Midterm Flashcards
(44 cards)
What is the path of the planets we can see from the naked eye relative to?
The background stars
What is it called when the motion of the planets relative to the background stars change direction?
Retrograde motion
What is Kepler’s first law?
The orbit of each planet around the Sun is an ellipse, and the Sun is at one focus of the ellipse
What is Kepler’s second law?
As a planet moves around its orbit, a line from the planet to the Sun sweeps out equal area in equal time.
What is an ellipse?
The shape of a planet’s orbit is a closed, symmetric curve shaped like an oval. The sum of the distances from two foci to any point on the ellipse is a constant.
What is eccentricity?
A measure of how much an orbit deviates from circular. A perfectly circular orbit has an eccentricity of zero; higher numbers indicate more elliptical orbits. The least eccentric orbits are Neptune, Venus and Earth.
What is the semi major axis?
One half the length of the longest dimension of an ellipse and equal to the distance from the center of the ellipse to one end of the ellipse. It is also the average distance of a planet from the Sun at one focus.
What is the point on a planet’s orbit that is farthest from the sun?
Aphelion
What is the point on a planet’s orbit that is closest to the sun?
Perihelion
What is the celestial sphere?
2d universe seen across 2d in the sky from our perspective/how things move in the sky. North and South poles extend out to the North and South celestial poles, equator extends to the celestial equator.
What is the zenith?
The spot directly overhead of the viewer.
What is the horizon?
The imaginary plane where the sky meets the earth.
What is the meridian?
The line form the due South horizon through the zenith to the due North horizon.
What is the horizon diagram?
Imaginary sphere
What is circumpolar?
A star, as viewed from a given latitude on Earth, that never sets below the horizon due to its apparent proximity to one of the celestial poles.
What does the sun do on the equinox?
Rises in the east, sets in the west, with 12 daylight hours.
When is the highest path of the sun?
June 21st. The sun rises and sets at the most extreme north.
When is the lowest path of the sun?
December 21st. The sun rises and sets at the most extreme south.
Where can the sun be seen directly overhead, at the zenith?
In the tropics, at a latitude of 23.5 or less.
Where are shadows always cast?
On the opposite side of the sun.
What is the longest shadow that will be cast by the sun?
Noon on the winter solstice
Where will the shadow be cast when the sun is at its zenith?
No shadow
What do you call the orbit of the earth around the sun?
An ellipse
What impacts the seasons?
The tilt of the earth
