ASTRONOMY 1010 FINAL EXAM
QUESTIONS & ANSWERS(RATED A)
Condensation Sequence - ANSWER The order in which chemical compounds transition
from the gas into the solid phase, following the condensation temperature of each
compound
Crystals - ANSWER Small pieces of solid material where every atom sits in a well-
defined place, in a very orderly fashion. Once you know where one atom is located, you
know the exact positions of all other atoms.
Jovian - ANSWER Gas giants made up mostly of hydrogen, hydrogen compounds, and
gases. Something similar to the planet Jupiter in composition and size although a range
of compositions and sizes is implied by this term
Differentiation - ANSWER The process of chemical separation of elements based on
their density; higher density materials end up closer to the center of a planet or moon
than lower density materials
Minerals - ANSWER Small or large pieces of material when every atom is surrounded
by a specific set of neighbors, but minerals are not perfectly ordered like crystals,
Compare minerals to crystals as ordinary glass to crystal glass.
Refractory metals - ANSWER Solid materials that can withstand very high temperatures
(they have high melting points)
Rocks - ANSWER Collections of minerals, but not necessarily of the same mineral
Stones - ANSWER Small rocks
Terrestrial - ANSWER Small made mostly of metals and rock. Describes a rocky, Earth-
like planet. It can be lifeless, does not need to have an atmosphere, but it must consist
of rock. The interiors can be liquid rock or solid rock
What are the first materials to condense in the collapsing cloud? - ANSWER Refractory
materials that can withstand the heat of the forming star. Tungsten and osmium
condense first at temperatures just below 1500K.
What gives Mars its reddish color? - ANSWER Mars's surface is abundant with iron
oxide (FeO); we know this compound as rust.
How is the density of a material related to its melting point? - ANSWER The materials
that have the highest melting points are the materials where the atoms bond together
the strongest and are therefore the best able to withstand the higher temperatures. The
, stronger the bond, the closer together the atoms will be, which results in the highest
densities (density is a measure of how tightly atoms are packed together). Thus, high
density silicates, for instance, will precipitate at much higher temperatures than low
density silicates.
Why are there no large planets beyond Neptune? - ANSWER The density of the
building blocks is so low far away from the sun that it takes much longer to accrete a
planet. But the amount of time was simply not available once a proto-star with strong
stellar winds formed at the heart of the nebula.
Why are transits of exoplanets so useful in determining their properties? - ANSWER
When an exoplanet transits, we know that the orbital inclination is very low so that we
can determine the mass of the planet rather than a lower limit. We can also measure
the size of the planet, so we can calculate the density of the planet, which reveals
details about its composition. We can also directly observe the atmosphere of the
planet.
What method/physical phenomenon is at the heart of the detection of exoplanets? -
ANSWER The Doppler shift of light when the light source is moving relative to us along
the line of sight.
Exoplanet - ANSWER A planet orbiting a star other than our Sun
"Hot Jupiter" - ANSWER A gas giant orbiting its host star within approximately 1 AU
Transit light curve - ANSWER The changing brightness of a star shown as a function of
time displaying the dimming of the star when the planet transits in front of it.
Doppler Shift - ANSWER The change in color of light as the source is moving towards
us or away from us
"Super-Earth" - ANSWER Rocky planet larger than our Earth orbiting in extrasolar
planetary systems
How can Kepler's third law be modified so it can be applied to different stellar systems?
- ANSWER Technically, the law does not need to be modified since it contains the mass
of the object that is being orbited, not the Sun's mass. But if we wish to recast it in an
easier form, such as p2 = a3 with p measured in years and a in AUs, then we need to
introduce a pre-factor. This pre-factor is inversely proportional to the mass of the star.
For example, if the star is twice as massive as the Sun, the pre-factor becomes 0.5: p2
= 0.5 a3
Suppose you are tasked with observing our moon for ten consecutive days at the same
time every day. On the first day of your observation, should the moon be close to the
western or to the eastern horizon? - ANSWER Closer to the western horizon. The moon
QUESTIONS & ANSWERS(RATED A)
Condensation Sequence - ANSWER The order in which chemical compounds transition
from the gas into the solid phase, following the condensation temperature of each
compound
Crystals - ANSWER Small pieces of solid material where every atom sits in a well-
defined place, in a very orderly fashion. Once you know where one atom is located, you
know the exact positions of all other atoms.
Jovian - ANSWER Gas giants made up mostly of hydrogen, hydrogen compounds, and
gases. Something similar to the planet Jupiter in composition and size although a range
of compositions and sizes is implied by this term
Differentiation - ANSWER The process of chemical separation of elements based on
their density; higher density materials end up closer to the center of a planet or moon
than lower density materials
Minerals - ANSWER Small or large pieces of material when every atom is surrounded
by a specific set of neighbors, but minerals are not perfectly ordered like crystals,
Compare minerals to crystals as ordinary glass to crystal glass.
Refractory metals - ANSWER Solid materials that can withstand very high temperatures
(they have high melting points)
Rocks - ANSWER Collections of minerals, but not necessarily of the same mineral
Stones - ANSWER Small rocks
Terrestrial - ANSWER Small made mostly of metals and rock. Describes a rocky, Earth-
like planet. It can be lifeless, does not need to have an atmosphere, but it must consist
of rock. The interiors can be liquid rock or solid rock
What are the first materials to condense in the collapsing cloud? - ANSWER Refractory
materials that can withstand the heat of the forming star. Tungsten and osmium
condense first at temperatures just below 1500K.
What gives Mars its reddish color? - ANSWER Mars's surface is abundant with iron
oxide (FeO); we know this compound as rust.
How is the density of a material related to its melting point? - ANSWER The materials
that have the highest melting points are the materials where the atoms bond together
the strongest and are therefore the best able to withstand the higher temperatures. The
, stronger the bond, the closer together the atoms will be, which results in the highest
densities (density is a measure of how tightly atoms are packed together). Thus, high
density silicates, for instance, will precipitate at much higher temperatures than low
density silicates.
Why are there no large planets beyond Neptune? - ANSWER The density of the
building blocks is so low far away from the sun that it takes much longer to accrete a
planet. But the amount of time was simply not available once a proto-star with strong
stellar winds formed at the heart of the nebula.
Why are transits of exoplanets so useful in determining their properties? - ANSWER
When an exoplanet transits, we know that the orbital inclination is very low so that we
can determine the mass of the planet rather than a lower limit. We can also measure
the size of the planet, so we can calculate the density of the planet, which reveals
details about its composition. We can also directly observe the atmosphere of the
planet.
What method/physical phenomenon is at the heart of the detection of exoplanets? -
ANSWER The Doppler shift of light when the light source is moving relative to us along
the line of sight.
Exoplanet - ANSWER A planet orbiting a star other than our Sun
"Hot Jupiter" - ANSWER A gas giant orbiting its host star within approximately 1 AU
Transit light curve - ANSWER The changing brightness of a star shown as a function of
time displaying the dimming of the star when the planet transits in front of it.
Doppler Shift - ANSWER The change in color of light as the source is moving towards
us or away from us
"Super-Earth" - ANSWER Rocky planet larger than our Earth orbiting in extrasolar
planetary systems
How can Kepler's third law be modified so it can be applied to different stellar systems?
- ANSWER Technically, the law does not need to be modified since it contains the mass
of the object that is being orbited, not the Sun's mass. But if we wish to recast it in an
easier form, such as p2 = a3 with p measured in years and a in AUs, then we need to
introduce a pre-factor. This pre-factor is inversely proportional to the mass of the star.
For example, if the star is twice as massive as the Sun, the pre-factor becomes 0.5: p2
= 0.5 a3
Suppose you are tasked with observing our moon for ten consecutive days at the same
time every day. On the first day of your observation, should the moon be close to the
western or to the eastern horizon? - ANSWER Closer to the western horizon. The moon
