Week 1 Flashcards
What is our view of the universe?
With the naked eye, we can see the moon, planets, just over 2,000 stars and the Milky Way galaxy.
An object’s ______ (above horizon) and ______ (along horizon) specify its location in your local sky.
An object’s altitude (above horizon) and direction (along horizon) specify its location in your local sky.
zenith
The point directly above an observer’s head. 90 degrees of altitude.
meridian
A line directly north that travels through the zenith to directly south.
The Celestial Sphere
An imaginary sphere surrounding earth upon which we map the night sky. Stars at different distances all appear to lie on the celestial sphere.
What is the ecliptic?
The ecliptic is the sun’s apparent path through the celestial sphere.
What are the north and south celestial poles?
The north and south celestial poles are projections of Earth’s poles onto the sky.
What is the celestial equator?
The celestial equator is a projection of the Earth’s equator onto the sky.
Latitude versus Longitude
Latitude is position north or south of the equator. Longitude is position east or west of the prime meridian.
Does the sky vary with latitude or with longitude?
The sky varies with latitude.
Your latitude equals the altitude of ______
Your latitude equals the altitude of the celestial pole in your hemisphere.
The distance between two points on a sphere is an ______.
The distance between two points on a sphere is an angle.
Angular Measurements
A full circle = 360 degrees. One degree equals 60 arcminutes. One arcminute equals 60 arcseconds.
What is a constellation?
A constellation is a region of the sky.
How many constellations fill the entire sky?
88.
Formula for Angular Size
Angular Size = Physical Size * (360 degrees)/(2pi * distance)
How does the appearance of an object’s angular size change at varying distances?
An object’s angular size appears smaller if it is farther away. Likewise, an object’s angular size appears larger if it is closer.
Why do stars rise and set?
Earth rotates west to east, so stars appear to circle from east to west.
Our view of star paths:
Our view is complicated by the fact that we aren’t observing the sky from the north pole. We see the sky rotate around the North Celestial Pole, NOT around our local zenith.
Circumpolar
A circumpolar star does not cross the horizon and is always visible in the sky near the celestial pole.
