ASTRO MIDTERM 2
using the transit method, how many times must a dip in the brightness of a star be observed before it can qualify as an actual planet detection?
3 times
which of the following statements about the greenhouse effect is true?
A) without the naturally occurring greenhouse effect, earth would be too cold to have liquid oceans, B) a weak greenhouse effect operates on mars, C) the burning of fossil fuels increases the greenhouse effect on Earth because of the release of carbon dioxide, D) one result of an increased greenhouse effect on Earth may be an increased number of severe storms
how do the Jovian planets differ from one another?
all have cores about the same mass, but differ in the amount of surrounding hydrogen and helium
how do we think the "hot Jupiters" and other stars were formed?
they formed as gas giants beyond the fros line and then migrated inwards
Why do we think Mercury has so many tremendous cliffs?
they were probably formed by tectonic stresses when the entire planet shrank as its interior cooled
which of the following applies to europa?
thought to have a deep, subsurface ocean of liquid water
which feature of this photo of the full moon is one of the lunar Maria
3
In an extrasolar planetary system containing a single planet, the parent star is measured to move about its center of mass every 24 years. Given this, what is the orbital period of the planet?
24 years
Suppose Earth's atmosphere had no greenhouse gases. Then Earth's average surface temperature would be
-16 degrees celsius, which is well below freezing
in order to be able to directly see the sun's motion due to Jupiter's gravity, an observer at a distance of 10 light-years would need to be able to measure changes in its position of
0.0005 arc seconds
approximately how large is an impact crater compared to the size of the impactor
10 times larger
the two principal sources for the internal heating of terrestrial planets are
accretion and radioactivity
Why are Saturn's rings so thin?
Any particle in the ring with an orbital tilt would collide with other ring particles, flattening its orbit.
Why do asteroids and comets differ in composition?
Asteroids formed inside the frost line, while comets formed outside.
which photo shows an object that looks most like a typical asteroid?
D
the lunar Maria (seas) were formed by
Extensive volcanic lava flows in the first billion years of the solar system
the first person to claim to see linear features on the surface of mars was
Giovanni Schiaparelli
What is the solar wind?
a stream of charged particles flowing outward from the surface of the Sun
which of the following best describes convection?
It is the process in which warm material expands and rises while cool material contracts and falls.
Why is Mars red?
Its surface rocks were rusted by oxygen.
How does the heat Jupiter radiates compare to the energy it receives from the Sun?
Jupiter radiates back into space about twice the energy it gets from the sun
what causes the "gaps" observed in the asteroid belt between mars and Jupiter?
Jupiter's gravity causes orbital resonances that nudge asteroids out of these areas
Which of the jovian planets have rings?
Jupiter, Saturn, Uranus, Neptune
why is Saturn almost as big as Jupiter, despite its smaller mass>
Jupiters greater mass compresses it more and increases its density
How did the lunar maria form?
Large impacts fractured the Moon's lithosphere, allowing lava to fill the impact basins.
Rank the five terrestrial worlds in order of size from smallest to largest.
Moon, mercury, mars, Venus, earth
What do asteroids and comets have in common?
Most are unchanged since their formation in the solar nebula.
Will Pluto eventually collide with Neptune?
No, because the two planets have an orbital resonance that prevents them from colliding.
A star is seen to have two transiting planets. Planet 1 transits every 3 months, and Planet 2 transits every 15 months. What can we infer about their orbits?
Planet 2's semi major axis is larger than Planet 1's
Direct detection of an extrasolar planet means ________.
acquiring images or spectra of the planet
Why is Jupiter denser than Saturn?
The extra mass of Jupiter compresses its interior to a greater extent than that of Saturn.
What is the origin of Jupiter's moons?
The four Galilean moons formed with Jupiter, most others were later captures
Why do Uranus and Neptune appear blue?
The methane gas in their atmospheres absorbs all colors except blue
Which of the following is not evidence for the existence of water on the Martian surface in the past of today?
The sublimation of the Martian polar caps
imagine that you are trying to stop neutrinos with a lead shield. how thick would you need to make this shield to ensure that it can stop an average neutrino?
about one light-year
Which moon did the Huygens spacecraft land on?
Titan
on average, how fast do the (tectonic) plates move on earth?
a few centimeters per year
What is the Great Red Spot?
a long-lived, high-pressure storm on Jupiter
What is a so-called "hot Jupiter"?
a planet with a mass similar to Jupiter but very close to the central star and therefore hot
why do most scientists accept the claim that climate change is being caused by human activity
all of the above: A) Levels of atmospheric carbon dioxide show a sharp increase since the industrial revolution.B) Computer models correctly reproduce past climate variations.C) Computer models that include the effects of human activity correctly predict the current trend of increasing temperatures.D) Computer models that do not include the effects of human activity do not correctly predict the current trend of increasing temperatures.
Suppose you view the solar system from high above Earth's North Pole. Which of the following statements about planetary orbits will be true?
all the planets orbit counterclockwise around the sun
Where are the Trojan asteroids located?
along Jupiter's orbit, 60° ahead of and behind Jupiter
seasons on mars
are similar to those on the Earth but twice as long
what must be true about the orbit of a planet discovered by the transit method?
as seen from earth, the planet's orbit must be nearly parallel to our line of sight
the first planets around other sun-like stars were discovered
at the end of the 20th century
Why does Mars have more extreme seasons than Earth?
because it has a more eccentric orbit
How have we been able to construct detailed maps of surface features on Venus?
by using radar from spacecraft that were sent to orbit Venus
the atmosphere of mars is mostly made of
carbon dioxide
Earth's atmosphere contains only small amounts of carbon dioxide because
carbon dioxide dissolves in water, and most of it is now contained in the oceans and carbonate rocks
the seasonal polar caps on mars which appear and disappear with the seasons are mars are made of
carbon dioxide ice
Based on our current theory of Earth's formation, the water we drink comes from
comets that impacted earth
The core, mantle, and crust of a planet primarily have differences in their
density
which of the following methods has lead to the most discoveries of extrasolar planet candidates?
detecting the dip in measured brightness as the planet crosses our line of sight to the star
Why does Jupiter have several distinct cloud layers?
different layers represent clouds made of gases that condense at different temperatures
How can astronomers currently determine the temperature of an extrasolar planet?
estimate the temperature based on the planets distance from the star AND measure the drop in total infrared light when the planet basses behind the star from our perspective
What are greenhouse gases?
gases that absorb infrared light
the northern hemisphere of mars has fewer craters than the southern hemisphere. this indicates that
geologic processes have resurfaced much of the northern hemisphere
what field of science are the experiments on the Mars Rovers Sojourner, Spirit, Opportunity and Curiosity most closely related to?
geology
What two physical processes balance each other to create the condition known as gravitational equilibrium in stars?
gravitational force and outward gas pressure
A planet is most likely to have tectonic activity if it has
high internal temperature
spectra of the martian surface taken from orbiting spacecraft have detected the presence of which of the following minerals that form in water?
hydrated clays, sulfates and silicates
how does earth's magnetosphere affect our atmosphere?
it deflects solar wind particles that would otherwise strip away the atmosphere
why is the asteroid Ceres now considered to be a dwarf planet?
it is large enough to be round
the graph on the right shows the brightness of a star over the course of a transit. which of the following do we learn about the planet?
it is large enough to block about 2.5% of the star's light
according to the nebular theory, how did the asteroid belt form?
it is made of planetesimals between the orbits of mars and Jupiter that never formed a planet
which of the following statements about titan is not true?
it is the coldest moon in the solar system
Why does Earth have the strongest magnetic field among the terrestrial worlds?
it is the only one that has both a molten metallic outer core and reasonably rapid rotation
what is the importance of the carbon dioxide (CO2) cycle?
it regulates the carbon dioxide concentration of our atmosphere, keeping temperatures moderate
which of the following has virtually no effect on the internal structure of a planet?
its magnetic field
Based on all we know about the terrestrial worlds, what single factor appears to play the most important role in a terrestrial planet's geological destiny?
its size
what is the main reason that mars, compared to earth, has become so geologically inactive?
its size
valles marineris is a(n)
large canyon on Mars.
According to our theory of solar system formation, what are asteroids and comets?
leftover planetesimals that never accreted into planets
the graph shows how a star's orbit speed (radial velocity) caries with time due tot he gravitational tug of an orbiting planet. the amplitude of the radial velocity is related to the planet's______
mass
the doppler technique can be used to estimate the semimajor axis of a planet's orbit by
measuring the time it takes for the star's line-of-sight velocity to cycle from peak to peak, and using Newton's version of Kepler's third law
Spacecraft have landed on all the terrestrial worlds except
mercury
Where is Jupiter's strong magnetic field generated?
metallic hydrogen layer
the terrestrial planet cores contain mostly metal because
metals sank to the center during a time with the interiors were molten throughout
By what process does the Sun generate energy?
nuclear fusion
which of the following is not a method astronomers use to determine the physical conditions inside the sun?
observing x ray images of the solar interior using satellites
which of the following gases best absorbs ultraviolet light?
ozone
Which new idea has been added into our theory of solar system formation as a result of the discoveries of extrasolar planets?
planets can migrate from the orbits in which they are born
What is the chief difficulty in attempting to detect planets around other stars?
planets do not emit visible light, and they are typically at least a billion times fainter than their host stars
which of the following is the phase of matter in the interior of the sun?
plasma
which of the following does not lend support to the idea that Pluto is a Kuiper-belt object?
pluto is smaller than many known comets, such as Halley's Comet
the graph on the right shows how a star's orbital speed varies with time due tot he gravitational tug of an orbiting planet. these data were observed by measuring the ____
precise wavelengths of spectral lines in the spectrum of the star
how can primitive meteorites be distinguished from processed meteorites?
radiometric dating shows that primitive meteorites are slightly older
which of the following methods has been at least successful in detecting extrasolar planets around other star systems?
regular changes in the positions of the parent stars with respect to more distant stars as they move across the sky
which statement about planetary rings in not true
saturn's rings formed along with its moons 4.8 billion years ago
the light radiated from the sun's surface reaches earth in about 8 minutes. however, the energy of this light was released by fusion in the sun's core about
several hundred thousand years ago
Sunspots are cooler than the surrounding gas in the photosphere because
strong magnetic fields slow convection and prevent hot plasma from entering the region
the process of making an inhabitable planet like mars habitable and suitable for humans is referred to as
terraforming
Each white dot in the figure on the right represents the location of a small body in our solar system. The donut shaped ring of white dots just beyond Neptune's orbit represents the part of our solar system that we call:
the Kuiper belt
which of the following can act like a long-term "thermostat" for the Earth's average temperature?
the carbon dioxide cycle
what does the figure below tell us?
the current level of carbon dioxide in our atmosphere is higher than it has been at any time during the past 800,000 years
which of the following best describes tectonics?
the disruption of a planet's lithosphere by internal stresses
the diagram on the right shows the orbital path of the sun around the center of mass of our solar system as it would appear from a distance of 30 light years for the period of 1960-2025. if aliens had constructed this graph at their home star system, they could learn all of the following except
the fact that the large icy objects orbit the sun in the Kuiper belt
the planet CAROT-14b is only slightly larger than Jupiter, but several times more massive. What is the possible explanation for its similar size to Jupiter?
the hydrogen and helium gas compressed under their own gravity to a higher density than Jupiter
which of the following statements is an overall summary if the findings from the viking biology experiments on mars?
the martian soil is chemically reactive but shows no signs of biological activity
Study the figure above and its axis labels. What is this graph showing us?
the number of sunspots on the sun tends to increase and decrease with an approximately 11 year cycle
Kirkwood gaps in the asteroid belt occur at distances where
the period of an orbiting asteroid would be a simple fraction (like 1/3 or 1/4) of Jupiter's orbital period
What is orbital resonance?
the periodic gravitational interaction of two orbiting bodies on one-another resulting in changes in the two bodies' orbits
You observe a star very similar to our own Sun in size and mass. This star moves very slightly back and forth in the sky once every 4 months, and you attribute this motion to the effect of an orbiting planet. What can you conclude about the orbiting planet?
the planet must be closer to the earth than It is to the sun
according to the current understanding, which of the following is required for a planet to have rings that last for. a very long time?
the planet must have many small moons that orbit relatively close to the parent in its equatorial plane.
the depth of the dip in a star's brightness due tot he transit of a planet depends most directly on
the planet's size
which of the following is not due to tidal forces?
the retrograde orbit of Triton
the lithosphere of a planet is the layer that consists of
the rigid rocky material of the crust and uppermost portion of the mantle
Why does the plasma tail of a comet always point away from the Sun?
the solar wind pushes the plasma ions directly away from the sun
When we see a region of a planet that is not as heavily cratered as other regions, we conclude that
the surface in the region is younger than the surface in the more heavily cratered regions
which observations characterize solar maximum?
there are many sunspots visible on the surface of the sun
If Saturn had no moons, what do you suppose its rings would look like? Why is this?
there would be no rings
Jupiter and the other jovian planets are sometimes called "gas giants." In what sense is this term misleading?
they actually contain relatively little material in a gaseous state
which of the following is not a general characteristic of the four Jovian planets in our solar system?
they are higher in average density than the terrestrial planents
what is the origin of martian meteorites?
they are rocks blasted from the surface of Mars by impacts; these rocks then floated around in interplanetary space before falling to Earth
the photo on the right shows
valles marineris on mars
which of the following best describes the composition of particles forming Saturn's rings
water ice
The relatively few craters that we see within the lunar maria
were formed by impacts that occurred after those that formed most of the craters in the lunar highlands
what are the circumstances under which convection can occur in a substance?
when the substance is strongly heated form underneath
