ASTRO 1345 CH. 9 QUESTIONS WITH CORRECT ANSWERS LATEST UPDATE 2025/2026
Why is Venus visible only before sunrise or after sunset? Maximum for how long (in hours)
Venus is visible in the sky? - Answers Its orbit lies within Earth's, so Venus, like Mercury, is
always found fairly close to the Sun in the sky. Never seen more than 47 degrees from the Sun.
Given Earth's rotation rate of 15 degrees per hour, this means that Venus is visible above the
horizon for at most 3 hours before the Sun rises or after it sets.
List the three brightest objects in order in the sky. - Answers From least to greatest
-Venus
-Moon
-Sun
Why does Venus appear so bright? How much sunlight does it reflect back? - Answers Venus is
highly reflective. Nearly 70 percent of the sunlight reaching Venus is reflected back into space.
Most of the light is reflected from clouds in the atmosphere.
Because Venus orbits between Earth and the Sun, Venus is full when it is at its greatest distance
from us-1.7 AU away on the other side of the sun.
If we compare the radius, how big is Venus compared to the Earth? - Answers At 0.28 AU,
Venus's angular diameter is 64". From this observation, we can determine the planet's radius to
be about 6000 km. More accurate measurements from spacecraft give a value of 6052 km, or
0.95 Earth radii.
How massive is Venus as compared to the Earth? - Answers Note: Venus has no moon. Mass
was usually indirectly measured by gravitational effect on small objects.
Venus has a mass of 4.9*10^24 kg, or 0.82 the mass of Earth.
How dense is Venus as compared to the Earth? - Answers From its mass and radius, we find
that Venus's average density is 5200 kg/m^3.
Why do we say that Venus is similar to the Earth in terms of bulk properties? - Answers If the
planet's overall composition were similar to Earth's as well, we could then reasonably conclude
that Venus's internal structure and evolution were basically earth-like. But because it isn't, we
only focus on the bulk properties.
(Rotation Rate) How much time does Venus take to spin (rotate) on its own axis? - Answers
Because of the ever-changing nature of the clouds, astronomers had a difficult time finding the
, rotation rate. With the use of a Doppler radar, the echoes implied that the rotation came out to
be a sluggish 243-day period.
What do you imply from the retrograde motion of Venus? - Answers It is spinning in a sense
opposite that of Earth and most other solar system objects and opposite that of Venus's orbital
motion.
In what direction does Venus spin as compared to other planets? - Answers Other planets
always rotate from west to east. With this definition, Venus's retrograde spin means that the
planet's north pole lies below the plane of the ecliptic, unlike any of the other terrestrial worlds.
How much of the axis of Venus is tilted towards the ecliptic? - Answers Venus's axial tilt- the
angle between its equatorial and orbital planes is 177.4 degrees compared with 23.5 degrees in
the case of Earth.
Compare the Venus day with the Venus year. - Answers Because of the planet's slow retrograde
rotation, its solar day (from noon to noon) is quite different from its sidereal rotation period of
243 Earth days (the time of one true rotation relative to the stars). One Venus day is a little more
than half a Venus year (225 earth days)
Exactly how many times does Venus rotate on its axis from its one closest to its next closest
approach in its orbit to earth? - Answers Venus spins so slowly because it has been theorized
that in its evolution it got struck by a large body which reduced its spin to almost zero. It rotates
almost exactly five times between one closest approach to Earth and the next. As a result,
Venus always presents nearly the same face to Earth at closest approach.
(Long distance observations of Venus) Why is Venus called Earth's sister planet? - Answers
Because Venus most nearly matches Earth in:
-size
-mass
-density
Why did early studies of Venus lead astronomers to taking such inaccurate pictures of Venus's
surface conditions? - Answers They believed that the cloud cover was mostly water vapor and
began hoping that life could be sustainable there. Without equipment that picks up radiation
rays, astronomers believed that the surface temperature was only 20 degrees higher than
Earth's. Using radio waves, it was discovered that Venus was an arid desert.
(The surface of Venus) How much of the area of Venus is covered with elevated continents,
lowlands, and rolling plains? - Answers Magellan has provided sharper views of Venus's surface.
Notable continent sized features include Ishtar Terra and Aphrodite Terra.
Why is Venus visible only before sunrise or after sunset? Maximum for how long (in hours)
Venus is visible in the sky? - Answers Its orbit lies within Earth's, so Venus, like Mercury, is
always found fairly close to the Sun in the sky. Never seen more than 47 degrees from the Sun.
Given Earth's rotation rate of 15 degrees per hour, this means that Venus is visible above the
horizon for at most 3 hours before the Sun rises or after it sets.
List the three brightest objects in order in the sky. - Answers From least to greatest
-Venus
-Moon
-Sun
Why does Venus appear so bright? How much sunlight does it reflect back? - Answers Venus is
highly reflective. Nearly 70 percent of the sunlight reaching Venus is reflected back into space.
Most of the light is reflected from clouds in the atmosphere.
Because Venus orbits between Earth and the Sun, Venus is full when it is at its greatest distance
from us-1.7 AU away on the other side of the sun.
If we compare the radius, how big is Venus compared to the Earth? - Answers At 0.28 AU,
Venus's angular diameter is 64". From this observation, we can determine the planet's radius to
be about 6000 km. More accurate measurements from spacecraft give a value of 6052 km, or
0.95 Earth radii.
How massive is Venus as compared to the Earth? - Answers Note: Venus has no moon. Mass
was usually indirectly measured by gravitational effect on small objects.
Venus has a mass of 4.9*10^24 kg, or 0.82 the mass of Earth.
How dense is Venus as compared to the Earth? - Answers From its mass and radius, we find
that Venus's average density is 5200 kg/m^3.
Why do we say that Venus is similar to the Earth in terms of bulk properties? - Answers If the
planet's overall composition were similar to Earth's as well, we could then reasonably conclude
that Venus's internal structure and evolution were basically earth-like. But because it isn't, we
only focus on the bulk properties.
(Rotation Rate) How much time does Venus take to spin (rotate) on its own axis? - Answers
Because of the ever-changing nature of the clouds, astronomers had a difficult time finding the
, rotation rate. With the use of a Doppler radar, the echoes implied that the rotation came out to
be a sluggish 243-day period.
What do you imply from the retrograde motion of Venus? - Answers It is spinning in a sense
opposite that of Earth and most other solar system objects and opposite that of Venus's orbital
motion.
In what direction does Venus spin as compared to other planets? - Answers Other planets
always rotate from west to east. With this definition, Venus's retrograde spin means that the
planet's north pole lies below the plane of the ecliptic, unlike any of the other terrestrial worlds.
How much of the axis of Venus is tilted towards the ecliptic? - Answers Venus's axial tilt- the
angle between its equatorial and orbital planes is 177.4 degrees compared with 23.5 degrees in
the case of Earth.
Compare the Venus day with the Venus year. - Answers Because of the planet's slow retrograde
rotation, its solar day (from noon to noon) is quite different from its sidereal rotation period of
243 Earth days (the time of one true rotation relative to the stars). One Venus day is a little more
than half a Venus year (225 earth days)
Exactly how many times does Venus rotate on its axis from its one closest to its next closest
approach in its orbit to earth? - Answers Venus spins so slowly because it has been theorized
that in its evolution it got struck by a large body which reduced its spin to almost zero. It rotates
almost exactly five times between one closest approach to Earth and the next. As a result,
Venus always presents nearly the same face to Earth at closest approach.
(Long distance observations of Venus) Why is Venus called Earth's sister planet? - Answers
Because Venus most nearly matches Earth in:
-size
-mass
-density
Why did early studies of Venus lead astronomers to taking such inaccurate pictures of Venus's
surface conditions? - Answers They believed that the cloud cover was mostly water vapor and
began hoping that life could be sustainable there. Without equipment that picks up radiation
rays, astronomers believed that the surface temperature was only 20 degrees higher than
Earth's. Using radio waves, it was discovered that Venus was an arid desert.
(The surface of Venus) How much of the area of Venus is covered with elevated continents,
lowlands, and rolling plains? - Answers Magellan has provided sharper views of Venus's surface.
Notable continent sized features include Ishtar Terra and Aphrodite Terra.
