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Chapter 10

Terms in this set (68)

An exoplanet eclipse occurs when the exoplanet passes
behind its host star. Qualitatively describe the level of the light curve expected (relative to that which is shown) when the exoplanet is in eclipse and why.
Level of light curve would be in between the high and low plateaus
since the planet does contribute some light (but not as much as the star's), and so its eclipse would remove its contribution.
Suppose our Sun was being monitored from a distant
solar system. By how much would the Sun's light appear
to diminish if Jupiter transited right across the centre of
the Sun? Note that Jupiter's diameter is 1/10 the diameter of the Sun.
The amount of light that would be blocked by Jupiter's disk depends on Jupiter's area which is proportional to its diameter square. As a result, the Sun's light would diminish by (1/10)2 or 1/100 or 1%.
Given that our solar system is 4.5 Gyr (billion years) old,
the Universe is nearly 14 Gyr old, and there are an
estimated 100 billion habitable planets in our Galaxy, is the
hypothesis that humans are the most advanced species in our Galaxy plausible?
This hypothesis is not plausible. There are billions of habitable
planets older than our own in our Galaxy some many billions of years older than our own planets on which life could have evolved. To
imagine that we are the most highly advanced intelligence species atthis stage of our Galaxy's history appears to contradict the Principle of Mediocrity
Around 4 billion years ago Venus could have been more Earth like with liquid water on its surface because
the Sun was dimmer so Venus would have received less radiation
Why does the Sun brighten with time?
as hydrogen is converted into helium in the core, the number of hydrogen nuclei decreases, decreasing the fusion rate. To maintain the balance with gravity pressing inward, the core compensates by shrinking and heating up
Overall, the likelihood of finding planets in a star's habitable zone depends on the
width of the zone
most of the water that used to be present in the Venusian atmosphere
was destroyed in the atmosphere by ultraviolet light from the Sun
the range of distances that has remained habitable for the entire duration of the Sun's lifetime is referred to as the
continuously habitable zone
most of the carbon dioxide on the Earth
is locked up in carbonate rocks in its crust or is dissolved in the oceans
if we allow for a planet with a thick atmosphere and a strong greenhouse effect, the outer boundary of the Sun's habitable zone would be
well beyond the orbital distance of Mars
the term 'global warming' refers to an increase in the average temperature
of the planet as a whole
what is the definition of a star's habitable zone
the range of distances from the star where liquid water can be stable on the surface of a suitable planet
during the last century, sea levels have risen by
about 20 centimeters
europa is located outside the Sun's habitable zone and yet may be habitable. How can this be
Europa is tidally heated, allowing liquid water to exist beneath its icy surface
the atmospheric carbon dioxide concentration
is higher than it has been at any time during the last million years
unlike the Earth, Venus does not have a protective magnetic field because
of its slow rotation
venus is located
outside the Sun's habitable zone
if we do nothing to slow our emissions of carbon dioxide and other greenhouse gases, by the end of the century the global average temperatures are predicted to increase by
3 to 5 oC
the moist greenhouse effect refers to
the warming process by which water vapor rises into the upper atmosphere above the ozone layer where it is then broken apart by ultraviolet radiation
if the Earth were to be moved to where Venus is today
the oceans would evaporate and carbonate rocks would decompose producing a runaway greenhouse effect much more severe than the one that exists on Venus today
stars much more luminous than the Sun have
wider habitable zones, increasing the odds of finding habitable planets but lifetimes too short for life to appear
when the Sun was younger, how did its habitable zone compare with its habitable zone today
narrower and closer to the Sun
over the last century, global temperatures have risen by about
0.8 oC
a star more luminous than our Sun will have a habitable zone that is
wider and farther from the star than the habitable zone of the Sun
if life is present on Venus today, it will most likely be
found in the atmosphere where droplets of water can be found
apart from its distance from its parent star, what is the next most important factor that determines a planet's habitability
the size of the planet
when the Sun runs out of nuclear fuel and expands to become a red giant
the Earth will experience a runaway greenhouse effect followed by the total loss of its atmosphere
which of the following factors influence the surface habitability of a planet
distance from parent star, presence of an atmosphere, planetary size
according to optimistic estimates, the end of habitability of Earth will come about
3 to 4 billion years from now
the possible habitability of Mars today is mostly determined by
geological conditions existing beneath its surface
over time the Sun's habitable zone has
widened and moved away from the Sun
the Moon is in the habitable zone of the Sun at the same distance as the Earth but is not habitable
the Moon is too small to retain an atmosphere necessary for liquid water to be stable
as global warming continues, weather patterns will change causing
some parts of the Earth's landmass to become warmer while other parts will actually get colder. The ocean temperatures will continue to rise
the habitable zone refers to
the range of distances from a star within which a planet could potentially have surface oceans of liquid water
in terms of the gases outgassed by volcanoes, Venus's atmosphere today seems to have
too little water vapor
if Earth were moved to Venus's orbit, it would probably
suffer a runaway greenhouse effect and become hotter than Venus
Venus probably once had as much water (or water vapor) as Earth. What do we think happened to all this water
The water molecules were destroyed, and the hydrogen atoms escaped to space
The reason that some scientists think that Venus might have had oceans early in its history is that
Venus does not show any evidence of two types of crust, like that found on Earth, nor of any ocean basins
The inner boundary of the Sun's habitable zone today is
between the orbit of Venus and the orbit of Earth
Overall, the requirements for a planet to have a habitable surface seem to be
both an orbit within the habitable zone and a size large enough to retain substantial internal heat
What will happen to the Sun's habitable zone in the future
It will move outward
global warming refers to
an increase in Earth's average surface temperature
the current concentration of carbon dioxide in Earth's atmosphere is
significantly higher than it has been for at least several hundred thousand years
is Europa in the Sun's habitable zone
no
Venus's atmosphere has much more carbon dioxide than Earth's because
Venus lacks oceans
in a runaway greenhouse effect, more water begins to evaporate from the oceans, which in turn
increases the strength of the greenhouse effect, causing even more warming
key evidence that Venus once had much more water than it does today comes from
Venus's relatively high ratio of deuterium to ordinary hydrogen atoms
based on all current evidence, if Venus had been born at Earth's distance from the Sun, then Venus today would probably
have oceans and an atmosphere much like Earth
based on current evidence, if Mars had been born at Earth's distance from the Sun, then Mars today would probably
still have a dry surface
which of the following is most likely to render our planet no longer habitable
a runaway greenhouse effect, between about 1 to 3 billion years from now
scientifically speaking, which of the following ideas relevant to global warming is subject to the greatest uncertainty
predictions of future consequences of global warming
carbon dioxide concentration of 400 parts per million (ppm) means that carbon dioxide represents ________ of Earth's atmosphere
less than 0.1%
suppose that Greenland's ice sheet were to melt. What effect would that have on sea level
sea level would rise many meters
Habitable Zone
Volume within which a planet (similar to Earth) could have surface temperatures that permit liquid water on its surface
temperature of planet depends on
distance from its host star, albedo, atmosphere (greenhouse effect), internal heat, tilt of rotation axis and rotation rate
faint young sun paradox
early in Earth's history, the Sun was only 70% as bright as it is
now which would have led to frozen oceans with today's
atmosphere.Yet liquid water has prevailed on Earth's surface throughout its history. Possibly due to excess greenhouse gases
factors influencing habitability
difficult to assign min/max distances of HZ, brighter stars have more distant and wider HZ, fainter stars have narrower HZs, many more times fainter stars than brighter stars
how much has the sun brightened since its formation?
30%
required for hability
be in HZ, planet large enough for plate tectonics (larger than Mars), need atmosphere to permit liquid water on surface
Continuously habitable zone
region that remains habitable from planet's formation, becomes narrower with time
Sun's luminosity increases in the future;
H abundance in core diminishes, leading to slow contraction and heating of core
sun ends life as
a planetary nebula (atmosphere) and white dwarf (core)
the habitable zone now contains which planets
only Earth
the albedo of a surface refers to
the poportion of light it reflects
on Venus, carbon is mainly in the
atmosphere
why is plate tectonics important for habitability?
it regulates climate
The Zone that remains habitable from a star's formation is called
the continuously habitable zone
Global temperatures have risen by how much in the past century
0.8 degrees Celsius
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