Chapter 2: Discovering the Universe for Yourself Flashcards
What is a constellation?
A region of the sky with well defined borders.
What is the cellestial sphere?
The illusion of the stars appearing to be close to one another on a sphere that encompasses the earth.
What is the north celestial pole?
The point directly over the earth’s north pole.
What is the south celestial pole?
The point directly over the earth’s north pole.
What is the celestial equator?
A projection of earths equator into space, making a complete circle around the celestial sphere.
What is the ecliptic?
The path that the sun follows as it appears to circle around the celstial sphere.
What is the local sky?
The sky as seen from where you are standing.
At what angle does the ecliptic cross the celestial equator?
23.5 Degrees as that is the tilt of earth’s axis.
What is the zenith?
The point directly overhead of an observer.
What is the meridian?
An imaginary half circle stretching from the horizon die south, through the zenith, to the horizon due north.
What is an azimuth?
The direction of an object in the local sky that is measured in degrees clockwise from due north.
How many arcminutes are in a degree?
60’
How many arcseconds are in an arcminute?
60”
What makes a star circumpolar?
The star remains above the horizon all day.
What measurement is the altitude of the celestial pole in your sky equal to?
Your latitude on earth.
Why do we have seasons?
The tilt of earth’s axis results in more direct sunlight for longer periods of time during the summer and less direct sunlight for shorter periods of time during the winter.
What is precession?
The gradual wobble that alters the orientation of Earth’s axis in space.
How long is the lunar cycle?
29.5 days
If the moon is at it’s highest point at midnight, what phase is it in?
Full moon
If the moon is at it’s highest point before dawn, what phase is it in?
Waning Gibbous
If the moon is at it’s highest point at sunrise, what phase is it in?
Third quarter
If the moon is at it’s highest point at mid-morning, what phase is it in?
Waning Crescent
If the moon is at it’s highest point noon, what phase is it in?
New moon
If the moon is at it’s highest point at mid-afternoon, what phase is it in?
Waxing crescent
If the moon is at it’s highest point sun-set, what phase is it in?
First quarter
If the moon is at it’s highest point late evening, what phase is it in?
Waxing Gibbous
Why can’t we see a new moon?
The far side of the moon is getting all the light.
What is a lunar eclispse
When the earth lies directly between the sun and moon, so the earth’s shadow falls on the moon.
What is a solar eclispse?
When the moon lies directly between the sun and earth, so the moon’s shadow falls on earth.
What is a node in the moon’s orbit?
The parts of the moons orbit when the moon crosses the ecliptic.
When can a solar eclipse occur?
When the moon is new and is passing very close to a node.
When can a lunar eclipse occur?
When the moon is full and passing very close to a node.
What is an umbra during an eclipse.
Where sunlight is completely blocked.
What is a penumbra during an eclipse.
Where sunlight is partially blocked.
What is a total lunar eclipse?
When the moon passes through earth’s umbra.
What is a partial lunar eclipse?
When part of the moon passes through the umbra.
What is a penumbral lunar eclipse?
When the moon passes through only the earth’s penumbra.
What is a total solar eclipse?
When the moon’s umbra covers part of the earth (and the observer is standing within it.)
What is a annilar eclipse?
Occurs when the moon’s umbra does not reach earth’s surface.
What is a partial solar eclipse?
When the moon’s penumbra cover’s part of earth (and the observer is standing within it.)
What is the saros cycle?
The combination of the changing dates of eclipse seasons and the lunar phases.
