwarf cools, the degeneracy pressure drops and the brown dwarf gets smaller.

True or False?

Definition
False
Term

When does a massive star reach the point when it is about to go super nova?

 

Definition
When  the mass of its iron core reaches the point where electron degeneracy pressure can no longer sustain it.
Term
Why are star clusters ideal "laboratories" for stellar evolution?
Definition
Their stars all formed at about the same time and are roughly the same distance from Earth.
Term

The temperature needed to sustain H He fusion is approximately 10 million K.

True or False?

Definition
True
Term
How do we know what goes on under the surface of the Sun?
Definition
By a combination of helioseismology, neutrino detection, and mathematical models.
Term
In which portion of the sun is energy transported outward primarily through light in the visible range?
Definition
Photosphere
Term

The most common element in the Sun is hydrogen.

True or False?

Definition
True
Term

The mass of a neutrino is 30% of the mass of an electron.

True or False?

Definition
False
Term
As the sun spends more time on the main sequence, how do you expect its chemical composition to change?
Definition
It should have a higher concentration of iron Fe
Term
In a nuclear reaction, where does the energy come from?
Definition
A small amount of mass is turned into energy
Term
Given two identical stars A and B, if Star A is closer to us than Star B, how do their parallax angles compare?
Definition
Star A's parallax angle is larger than that of Star B.
Term

Open and globular clusters each typically contain a few hundred stars.

True or False?

Definition
False
Term
What is the spectral sequence in order of decreasing temperature?
Definition
OBAFGKM
Term
How long does it take energy generated in the core of the sun to escape into space?
Definition
Hundreds of thousands of years
Term
Our Sun is classified as...
Definition
a main sequence star
Term
Why are high pressures required to sustain nuclear reactions?
Definition
Because they increase the number of atoms in the core, making collisions between the nuclei occur more often
Term
What would happen inside the Sun if a slight rise in core temperature led to a rapid rise in fusion energy?
Definition
It would cause the core to expand and thereby cool.
Term
How old is our Sun?
Definition
5 billion years.
Term

An O star has the longest life as a main-sequence star.

True or False?

 

Definition
True
Term

M is one of the spectral types that is the coldest.

True or False?

Definition
True
Term
Cluster ages can be determined from...
Definition
main sequence turnoff
Term
How do we determine the mass of distant stars?
Definition
From their period and orbital speed in binary star systems.
Term
The temperature of Star A is twice the temperature of Star B, but its radius is only half as big as Star B's. Which star is more luminous?
Definition
Star A
Term
How would you correctly describe the stages of life for a low-mass star?
Definition
protostar, main-sequence, red giant, white dwarf
Term
If we do a survey of all the starswe can observe with the Hubble Space telescope, what would we find?
Definition
A greater number of red stars than blue stars.
Term
When does a star turn into red giant?
Definition
After it uses up all of the H in the core.
Term
Why do protostars glow?
Definition
Because they have heat from the gravitational contraction of the cloud.
Term
What do we mean when we refer to "stellar temperature"?
Definition
The surface (photoshere)
Term
When a star becomes a red giant, why does it become much brighter?
Definition
because it is getting larger.
Term
You measure that Procyon has a stellar parallax of 0.05 arcseconds. How far away is Procyon?
Definition
20 parsecs, or 65.2 light years.
Term
What is a WIMP?
Definition
A massive particle that only interacts via the weak force and gravity.
Term
What might be causing the expansion of the universe to accelerate?
Definition
dark energy
Term
What evidence do we have that dark matter exists?
Definition

-orbital speedsin galaxies is too high to be held in place by the gravity from the luminous matter

-the speeds of galaxies in galactic clusters is too high to account for by the gravity from the luminous matter

-the temperature of hot gas in galactic clusters is too high to be bound by the gravity from luminous matter

-gravitational lensing

Term
Why do we expect that WIMPs should be distributed throughout galactic halos, rather than settled into a disk?
Definition
Since they do not interact via the electromagnetic force, they could not emit radiation to settle into the disk like ordinary matter could.
Term

When we say that a cluster of galaxies is acting as a gravitational lens, what do we mean?

 

Definition
It bends or distorts the light coming from galaxies located behind it.
Term
What do we mean by MACHOs?
Definition
Particles with mass that have condensed into a compact form and are found in the halo of the galaxy
Term
What are the two key observational facts that led to widespread acceptance of the Big Bang model?
Definition
the cosmic background radiation and the helium content of the universe
Term
How far back can we see light from after the Big Bang and why?
Definition
380,000 years after the Big Bang, because that is when electrons became bound to the nuclei and photons were free to travel without scattering.
Term
What are the largest scale structures in the universe?
Definition
chains, sheets, and walls of galaxies that surround voids
Term
Why isn't space expanding within systems such as our solar system or the Milky Way?
Definition
Their gravity is strong enough to hold them together against the expansion of the universe.
Term
What kinds of objects lie in the halo of the Milky Way galaxy?
Definition
globular clusters
Term
When we plot the velocity of stellar orbits as a function of distance from the center of the Milky Way galaxy, what do we find?
Definition
As we go farther out, the velocity remains relatively flat.
Term
Stars in the halo of the Milky Way Galaxy tend to be..
Definition

-in globular clusters

-red and yellow

-older

-poor in heavy elements

Term
What evidence supports the existence of a black hole at the center of our galaxy?
Definition
The motions of the gas and stars at the center indicate that it contains 4 million solar masses within a region only 3 light-years across
Term
Where in our galaxy are we most likely to find stars that have Earth-like planets?
Definition
the disk
Term
Of the various types of gas found between the stars, within which type do stars form?
Definition
T=10 K, molecular clouds, density=104 particles/cm3
Term
Which are the regions of most active star formation in the milky way galaxy?
Definition
in the spiral arms
Term
what do we observe in a region of space that indicates that star formatin is occuring?
Definition
High mass blue stars and inonization nebula
Term
Which model of the universe gives the oldest age for its present size?
Definition
an accelerating universe
Term
Helium originates from what?
Definition
mostly from the Big Bang with a small contribution from stella nucleosynthesis.
Term
If astronomers had discovered that the cosmic microwavebackground was precisely the same everywhere, instead of having very slight variations in temperature, then we would have no way to account for...
Definition
how galaxies came to exist
Term
In stars, helium can sometimes be fused into carbon and heavier elements. Why didn't the same fusion processes produce carbon and heavier elements in the early universe?
Definition
By the time stable helium nuclei had formed, the temperature and density had already dropped too low for helium fusion to occur.
Term

The cosmic background radiation is expected to contain redshifted emission lines from hydrogen and helium, and it does.

True or False?

Definition
False
Term
Which of the four fundamental forces is the weakest?
Definition
gravity
Term
What would be the most appropriate method to determine the distance of stars that are about 10 light years away?
Definition
Parallax
Term
What evidence do we have for a super massive black hole at the center of our Milky Way Galaxy?
Definition
The stars near the center are orbiting with such high speeds that indicate an object of roughly 3 million solar masses which is less than one light year across.
Term
Which of the following make good standard candle and why?
Definition
White dwarf supernova, because white dwarfs all have a critical mass of 1.4 Msolar
Term
What would be the most appropriate method to determine the distance of stars in nearby galaxies?
Definition
Cepheids
Term
how does the interstellar medium obscure our view of most of the galaxy?
Definition
It absorbs or scatters visible, ultraviolet, and some infrared light.
Term
What portion of the spectrum would reveal where cosmic rays from supernova explosions collide with atomic nuclei in gas clouds?
Definition
gamma
Term
What role do galaxies play in making life (as we know it on Earth) possible?
Definition
they allow the heavy element enriched gas from dying stars to be recycled in new star systems
Term
An isolated proto-galactic cloud with large net angular momentum is likely to form as which basic type of galaxy?
Definition
Spiral
Term
In the "tuning fork" diagram of Hubble's classification of galaxies, which corresponds to the most spherical in shape?
Definition
E0
Term
How does the estimated age of the universe depend on Hubble's constant?
Definition
the larger H0, the younger of the universe
Term

If Hubble's constant is Ho = 22 km/s/million light years and you measure the redshift of a galaxy and determine it's velocity is 550 km/s, what distance was the galaxy at?

 

Definition
25 million light years
Term
How lumionous is a Cephid with a period of 30 days?
Definition
10,000 L
Term
In the "tuning fork" diagram of Hubble's classification of galaxies, which corresponds to a barred spiral?
Definition
SBc
Term
A very dense proto-galactic cloud is most likely to end up as...
Definition
an elliptical galaxy, because it would form stars before the matter had time to settle into a disk.
Term

Comared to spiral galaxies, elliptical galaxies are redder and rounder.

True or False?

Definition
True
Term
What would be the most appropriate method to determine the distance to the most distant observable galaxies?
Definition
Hubble's Law
Term

Of the critical density of the universe, roughly 4% is ordinary matter, 25% is dark matter, and 71% is dark energy.

True or False?

Definition
True
Term
What do we mean by the critical density of the universe assuming no dark energy were present?
Definition
The average density the universe would need in order for gravity to balance out the expansion
Term
Although the most astronomers assume dark matter really exists, there is at least one other possible explanation for the phenomena attributed to dark. What is it?
Definition
There could be something wrong or incomplete with our understanding of how gravity operates on galaxy-size scales.
Term
Why do we call dark matter "dark"?
Definition
It emits no or very little radiation of any wavelength
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