Quiz 2 Flashcards
What is percent illuminated?
the fraction of the moon’s disk lit as seen from earth
What are the phases of the moon starting at 0% illuminated?
New moon, waxing crescent first quarter, waxing gibbous, full moon, waning gibbous, third quarter, and waning crescent
What is the syndoic month?
The time it takes the moon to complete one orbit around the earth (with respect to the sun) is also the amount of time it takes to complete one cycle of phases
How long is the synodic month?
29.5 days
What three concrete connections can we make about the moon?
the moon’s phases, the time, and the moon’s location in the sky. Any of these two can be used to get the other
What is one thing that changes with the observers location on Earth?
time
Does the sky or observer rotate during the rising and setting of the sky?
Observer
What is the zenith?
The point directly overhead the observer
What is the nadir?
The point directly below the observer
What is the celestial meridian?
the imaginary line that runs in the sky from the north to the south
What is the altitude?
how high it is in the sky
How is an altitude usually measured?
degrees (0 is horizon, 90 is zenith)
What is the celestial equator?
a circle that rises in the east, reaches its highest altitude at the meridian, and sets in the west.
What can be found along the celestial equator?
The sun and the moon
What is Kepler’s first law?
Law of ellipses: The orbit of a planet is an ellipse where one focus of the ellipse is the sun.
Who created the three laws of planetary motion?
Johannes Kepler
Explain more in depth Kepler’s first law.
There are two focus points and the ellipse forms around them. One of these points will always be the sun. The equation is r’1+r’2 = 2a. A is the semimajor axis. The equation for eccentricity is e = c/a
What is the semimajor axis?
The distance from the center of the focii to the edge of the ellipse
What is eccentricity?
How elliptical (oval) the ellipse is. If the ellipse is more circular or flat. You get this by dividing the center of the ellipse to one of the focii (c) by the semimajor axis (a).
What is Kepler’s second law?
Law of equal areas: A line from the planet to the sun sweeps out equal areas in equal amounts of time. Kepler’s second law basically says that the planets speed is not constant – moving slowest at aphelion and fastest at perihelion. The law allows an astronomer to calculate the orbital speed of a planet at any point.
What is the perhelion?
the object is closest to the sun
What is the aphelion?
the object is the furthest from the sun
What is Kepler’s third law?
Law of harmonies: The period of a planet’s orbit squared is proportional to its average distance from the sun cubed. This law only works in our solar system. P^2 = a^3
What is the period?
The average distance of a planet from the sun
How is the period measured?
years
How is the semimajor axis measured?
AU (astronomical units)
What is Newton’s first law?
only a force acting on an object can change its motion
For a planet in an elliptical orbit to “sweep out equal areas in equal amounts of time” it must…
move fastest when near the sun
If a planet is twice as far from the sun at aphelion than at perihelion, then the strength of the gravitational force at aphelion will be _ at it is at perihelion?
one quarter as much
What is acceleration?
The change in velocity
When viewed from above the north pole the earth rotates…
counter-clockwise
When the moon crosses the western side of the horizon plane it is…
setting
When the moon crosses the eastern side of the horizon plane it is…
rising
What is the rising time of the New moon?
6 am
What is the rising time of the Waxing Crescent?
9 am
What is the rising time of the first quarter?
12 pm
What is the rising time of the waxing gibbous?
3 pm
What is the rising time of the full moon?
6 pm
What is the rising time of the waning gibbous?
9 pm
What is the rising time of the third quarter?
12 am
What is the rising time of the waning crescent?
3 am
What is the Meridian crossing time of the new moon?
12 pm
What is the Meridian crossing time of the waxing crescent?
3 pm
What is the Meridian crossing time of the first quarter?
6 pm
What is the Meridian crossing time of waxing gibbous?
9 pm
What is the Meridian crossing time of full moon?
12 am
What is the Meridian crossing time of waning gibbous?
3 am
What is the Meridian crossing time of third quarter?
6 am
What is the Meridian crossing time of waning crescent?
9 am
What is the setting time of the new moon?
6 pm
What is the setting time of the waxing crescent?
9 pm
What is the setting time of the first quarter?
12 am
What is the setting time of the the waxing gibbous?
3 am
What is the setting time of the full moon?
6 am
What is the setting time of the waning gibbous?
9 am
What is the setting time of the third quarter?
12 pm
What is the setting time of the waning crescent?
3 pm
What is the total amount of time between the rising and setting times of the lunar phases?
12 hours. Meaning rising to meridian crossing is 6 hours apart and meridian crossing to setting is another 6 hours. And setting to rising will be 12 hours.
How does the rising, meridian crossing, and setting time change with each lunar phase.
It changes 3 hours every lunar phase change
What is the equation for Newtons law of gravity?
F = GMm/r^2 (F is force, M and m are the masses of the two bodies you use, G is the gravitational constant
What is newton’s version of Kepler’s third law?
P^2 = (4pia^3)/ G(M + m)
What do Newton’s law of motions apply to?
all orbiting bodies
What is the name of Lab 7?
Solar System Models
What is the name of Lab 6?
Stellarium - The Mass of Jupiter
What is the name of Lab 5?
Planetary Orbit Simulator
What is the name of Lab 4?
Lunar Phases
What are models?
representations, which while simplified but retain many key elements
What are some astronomical observations that we see?
All objects in the heavens rise in the east and set in the west, The sun travels around the sky in 24 hours, The stars travel around the sky slightly faster than the sun (23 hours and 56 minutes), There are several thousand stars that we can see at night with good visibility.
What is elongation?
The angle between the sun and the planet
What is the greatest elongation?
the largest elongation the object would reach
What is the greatest elongation of mercury?
28 degrees
What is the greatest elongation of Venus?
48 degrees
What is superior conjunction?
if the sun is in front of the planet
What is inferior conjunction?
if the planet is in front of the sun
Are Venus and Mercury close or far from the sun?
close
Are Mars, Jupiter, and Saturn close or far from the sun?
far
What is the elongation of opposition?
180 degrees
What is the elongation of conjunction?
0 degrees
What is the elongation of quadrature?
90 degrees
How do the planets move?
rotate on a circle, which in turn, rotated around the sun.
In the Ptolemy model what is the smaller circle called?
epicycle
In the Ptolemy model what is the larger circle called?
deferent
What is the idea of heliocentrism?
The planets rotate around the sun
What is the relationship between the distance the planet is away from the sun and its velocity?
The closer it is to the sun the faster it moves, the further away the slower it moves
What observations did Copernicus’ Heliocentric model make?
Like the geocentric model, the earth was believed to be round, The earth rotated, and thus the stars, sun, and planets appeared to move around the earth Mercury and Venus were closer to the sun than the earth and so always appeared near the sun, As the earth passed Mars, Jupiter, and Saturn during opposition, the planets would appear to undergo retrograde motion.
What are inferior planets?
planets closer to the sun than earth
What are superior planets?
planets closer to earth than the sun
Can inferior planets ever reach an elongation of 180 degrees?
no
How do we tell apart superior and inferior planets by their elongation?
An inferior planet can never reach opposition while a superior planet can
Why did Copernicus never speak about Neptune, Uranus, and Pluto?
They were not discovered by then
What is a sidereal period?
The time it takes to complete an orbit
What is the synodic period?
the time it takes for a planet to make a complete cycle of elongation configurations
How can you measure the synodic period using opposition?
Measure the time it takes for the planet to go from one opposition to the next
How can you measure the synodic period using the greatest western elongation?
we can record the time it takes to start at and then return to its greatest western elongation
How did Copernicus show the relationship of the synodic period of a planet (S), the sidereal period of the planet (P), and the sidereal period of the earth (E)?
For superior planets: 1/S = 1/E - 1/P, For inferior planets 1/S = 1/P - 1/E
What is the sidereal period of the earth?
356.25 days
