astronomy 1101 final
the radial velocity / doppler shift method works because....
a star and its planets orbit the common center of mass
the speed of light is about 300,000,000 METERS/s. Mars is often about 300 million KILOMETERS from earth. how long does it take to send a radio message from earth to mars (one way) when mars is this far away?
about 1000 seconds
how do force, mass, and acceleration relate?
acceleration felt by an object depends directly on force exerted on it and inversely on its mass
where do most nearby stars appear in an HR diagram plotting luminosity vs temp?
along a narrow stripe with temp and luminosity tracking one another
if you took the earth and moved it 5 times farther away from the sun, what would happen to the strength of the force of the sun's gravitational pull on the earth?
it would go down by a factor of 25
which of these cannot be estimated from carefully analyzing the light received from an astronomical object?
its age
which of these is not true about the sun as a red giant star?
its core is much cooler than the core of the current sun
what is the main property that determines the luminosity of a main sequence star?
its mass
what is the main determinant of the present day interior temp of a planet?
its size
compared to green light, infrared light has.....
lower frequency, higher wavelength, lower energy
which of these is not true about neutron stars?
massive versions of neutron stars live at the centers of most galaxies
Object A has a mass of 1 kg. Object B has a mass of 20 kg. If the same force is applied to both....
B will have 1/20th the acceleration of A
what happens to the temp of an object that contracts under the influence of gravity?
it goes up, the object heats up
what is not true about Milky Way galaxy?
it is the largest structure that we know of in the universe
a comet moves through solar system on a highly elliptical orbit. as the comet moves from Oort Cloud, in past Pluto, and gets closer to the sun, what happens to its speed?
it speeds up
Which is not true about Ptolemy's geocentric model describing the motions of the planets?
it was simple
which of these is not true about the fate of a star 10 times the mass of the sun?
it will collapse directly into a black hole
to place a star in the HR diagram, which of these measurements is necessary?
measure the radial velocity via the doppler shift
which of these is NOT true about the history of discovering planets outside the solar system?
most exoplanets are known from directly imaging (taking pictures) of them
The largest blow Galileo dealt to the Ptolemaic system was to show that Venus appears
nearly full when closest
what is not true about Ptolemy's model of universe?
new stars constantly appear and disappear in the heavens
the whirlpool galaxy is about 20 million light years away from earth, towards the virgo cluster. is it possible that scientists in the virgo galaxy know about modern humans?
no
which of the following is true about nuclear fusion and fission?
nuclear fusion releases energy when fusing light elements
Two bodies (A and B) have the same angular size from your position, but B is twice as far away as A. Which is physically larger?
object B
two bodies (a and b) have the same physical size, but B is twice as far away from A. which one appears smaller and by how much?
object B appears 2x smaller than A
which of these is not true about the force of gravity between two objects?
only the less massive object feels gravitational pull
the planets in our solar system....
orbit in the same plane and spin in the same direction
what is not true about apparent motion of planets in the sky?
planet stay approximately fixed relative to the background stars. mars stays in ares, jupiter in Cetus, etc
what does the doppler/radial velocity planet detection technique tell us about a planet?
planet's orbital period and mass
which of these is not true about the true orbits of planets?
planetary orbits are circular in shape
order the following types of light from low to high frequency
radio, infrared, ultraviolet, x-ray
how does a rocket work?
rocket expels material at high velocity and the equal and opposite force accelerates the rocket
Compared to Jovian planets, terrestrial planets are:
rockier, found closer to the sun, denser, less massive
all other things being equal, what cools off faster: a big object or a small object (assuming they are both spheres starting at same initial temp)?
small object
what is the fastest that anything can move?
speed of light
star twosun has two times the mass of the sun and 8 times the luminosity of the sun. how does the main sequence lifetime of star twosun compare to that of the sun?
star twosun has a 4 times shorter lifetime than the sun
what is not true about stellar parallax and debate between geocentric and heliocentric cosmologies?
stars do not show any parallax at all
which of these is not true about star clusters?
stars in a cluster all have the same mass
which of these is true about star birth?
stars often form in binary or triple systems
which of these statements about dates is NOT correct?
stellar parallaxes were first measured around 1600 CE
on a day of a full moon, the moon rises when?
sunset
which of these is not an advantage of telescopes over naked eye observation?
telescopes immediately show how far away something is, while human eyes do not
which of these is NOT true about the forces acting inside a main sequence star (like the sun)?
the balances of forces is delicate. a small change in the star's structure will tear it apart
you see two hot opaque objects. one glows blue, the other glows red. which is true?
the blue object is hotter than the red object
if we could take a spectrum of an earth-like planet, the sharp spectral features in its atmosphere could tell us directly about.....
the chemical makeup of its atmosphere and possible presence of life
what is nuclear fusion?
the combination of two atomic nuclei from a heavier nucleus of a new element
what is the closest to the diameter of the earth?
10,000 km
how does a white dwarf change as it ages?
it cools off, losing residual heat an becoming dimmer
according to our current best estimates, about what fraction of stars have an earth-sized planet in their habitable zone?
10%
the first radio broadcasts left earth in around 1900. how far away is the most distant alien civilization that could know about us from our broadcasts?
100 light years (2018-1900=118)
there are 10,000 big galaxies in the coma cluster. if each has a bout 100 billion stars, how many stars are there in the coma cluster?
10^15 10,000 is 10^4. 100,000,000,000 is 10^11. 10^11 x 10^4 = 10^15
about how old is the universe?
14 billion years
about how far is it from the sun to nearest other stars?
4 light years
about how old is the sun?
4.5 billion years
how old is the sun?
4.5 billion years
what was Copernicus' major contribution to the development of astronomy?
Copernicus made first modern arguments for sun-centered universe
what is the key contribution of Johannes Kepler to understanding of cosmology?
Kepler built a mathematic heliocentric model that provides superior predictions for planetary positions compared to geocentric models
what was Isaac Newton's role in development in astronomy?
Newton developed physical explanation for the laws of planetary motion derived by Kepler
what happens to a white dwarf that exceeds the Chandrasekhar mass?
it explodes in a thermonuclear supernova
what is not true about Tycho Brahe and his contributions to astronomy?
Tyco carried out the best pre-telescope observing campaign
over the course of a year, you measure the parallax of Vega to be one Half the parallax of Proxima Centauri. what does this tell us?
Vega is twice as far away as proxima centauri
the earliest telescopes were refracting telescopes. which of these describes how such telescopes operate?
a lens bends the path of light, collecting light rays from across large area at eye
what is a black hole?
an object from which no light can escape
how do apparently brightness, luminosity, and distance of an object relate?
apparent brightness depends linearly on the luminosity and inversely on the square of the distance
which of these describes parallax?
as an observer changes location, the apparent position of a distant object changes
which of these is not true of the expected fate of the sun?
at the end of its life, the sun will explode as a supernova
how do we know the age of the sun? most likely answer
by using radioactive decay to measure the age of rocks created during the formation of the solar system
which is one way that we know about the existence of black holes?
by watching visible stars orbit around invisible objects
which of these is NOT true about binary star systems and cosmic explosions?
core collapse (massive star) supernova probably requires binary companion
a light year is the unit of
distance
x-rays move faster than infrared light
false
the planets in our solar system formed....
from a spinning disk of gassed dust around the young sun
what was Galileo's role in development of astronomy?
galileo was first person to use telescope to study astronomical objects
how did Aristotle infer the shape of the earth based on observations of lunar eclipses?
he observed a circular shadow and argued that the earth must be a sphere
which of these is not true about high and low mass stars?
high mass stars are more common than low mass stars
what is the sun mostly made of ?
hydrogen and helium
what is not true about phases of the moon?
if we wait long enough, every phase is visible from earth at sunrise
based on the daily motions of the stars, sun, and moon, what is a common first cosmology adopted by many ancient people?
imagining the heavenly bodies as affixed to a great rotating dome overhead
where was most o the oxygen in our bodies created?
in a high mass star that exploded as a supernova
where was most of the iron on earth created?
in exploding white dwarf supernova
where is the most mass in the solar system?
in the sun
how have we discovered most of the extrasolar planets that we know about?
indirectly via their influence on light from their parent star
we observe sharp spectral features associated with hydrogen in light from the pinwheel galaxy. in light from the pinwheel, these features appear at 1% longer/larger wavelengths than what we measure for the same features in a lab here on earth. why?
the hydrogen in the pinwheel galaxy is moving away from us
what cannot be seen with the naked eye?
the moons of jupiter
consider a low mass object orbiting a high mass (parent) object. how do the mass of the parent object, size of the orbit, and the orbital speed relate?
the orbital speed is higher for a higher mass parent object and lower for a larger orbit
what does the transit planet detection technique tell us about. a planet?
the planet's orbital period and diameter
what describes structure of universe for Ptolemy, Hipparchus, Aristotle, and their followers?
the planets move on nested spheres centered on the earth
how do orbits let us measure masses?
the speed and radius of orbits can be observed, and together these determine the mass causing the orbit
which is not true about the eventual fate of a star 50 times the mass of the sun?
the star lives for about the same time as the sun
which of these is true about sun and earth in orbit?
the sun and earth orbit both common center of mass, but sun orbits with a much smaller semi major axis
over the course of a year, what happens to the apparent position of the sun in the sky?
the sun appears to move in a full circle around the sky
what common feature is shared by all main sequence stars?
they all fuse hydrogen into helium at their cores
what goes faster: infrared or radio light?
they go the same speed
which of these describes what educated ancient astronomers knew about the shape of earth by around 200 CE?
they knew that the earth was a sphere and approximate size
what is not true about modern telescopes?
they use lenses to bend and collect light from large area
a star with a high luminosity and low surface temp must be....
very big
why was the discovery of Jupiter-mass planets extremely close to their parent star surprising?
we think that Jovian planets only form in the icy outer solar system
what do we mean when we say telescopes are time machines?
when we receive light from distant object, we see that object as it was in the distant past due to light travel time
which of these is NOT true about white dwarf stars?
white dwarfs can have any mass
is the path of light affected by gravity?
yes
