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