234 terms

Ast 1002 Final

Hw 1-12
How long does it take light to travel a distance of one light year?
One year or about pi x 107 seconds.
• What is the unit that we use to measure distances in the solar system?
The astronomical unit or AU is very convenient.
• If Earth rotated on its axis twice as fast as it currently does, but its motion around the Sun stayed the same, then
the night would be half as long
• A long thin cloud that stretched from directly overhead to the western horizon would have an angular size of
90 degrees
6. In December we would see the Sun in the direction of the constellation(s)...
Sagittarius and Capricorn
If the Moon's orbit around Earth were a little larger, solar eclipses would be
more likely to be annular
What two pieces of information are needed to determine the diameter of a far away object?
Distance and angular size
The seasons are caused by the precession of the Earth's
The solar day is longer than the sidereal day
The most northern location on Earth where the Sun can be seen directly overhead at noon is called
The Tropic of Cancer
What is the approximate position of Polaris on the Celestial Sphere?
Approximately RA = 2h 30 min, Dec = 89 degrees
The Age of Aquarius refers to what?
It means that in the future the vernal equinox will occur in a direction in line with the constellation Aquarius due to the precession of the Earth's axis of rotation.
5. When a thin crescent of the Moon is visible just before sunrise, the Moon is in its
waning phase
you put an apple 10 m away from your eye in line with the moon, what do you predict?
It would "eclipse" the moon.
• The alpha star in a constellation is (as seen from Earth):
The brightest star in a constellation as seen from Earth.
• A major flaw in Copernicus's model was that it still had
Circular Orbits
• An asteroid with an orbit lying entirely inside Earth's orbit
has an orbital semimajor axis of less than 1 AU
• Galileo's observations of Venus demonstrated that Venus must be
Orbiting the Sun
• showing the motion of a ball near Earth's surface, depicts how gravity
Causes the ball to accelerate downwards
• How long would a radar signal take to complete a round trip between Earth and Mars when the two planets are 0.7 AU apart?
about 11.6 minutes
• The light coming from a star has a dominant wavelength of 1000 nm. How hot is the star in degrees Kelvin?
• What is the dominant wavelength in nanometers of the light coming from a very hot star (about 29,000 K)?
• The H-alpha spectral line 656 nm coming from a distant star appears at a wavelength of 100 nm in the spectrometer. What can we say about the star?
It is moving towards us at 85% the velocity of light
• Comet X orbits the Sun every 10 years. What is the average distance (semi major axis) of the comet from the sun?
4.64 AU
• The temperature of a distant star is determined to be 59,000 K. How much more power does it emit than the sun does?
10,000 times more
• The main advantage to using the Hubble Space Telescope it that focusing problems due to atmospheric disturbances are eliminated
• The term "seeing" is used to describe how bright an object the human eye can tolerate without damage to the retina.
• A CCD is used to electronically record images from a telescope
• Radio telescopes are large in part to improve their angular resolution, which is poor because of the long wavelengths at which they
• Infrared astronomy can only be done from space
• X-ray and gamma-ray telescopes employ the same basic design as optical instruments
• Because gamma rays have very short wavelengths, gamma-ray telescopes can achieve extremely high angular resolution
• The main reason that most professional research telescopes are reflectors is that
mirrors produce sharper images than lenses do since there is no chromatic aberration.their images are inverted
• If telescope mirrors were made in odd sizes, the one with the most light-gathering power (even if the mirror is not circular) would be
a rectangle with two 1-m sides and two 2-m sides.
The PRIMARY reason professional observatories are built on the highest mountain tops is to
Reduce atmospheric blurring
When multiple radio telescopes are used for interferometry, resolving power (angular resolution) is most improved by increasing
the distance between telescopes
The Spitzer Space Telescope is stationed far from Earth because
This infrared telescope actually does not orbit the Earth, but follows our planet around the Sun, reducing the heat interference from Earth
The best way to study young stars hidden behind interstellar dust clouds would be to use
Infrared light
(Resolution) is sharpest when the ratio of wavelength to telescope size (i.e. lambda/D)
is small
the best frequency range in which to study the hot (million-kelvin) gas found among the galaxies in the Virgo cluster would be
in x-rays
An FSU student is observing the phases of Venus with his 8 inch reflector telescope, and a UF student is doing the same with a 16 inch reflector telescope. How much more light gathering power does the UF telescope have?
4 times more
Again, an FSU student is observing the phases of Venus with his 8 inch reflector telescope, and a UF student is doing the same with a 16 inch reflector telescope. How much "more" resolving power (i.e. angular resolution) does the UF telescope have?
Twice as much.
Once again: The FSU student and the UF student decide to do some radio astronomy and look at an intergalactic molecular cloud with their 30 meter dishes. They are looking at 60 micrometer light. What is the resolving power of each of these telescopes.
.5 arcseconds
The FSU student and the UF student decide to do some radio astronomy and look at an intergalactic molecular cloud with their 30 meter dishes. They are looking at 60 micrometer light. The decide that the resolution is not sufficient to see the details of the cloud. What can they do?
They each stay at home, but get a fast internet link, and link the outputs of the two radio telescopes together with a computer.
If you wanted to detect gamma ray radiation from a very violent stellar event, what would you do?
Write a proposal to NASA to get observation time on the Compton Telescope
All the terrestrial planets lie inside the asteroid belt
Pluto's orbit has the lowest inclination to the ecliptic of any planet.
One characteristic of the Terrestrial planets is their extensive moon systems.
All the planets' orbits are evenly spaced
Earth is nearly twice as large as Venus.
All the planets revolve around the Sun counter clockwise, except for Venus and Uranus.
All the planets orbit the Sun in exactly the same plane as the Earth
The two smallest planets, Mercury and Pluto, have no moons.(Assume Pluto is a planet!)
All four Jovian planets are thought to have cores larger than Earth.
All Jovian planets have rings around their equators and at least eight moons.
Pluto is more similar to the jovian planet's icy moons than to any of the other planets
Due to their great masses, all four Jovian worlds are much denser than the earth.
A Kuiper Belt object was recently discovered that may be larger than Pluto.
True (Eris)
Barringer Crater in Arizona is an example of a meteorite impact
Most astronomers now believe the demise of the dinosaurs 65 million years ago was caused by a large asteroid impacting the Yucatan peninsula area
Meteor showers are the result of collisions between asteroids.Meteor showers are the result of collisions between asteroids.
Carbonaceous asteroids contain fragile organic molecules
Many astronomers now regard Pluto as one of the thousands of Kuiper Belt bodies found beyond Neptune
Cometary dust tails lag behind the bluish ion tails as the comet rounds the Sun.
Most comets are believed to originate from the Oort Cloud
The Oort Cloud lies closer to the Sun than the Kuiper Belt
Researchers estimate that the total mass of the asteroid belt is about 1/10 that of the Moon's mass
Some meteorites are believed to have come from Mars and the Moon.
As a rotating gas cloud contracts, it spins faster
In the solar nebular theory, the dusty disk condensing around the Sun's equator became the ecliptic plane in which the planets then formed
In addition to revolving around the Sun counter clockwise, most planets also rotate on their axis counter clockwise.
Any successful model for the formation of the solar system must explain why the orbits of the planets have low eccentricities.
Astronomers have not yet been able to detect planets outside our solar system
We would expect other planets beyond our own solar system to orbit the equators of their home stars, as our own planets orbit the Sun.
In some cases, astronomers have detected extrasolar planets as they pass in front of their stars.
The magnetic field of the Earth probably arises from what process or condition?
A dynamo effect due to the motion of the electrically conducting molten iron core
Sunlight absorbed by the Earth's surface is re-emitted in the form of
Infrared Radiation
Planet X has a radius 10 times smaller than the Earth's radius, and a mass also 10 times smaller than Earth's mass. If you stand on Planet X, how much more or less would your weight be?
10 times more
The most likely theory for the formation of the moon is that it
formed from a sideways collision from a mars sized object
a plane traveling at 10 km is in the
Without the greenhouse effect operating in our atmosphere
Earth would have an average temperature of -23 degrees Celsius
Which of these gases is least abundant in our atmosphere
What is true of the Moon's orbital and rotational periods
they are equal
The Moon's near side always faces Earth due to
the earth's tidal force
What is true of spring tides?
The difference between low and high tides would be smallest
Which of these gets so bright as to be seen in daylight at times?
Which three worlds have almost identical densities
Mercury. Venus, and Earth
Which planet shows the widest range of surface temperatures between day and night?
How does Mercury's rotation rate relate to its orbit around the Sun?
Its rotation rate is 3/2 as long as its yer due to its tidal resonances
Venus' rotation
takes longer than its rotation around the sun
The atmospheric pressure on Venus
is 90 times higher than on Earth
What is the chief component of the Venusian atmosphere
Carbon dioxide
The chief gas in the martian atmosphere is
carbon dioxide
Why are Mars's seasons more extreme than those of the earth?
seas dried up long ago. axial tilt is slightly more than our 23.5 degrees. orbit is more eccentric than our almost circular one. weather is driven by evaporation from the polar ice in its summer.
Why doesn't Venus have a magnetic field?
its extremely low rotation doesn't produce a significant dynamo effect
In brightness (as seen from Earth), Jupiter is second only to the planet ________ most of the time.
In the telescope, ________ shows the most turbulent atmosphere with changes easily seen even with amateur telescopes.
The most famous and long lasting storm in the solar system is Jupiter's ________ spot
great red
Jupiter is largest and brightest in our skies when seen at
Adams and Leverrier predicted the position of ________, which Galle confirmed.
William Herschel discovered the green disk of ________ as the first telescopic planet.
While Saturn is almost as large as Jupiter, its mass is only about ________ of Jupiter's.
one third
The oblateness of the jovian disks is caused by their rapid ________.
Compared to the terrestrial planets, the Jovians have ________ average densities
Of the planets, ________ is the least dense, and could float on water
The oblateness of the Jovian disks refers to their ________ equatorial diameters, compared to the polar diameters.
Like Jupiter's, Saturn's rotation is fast and differential, with the ________ rotating fastest.
Unlike Jupiter and Saturn, at Uranus and Neptune the ________ rotates the slowest
In general, wind direction ________ between adjacent bands in Jupiter's atmosphere
Jupiter's bright zones are cloud streams made of ________ ice crystals
Jupiter's darker ________ are complex in color and origin, with complex organic molecules including carbon, sulfur, and nitrogen
The Great ________ Spot of Neptune was striking in 1989, but gone by 1995
Uranus and ________ are very similar in size, mass, and color.
The most abundant element (molecule) in Saturn's atmosphere is
________ looked very bland in Voyager 2 photos in 1986, but as equinox approached in the 1990s, its disk showed belts, zones, and storms
Because it has a higher percentage of ________, Neptune appears even bluer than Uranus
Compared to Jupiter, the element ________ is notably less common in Saturn's atmosphere, perhaps condensing to fall coreward as rain.
The mantles of Jupiter and Saturn are made of liquid metallic_________.
Jupiter emits twice the heat it gets from the Sun; the source of most of this energy is
gravitational contraption/ helium precipitation
While the rotation axis of _____________ is only tilted 29 degrees, its magnetic fields are just as strange as its twin's is.
Their magnetic fields should originate in the planets' ________, but those of Uranus and Neptune don't even come close.
Jupiterʹs magnetic field is produced in its rapidly spinning mantle of liquid
Metallic Hydrogen
What is thought to cause Io's volcanism?
tidal stresses from both Jupiter and Europa
The surface of Europa is most like the earth's
Arctic Ocean
The weak magnetic fields around Europa and Ganymede were found during flybys of
Of the Jovian satellites, which shows the oldest, most cratered surface
Which of these moons has the densest atmosphere?
For a moon the same density as its planet, the Roche limit lies at ________ times the radius of its planet
The Cassini Division is a gap in Saturn's rings caused by
Gravitational interaction with Mimas
What is the meaning of the solar constant?
the amount of energy that earth receives per unit area and unit time
The Sun's average density is almost exactly the same as
What two energy transport mechanisms, in order from outside the core to the surface, is found in the Sun?
radiative diffusion, convection
The solar winds blow outward from
Coronal holes
A loop of gas following the magnetic field lines between sunspots' poles is
As the Sun rotates, an individual sunspot can be tracked across its face. From eastern to western limb, this takes about
about two weeks
A maximum in solar activity should next occur about
What natural barrier must be overcome in order for two portons to collide and fuse together
electrostatic repulsion
In the proton-proton cycle, the helium atom and neutrino have less mass than the original hydrogen. What happens to the "lost" mass?
its is converted to energy E=MC^2
The solution to the solar neutrino problem which won a Nobel Prize in 2002 was
2/3 of the neutrinos decay into a new form in the 8 minutes to Earth
The speed of light is 3.00 × 10 m/s. If 2.00 kg of mass is converted to energy, how much energy will be produced?
1.80 × 10^17 J
A star has a parallax of .05 arc seconds, its distance is
20 parsecs
If spectroscopic luminosity classification gives us an estimated distance to the faint star SAO 47552 of about 3300 light years, then its parallax would be only
.001 arseconds
The stars α Cygni and β cygni are in the constellation Cygnus. Which statement can we claim is true?
α cygni appears brighter
Two stars both have parallaxes of 0.023", but star A has apparent magnitude +2.3, while star B is magnitude +7.3. Which statement is true?
Star A is both 100× brighter and more luminous than star B
The spectral type of a star is primarily a measure of its
Which of these stars would be the hottest?
What can be said with certainty about a red star and a blue star
The blue star is hotter than the red star
Which of these pairs of binaries would appear most similar in color telescopically
MIV and K9V
In general, what can be said about type O and B stars compared to type K and M stars
They are hotter and younger
The stars with masses comparable to our Sun's, but sizes like the earth are
White dwarfs
In the H-R diagram, what are the two most important (common) types of data plotted
spectral classes (temperature) and absolute magnitudes (luminosity)
On the H-R diagram, our Sun lies
at about the middle
On the H-R diagram, red supergiants like Betelguese lie
top right
Compared to the size of the Sun, stars of all types range from approximately
.01 to 1000 solar radii
Binary stars separated enough to be resolved in a telescope are called
visual binaries
If we know the average separation and period of revolution for a binary system, we can then determine
the total mass of the system
What information can be gained from the light curves of eclipsing binaries
their relative sizes and periods of orbit
Interstellar gas is composed mainly of
90%hydrogen and 9% helium
dark nebulae
can be penetrated only with longer wavelengths such as radio and infrared
Due to absorption of shorter wavelengths by interstellar dust clouds, distant stars behind the clouds appear
Emission nebulae like M-42 occur only near stars that emit large amounts of
Ultraviolet radiation
What is the primary visible color of an emission nebula
red due to ionized hydrogen atoms
What two things are needed to create an emission nebulae
hot stars and interstellar gas, preferably hydrogen
What information does 21 cm radiation provide about the gas clouds
their motion their distribution their density their temperature
The average temperature of the typical dark dust cloud is about
about 100 k
When an electron in H changes its spin from the same to the opposite direction as the proton, it
emits a radio wave photon
On a H-R diagram, a protostar would be
above and to the right of the main sequence
The single most important determinant of the temperature, density, radius, luminosity, and pace of evolution of a protostar is its
How long does it take an M class star to reach the main sequence, compared to a solar type star
about 20 times longer
Which is characteristic of globular star clusters?
old age and hundreds of thousands of stars lying about 300ly wide
Compared to a cluster containing type O and B stars, a cluster with only type F and cooler stars will be
In a fairly young star cluster, if the most massive stars are swelling up into giants, the least massive stars are
continuing to shine as main sequence stars
Noting the turnoff mass in a star cluster allows you to determine its
Which is used observationally to determine the age of a star cluster
the luminosity of the main sequence turn off point
What is the typical age for a globular cluster associated with our Milky Way?
10 to 12 billion years
The brightest stars in a young open cluster will be
massive blue stars at the top left of the hr diagram
A recurrent nova could eventually build up to a
type 1 supernova
What can you conclude about a Type I supernova?
it was originally a low mass star
Which of these does not depend on a close binary system to occur?
a type II supernova
The Chandrasekhar Limit is
the upper mass limit for a white dwarf
Type II supernovae occur when their cores start making
The heaviest nuclei of all are formed
in the core collapse which sets the stage for a type II supernova
Which of the following best describes the evolutionary track of the most massive stars on a H-R diagram?
horizontal right
As a 4 to 10 solar mass star leaves the main sequence on its way to becoming a red supergiant, its luminosity
remains roughly constant
A 20 solar mass star will stay on the main sequence for 10 million years, yet its iron core can exist for only a
In a neutron star, the core is
made of compressed neutrons in contact with each other
Important properties of young neutron stars are
extremely rapid rotation and a strong magnetic field
An object more massive than the Sun, but roughly the size of a city, is a
neutron star
The mass range for neutron stars is
1.4 to 3 solar masses
Most pulsars are observed only as ________ sources
Many of the millisecond pulsars lie in
globular clusters
X-ray bursters occur in binary systems, containing a
red giant and neutron star
A proposed explanation for gammaray bursters isA proposed explanation for gammaray bursters is
hypernova making black holes and bi-polar jets coalescence of a neutron star binary
In a hypernova, a very energetic supernova creates a
black hole
The densely packed neutrons of a neutron star cannot balance the inward pull of gravity if the total mass is
greater than Schwartzschild's limit of 3 solar masses
What explanation does general relativity provide for gravity?
gravity is the result of curved spacetime
As a spaceship's velocity gets closer to the speed of light
its length will decrease and its clock will run more slowly
As a spaceship nears an event horizon, a clock on the spaceship will be observed
to run slowly
If light from a distant star passes close to a massive body, the light beam will
bend towards the star due to gravity
What is Cygnus X-1?
the leading candidate for an observable black hole binary system
The largest known black holes
lie in the centers of the most massive galaxies
A method for identifying a black hole is to
look for their effects on nearby companions
In the Milky Way, the Sun is located
at about halfway out from the center
A telescope searching for young, bright stars would make the most discoveries if it were pointed
within a spiral arm
The first stars that formed the Milky Way now
have chaotic orbits
Stars in the outermost regions of the Milky way
orbit faster than astronomers would expect based on the galactic mass we can see
Most of the mass of the Milky Way exists in the form of
dark matter
a Cehpheid variable star with luminosity 1000 times that of the Sun has a pulsation period of roughly
4 days
What do we expect to find at the very center of our galaxy?
A super massive black hole called SGR A*
Gravitational lensing leads to what?
It causes the light from distant stars to be bent or focused by unseen massive objects in its path.
Using the method of standard candles, we could in principle estimate the distance to a campfire if we knew
The number of logs burning
Within 1 Mpc of the sun there are about
45 galaxies
Hubble's law implies that
the greater the distance to a galaxy the faster it is moving away fro us
If the light from a galaxy fluctuates in brightness very rapidly, the region producing the radiation must be
very small
Quasar spectra
are strongly redshifted
Active galaxies are very luminous because they
contain black holes in their core
active galaxies
emit large amounts of energy at all wavelengths
Charged particles spiraling around magnetic field lines produce
synchroton radiation
The Tully Fisher method involves
inferring the distance to a galaxy through a measurement of its rotation rate
A Syfert galaxies
look like normal galaxies, but have extremely bright galactic nuclei
The masses of nearby spiral galaxies can be determined by studying their
rotation curves
More than ________ percent of the mass in the universe is dark
More than ________ percent of the mass in the universe is dark
from a close encounter or collision between two galaxies
A logical sequence of galaxy evolution would be
quasar, active galaxy, normal galaxy
The Virgo Cluster, the Local Group, and some other local galaxy clusters form the
the local super cluster
Oblers's paradox is resolved by
finite age of the universe
The galactic distances used to measure the acceleration of the universe are determined by observations of
exploding white dwarfs
The horizon problem in the standard Big Bang model is solved by having the universe
inflate rapidly early in its existence
when the universe was 10 years old, the density of radiation was
much greater than that of matter
The chemical elements that form the basic molecules needed for life are found
commonly through the cosmos
The LEAST well known factor in the Drake Equation is
the average lifetime of a technology competent civilization
NASA's Space Shuttle travels at 17,500 mph. If it traveled to the next Sun-like star at that speed, the trip would take a time at least (if not more than)
100 millennia
A radio-wavelength emission observed by aliens that comes from our solar system with a 24 hour periodic signal shape would come from
human made signals on earth
habitable zone surrounding a main sequence K-type star
Is larger than that of an M-type star