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AST1002 Final Review
old exam questions
91
Astronomy
04/25/2011

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Term
How many high tides are there in a day on average?
Definition
2
Term
Why do we see both total and annular solar eclipses?
Definition
the moon's orbit around earth is not exactly circular
Term
of these stars, which is coolest: red, yellow, green, dark red
Definition
dark red
Term
When we think of epicycles, we think of:
Definition
Ptolemy
Term
What would you use to image very cold clouds containing atomic hydrogen?
Definition
radio telescope
Term
What is the most important parameter that determines the behavior of star?
Definition
mass
Term
Which planet is least dense?
Definition
Saturn
Term
Which planet has the largest magnetic field?
Definition
Jupiter
Term
What objects can be binary?
Definition
main sequence stars, black holes, neutron stars, red giants, and white dwarfs
Term
Increasing the diameter of a telescope primary lens:
Definition
makes light gathering power go up
Term
Black body radiation is
Definition
that any object at any temperature above absolute zero will emit a characteristic distribution of wave lengths of light
Term
What balances the sun's huge gravitational force, keeping it from collapsing?
Definition
radiation pressure
Term
What is the last and heaviest element that can be created from fusion in the normal evolution of a high-mass star?
Definition
Iron
Term
As our Sun leaves the main sequence:
Definition
It will have a helium flash and move into the horizontal branch of the H-R diagram
Term
If you were to see signals coming into your radio telescope receiver, you'd think you were seeing
Definition
signals from a rapidly spinning neutron star
Term
An old star cluster in the Halo of the milky way is generally a
Definition
globular cluster
Term
A new, star-like object appears to have magnitude -10 M. It could be:
Definition
a supernova in the Milky Way or some distant galaxy
Term
Elusive particles created by the sun that allow astronomers to determine what nuclear fusion reaction powers it
Definition
Neutrinos
Term
How massive can a black hole be?
Definition
Any size, as long as all the mass is within the Schwarzschild radius for that mass value
Term
Noting the turnoff mass in a star cluster on an H-R diagram allows you to determine its
Definition
age
Term
What kind of stars are used as "standard candles" to estimate the distances to star clusters in the Milky Way?
Definition
Cepheid and RR Lryae Variables
Term
The milky way is a
Definition
spiral galaxy
Term
What is SGR A*
Definition
the location of a super massive black hole at the center of the Milky Way
Term
What represents the Local Group?
Definition
Andromeda, Sagittarius drawf, large and small magellanic clouds, milky way, and other neighbors
Term
What is a proposed explanation for gamma ray bursters?
Definition
a hypernova making black holes and bi-polar jets
Term
*What are typical values of luminosity in AGNs?
Definition
Greater than 10^37 W, which means they consumer on average on sun's mass every couple of years.
Term
*What is special about the emission spectra coming from AGNs?
Definition
they have non-stellar emissions
Term
*what is special about the energy output of an AGN?
Definition
it is highly variable, indicating that the emission source is very compact (> a parsec in size)
Term
*what do AGNs look like?
Definition
usually have jets and accretion disks, with a black hole at the center
Term
*What to AGN emission lines look like?
Definition
Very broad, indicating that their source is undergoing rapid internal motion (in more than one direction)
Term
What do data points near region A refer to?
Definition
older galaxies near to to us
Term
What do data points near region C refer to?
Definition
younger galaxies that are far from us
Term
Fact that the data falls below the straight lines near region C means that
Definition
the early universe was expanding more slowly than it is now
Term
What is the shape of an open universe?
Definition
the potato chip/saddle shape
Term
If two laser pointers sent out two parallel beams into space, they would ultimately cross at
Definition
a closed universe
Term
The universe is similar in both ways from us, 14 billion years each way. Why is this? They could not have communicated because it would have taken 28 billion years and that is older than the universe itself.
Definition
Inflation theory can explain it
Term
What makes up critical density?
Definition
visible matter, dark matter, dark energy
Term
What information does the cosmic background radiation give us?
Definition
a picture of the sizes of early dark matter-shrouded galaxies, and a measure of the temperature of the present universe (2.7 K)
Term
How far does light travel in 32.6 years?
Definition
10 parsecs
Term
tripling the diameter of a telescope with angular resolution of 1 arcsecond makes the angular resolution:
Definition
1/3 of an arcsecond
Term
Find mass of a black hole given we see a star orbit it once a year, at a distance of 10 AU (keppler's law: M=A^3/P^2
Definition
1000 thousand solar masses
Term
a star has a parallax of .001 arcseconds. how far away is it?
Definition
1000 parsecs
Term
two same size stars, one is 4x hotter. How much more luminous is it?
Definition
256 times
Term
How long is a year on Pluto? (40 AU from sun)
Definition
253 years
Term
a star blows up, releasing 1.8x10^47 J of energy. It is what kind of star?
Definition
solar mass star
Term
In the milky way, the sun is located:
Definition
about 8kpc from the center
Term
stars in the outermost regions of the milky way
Definition
orbit faster than expected based on the galactic mass we can see
Term
Most of the mass of the milky way exists in the form of
Definition
dark matter
Term
Hubble's law implies that
Definition
the greater the distance to a galaxy, faster it is moving away from us
Term
If the light from a galaxy fluctuates in brightness very rapidly, the region producing the radiation must be
Definition
very compact
Term
Quasar spectra are
Definition
strongly redshifted
Term
charged particles spiraling around magnetic field lines can produce
Definition
synchrotron radiation
Term
the Tully-Fisher method
Definition
Inferring the distance to the galaxy through a measurement of its rotation rate
Term
Galaxies that look like normal spiral galaxies, but have extremely bright galactic nuclei
Definition
Syfert galaxies
Term
More than ___% of the mass in the universe is dark
Definition
90
Term
A close encounter or collision between two galaxies may result in
Definition
a burst of star formation
Term
inflation theory solves the cosmological
Definition
horizon problem
Term
galactic distances used to measure acceleration of universe are determined by observations of
Definition
exploding white dwarfs
Term
chemical elements that form the basic molecules needed for life are found
Definition
commonly through the cosmos
Term
the centers of quasar are typically
Definition
AGN
Term
gravitational lensing causes
Definition
the light from distant stars to be bent or focused by unseen massive objects in its path
Term
signature of a pulsar?
Definition
periodic blips in the received radio signals usually occuring at short intervals
Term
takes 8.3 minutes for light to reach earth. new object is found, 100 AU from sun. how long does it take light to reach this object?
Definition
833 minutes
Term
How long does it take the moon to orbit on its axis?
Definition
28 days
Term
how long does it take the sun to rotate once on its axis?
Definition
about one month
Term
most important parameter that determines a star's evolution?
Definition
it's mass
Term
astronomers generally believe that planetary magnetic fields originate from:
Definition
the dynamo effect and liquid, metallic cores
Term
millisecond pulsars are mostly observed in
Definition
globular clusters
Term
biggest magnetic fields in the universe are probably associated with:
Definition
neutron stars and magnetars
Term
if you observe 4 identical images of the same quasar,
Definition
there is probably a dark matter between you at the quasar
Term
If you observe an object orbiting another object, you can determine:
Definition
the total mass of the binary system
Term
what constellation was rising in the east at the beginning of the semester, and is now setting in the west at the end of the semester?
Definition
orion
Term
if the moon's orbit were a little larger, solar eclipses would be
Definition
more likely to be annular
Term
Light coming from star has wavelength of 1000 nm. How hot is it?
Definition
2900 K
Term
Wavelength in nanometers of light coming from very hot star (about 29,000 K)
Definition
100 nm
Term
Comet orbits the sun once every 10 years. What is the average distance from the sun to the comet?
Definition
4.64 AU
Term
Temperature of star is 59,000 K. How much more power does it emit than the sun? (Sun is 5900 K)
Definition
10,000 times more
Term
why doesn't Venus have a magnetic field?
Definition
its extremely slow rotation doesn't produce a significant dynamo effect.
Term
Sun's average density is almost exactly the same as:
Definition
Jupiter
Term
Star has parallax of .05 arcseconds, its distance is
Definition
200 parsecs
Term
in the proton-proton cycle, lost mass is:
Definition
converted to energy
Term
when multiple radio telescopes are used for interferometry, resolving power (angular resolution) is most improved by increasing:
Definition
distance between telescopes
Term
emission nebulae like M-42 occur only near stars that emit large amounts of
Definition
ultraviolet radiation
Term
on a H-R diagram, a protostar would be
Definition
above and to the right of the main sequence
Term
characteristics of globular clusters
Definition
old age, hundred of thousands of stars, only about 30 ly wide
Term
a recurrent nova could eventually build up to:
Definition
a type I supernova
Term
What is Cygnus X-1
Definition
leading candidate for an observable black hole binary system
Term
Mass range for a neutron star
Definition
1.4 to 3 solar masses
Term
Logical sequence of galaxy evolution:
Definition
quasar, active galaxy, and normal galaxy
Term
Obler's paradox is resolved by
Definition
the finite age of the universe
Term
horizon problem in standard big bang model is solved by having the universe:
Definition
inflate rapidly early in its existence